An efficient irrigation planting method for isatis indigotica and soybean intercropping

Abstract

The application belongs to the technical field of interplanting mode on root morphological characteristics and yield analysis, in particular to an efficient irrigation planting method for isatis indigotica and soybean interplanting, which comprises the following steps: step one, selecting test field: field test is carried out in May-October, 2023 in Hongshuihe Management Office Yimin Irrigation Test Station in Minle County, Zhangye City, Gansu Province, which is a representative basic irrigation test center in the northwest cold and arid region; step two, test design: the test is a double-factor test, a total of 8 treatments, soil moisture is set in two gradients, W1 and W2, W1 is soil moisture content of 55%-65% of field capacity, W2 is soil moisture content of 70%-80% of field capacity; interplanting modes are single isatis indigotica, single soybean, isatis indigotica 6 rows and soybean 6 rows, isatis indigotica 12 rows and soybean 6 rows, respectively marked as M1, M2, M3 and M4; the test has a total of 8 treatments, 3 groups of repetitions, a total of 24 plots; the soil moisture control depth of film mulching drip irrigation is 60cm; step three, determination index and analysis.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of interplanting mode on root morphological characteristics and yield analysis, and particularly relates to an efficient irrigation planting method for isatis indigotica and soybean interplanting. BACKGROUND

[0002] Isatis indigotica is a plant of Brassicaceae. At present, the researches on isatis indigotica at home and abroad mainly focus on the chemical components and pharmacological activities of isatis indigotica and daqingye, content determination, preparation and process, and the researches on irrigation modes in the planting process of isatis indigotica mainly focus on the influence on yield.

[0003] The correct agricultural production strategy should be to increase crop production and not damage the sustainable productivity of the land, and biological nitrogen fixation can meet both purposes. A reasonable interplanting mode can significantly improve the light energy utilization rate and water use efficiency of crops, improve the rhizosphere microenvironment, and improve the stress resistance of plants, thereby increasing yield and quality. Under the interplanting mode, natural resources such as light, heat, water and air can be fully utilized, and production costs can be reduced, thereby maximizing economic benefits.

[0004] Isatis indigotica has also been involved in interplanting: As early as 2005, Li Xiangdong proposed the planting points of apricot interplanting with isatis indigotica, Huang Yong et al. compared the agronomic traits, yield and economic benefit differences of isatis indigotica and corn under different interplanting modes, and found that interplanting isatis indigotica and corn can significantly improve economic benefits, and the best benefit is obtained when isatis indigotica and corn are interplanted in a 6:2 mode. Chen Hui et al. found that the planting mode of isatis indigotica interplanted with Pachysandra terminalis can at least achieve an increase of 1500 yuan per mu, which is a high-quality and efficient cultivation technology. In the interplanting experiment of mustard type spring rape and isatis indigotica, Wang Ruixia et al. found that the two crops with large differences in plant height can effectively provide shade for isatis indigotica at the seedling stage, increase the air flow in the field, create more marginal benefits, promote yield increase, interplanting of deep-rooted crops and shallow-rooted crops can realize the complementation of root nutrition, and the income of mustard type spring rape and isatis indigotica under the interplanting mode of row ratio 2:4 is higher than that under the single planting mode.

[0005] Leguminous crops in the planting system fix atmospheric free nitrogen by appropriate means, and interplanting of cruciferous crops and legumes has also been tested, but the comprehensive research on isatis indigotica and soybean interplanting under water stress conditions is relatively blank.

[0006] In the field of intercropping, Wang believes that the longer growing season and incomplete ground cover are the main factors that lead to higher water consumption in wheat-corn intercropping than in monocropping. Water-saving measures can be implemented during the wheat's booting or grain filling stage in wheat-corn intercropping to conserve irrigation water. Hu et al. found that although intercropping increased crop yield, it also consumed a large amount of water and required higher inputs, and further research is needed for its application in arid regions. Tang Mingming explored the effects of different crop combinations, row spacing, and planting density on soybean growth and yield through field experiments and large-scale simulation studies. Lili Mao believes that the edge row effect is the main reason for the yield advantage of intercropping crops. His research results show that corn and pea intercropping has higher land use efficiency than monocropping, and film mulching can effectively reduce crop water use. Yang C believes that in areas where irrigation is the main source of water, especially in oasis areas, alternate irrigation is an effective improvement of wheat-corn intercropping irrigation technology, and AI processing can improve the total yield and WUE of wheat and corn. Ren J believes that potato-pea intercropping systems improve land productivity and system-level water use efficiency. An Jinfeng found that after intercropping soybeans with short-stem crops, due to differences in plant type and ecological characteristics, crops interact and complement each other, have higher chlorophyll content and yield than monocropping, and have considerable economic benefits. He also pointed out that the optimal range of soybean height for intercropping is 70-90 cm.

[0007] Modern agriculture should no longer simply aim for high yields. In the process of exploring efficient water-saving patterns for isatis indigotica, introducing crop competition and symbiotic relationships through intercropping can improve crop yield and economic benefits per unit of water, which is the essence of efficient water-saving and the significance of intercropping. SUMMARY

[0008] The present application provides a kind of efficient irrigation planting method of isatis indigotica and soybean intercropping, which can effectively solve the problems existing in the prior art.

[0009] To achieve the above object, the present application provides the following technical scheme:

[0010] An efficient irrigation planting method of isatis indigotica and soybean intercropping, characterized in that it comprises the following steps:

[0011] Step 1: Select test site

[0012] The field test was conducted in Hongshuihe Management Office Yimin Irrigation Test Station in Minle County, Zhangye City, Gansu Province from May to October 2023. The station is a representative basic irrigation test center in the cold and arid regions of the northwest. The test area has good water and fertilizer retention properties. The test soil has a field moisture capacity of 24% (mass moisture content) and a pH value of about 7.2, which is medium loam soil with a soil bulk density of 1.46 g·cm -3, groundwater depth > 20 m, no salinization phenomenon, plough layer 0-60 cm. The Hongshuihe River Management Office Yimin Irrigation Test Station has a weather monitoring station that can directly obtain rainfall, air temperature, atmospheric relative humidity, and surface temperature data. The average annual temperature in 2022 was 5.6°C, 1°C higher than the average annual temperature. The total sunshine hours were 2768.1 hours, and the annual sunshine rate was 62%. During the entire growth period, the total rainfall was 107.0 mm, which was relatively dry compared to previous years;

[0013] Step two, test design

[0014] The test is a two-factor test, with a total of 8 treatments. Soil moisture is set at two levels: W1 (soil moisture content is 55%-65% of field water capacity) and W2 (soil moisture content is 70%-80% of field water capacity). The intercropping patterns are single Isatis indigotica, single Glycine max, I. indigotica || G. max (6 rows: 6 rows), and I. indigotica || G. max (12 rows: 6 rows), respectively, denoted as M1, M2, M3, and M4. The test has 8 treatments, 3 replicates, and 24 plots. The soil moisture control depth for drip irrigation under mulch is 60 cm.

[0015] Table 1: Test treatments for I. indigotica and G. max intercropping (using the growth period of I. indigotica as an example)

[0016]

[0017] Step three, determination of indicators and analysis, as follows:

[0018] 1. Biological characteristics indicators

[0019] After I. indigotica and G. max enter the seedling stage, randomly select 3 seedlings with uniform growth and representative of the average growth state of the plot in each plot, and at the end of their respective growth periods, measure the height from the base of the plant to the growth point with a steel tape with a precision of 1 mm, and measure the stem diameter at the junction of the aboveground and underground parts with an electronic vernier caliper. Take the average of the leaf number of 3 plants as the value at that growth stage.

[0020] At the end of each growth period of I. indigotica, randomly select 3 plants with uniform growth and good representation in the plot using the destructive sampling method. Measure the biological indicators of the aboveground leaves and underground roots of I. indigotica. Use the rectangular method to measure the leaf area of I. indigotica, record the data, and then place the fresh samples in a 105°C ventilated drying oven to kill the greenness. Dry until constant weight, and then record the mass of each part of the sample. Wash and dry the roots of I. indigotica and G. max to measure the fresh weight.

[0021] Leaf Area Index (LAI) is the ratio of the total leaf area per unit ground area to that area, and is a dimensionless indicator. The mathematical expression is:

[0022] LAI = leaf area sum / ground area (1)

[0023] Each plot selects 3 plants of Isatis indigotica or soybean (3 plants of each crop in intercropping plot), and the fleshy roots of Isatis indigotica are completely dug out to measure root length, root thickness, root weight, lateral root number, plant height and leaf weight. The average value is measured, and finally the yield per hectare of Isatis indigotica is converted according to the planting area and actual planting number of the plot;

[0024] 2. Photosynthetic index

[0025] During the growth period of Isatis indigotica, typical days with clear weather and less clouds are selected, and the stomatal conductance Gs, net photosynthetic rate Pn, transpiration rate Tr and intercellular carbon dioxide concentration Ci of Isatis indigotica leaves are measured by LI-6400 portable photosynthetic instrument from 9:00 to 11:00 in the morning; 3 plants of Isatis indigotica with uniform growth are randomly selected in each plot, and the medium-sized leaves without obvious damage, diseases and insect pests and with similar morphology and similar leaf age, which can represent the average physiological state of the whole plant, are measured in vivo (to avoid the water supply shortage after the leaves are separated from the plants, which leads to the weakening of cell activity and affects photosynthesis);

[0026] The SPAD portable photosynthetic instrument is used to measure the chlorophyll content of Isatis indigotica and soybean leaves during each growth period, 9 plants are randomly selected in each plot, and 3 green leaves are randomly measured for each plant. The selection principle of leaves is consistent with the selection idea of Li-6400 measured leaves;

[0027] 3. Soil moisture content

[0028] Before sowing, after film mulching, before irrigation, before and after rainfall, use a soil drill with a depth of 100 cm to take soil in layers, remove the surface soil, and take 20 cm of soil each time; the soil moisture content is measured by drying method; since Zhangye City no longer measures evaporation in Sunan, Minle and Linze since 2014, the corresponding parameters are lacking, so the previous experimental research is followed, and the soil is taken and measured every 7-10 days to ensure timely adjustment of the water gradient; the measurement range is 0-100 cm. The root system of Isatis indigotica is deeper, and the root system of soybean is shallower than that of Isatis indigotica. The planned range of the wet layer is 0-60 cm, and the average value of the soil moisture content in the 0-60 cm soil layer is taken as the soil irrigation volume. Before July 19 (soybean branching period), because the crop root system is shallow, the planned range of the soil layer is 0-40 cm; when the soil moisture content of the soil layer is lower than the lower limit of each water gradient in Table 1, irrigation is carried out to supplement water, and the irrigation volume is supplemented to the upper limit of the soil moisture content of the plot. The precision of the water meter is 0.0001 m 3 The irrigation volume of the water meter test plot is measured, and the irrigation volume calculation formula is:

[0029] W = 10γH p(θ i -θ j ) (2)

[0030] In the formula: W is the irrigation amount, mm; γ is the soil bulk density, g·cm -3 ; H p is the planned depth of the wet layer, cm; θ i is the upper limit of the soil control water content, %; θ j is the measured soil mass water content before irrigation, %;

[0031] 4. Water use efficiency

[0032] (1) Water consumption

[0033] The water consumption of Isatis indigotica and soybean during the growth period was calculated by the water balance method:

[0034] ET = (W0-W f ) + P + K + M-C (3)

[0035] In the formula: ET is the water consumption of Isatis indigotica and soybean, mm; W0 is the planned wet layer water storage at the beginning of the growth period, mm; W f is the planned wet layer water storage at the end of the growth period, mm; P is the effective precipitation during the growth period of the crop (P > 5 mm), mm; M is the irrigation amount, mm; K is the deep soil water recharge, mm; C is the deep soil water seepage, mm;

[0036] The groundwater depth at Yimin Irrigation Experiment Station is greater than 20 m, and the groundwater recharge is 0, so K = 0; the designed irrigation water amount is lower than the field water holding capacity, and no deep seepage will occur, so C = 0.

[0037] Water consumption intensity (mm / d) = water consumption / growth period days (4)

[0038] Water consumption modulus (%) = stage water consumption / total growth period water consumption (5)

[0039] (2) Water use efficiency

[0040] The water use efficiency WUE (kg / hm 2 ·mm -1 ) of Isatis indigotica and soybean is calculated by the formula:

[0041] WUE = Y / ET (6)

[0042] In the formula: Y refers to the yield of Isatis indigotica (or soybean), kg / hm 2 ; ET is the water consumption of Isatis indigotica (soybean) during the whole growth period, mm;

[0043] Irrigation water use efficiency IWUE (kg / hm 2·mm -1 ) Calculation formula is:

[0044] IWUE = Y / I (7)

[0045] In the formula: Y is the yield of Isatis indigotica Fort. (or soybean), kg / hm 2 ; I is the irrigation amount of Isatis indigotica Fort., mm;

[0046] 5. Intercropping benefit

[0047] (1) Land equivalent ratio

[0048] Land equivalent ratio (LER) refers to the single-crop land area required to produce the same yield as the yield obtained by intercropping two or more crops on a unit area, which is used to measure whether intercropping has yield advantage:

[0049] LER = (Y iw / Y sw )+(Y is / Y ss ) (8)

[0050] In the formula: Y iw is the yield of crop A on the total intercropping area, kg / hm 2 ; Y is is the yield of crop B on the total intercropping area, kg / hm 2 ; Y sw is the yield of crop A in single cropping, kg / hm 2 ; Y ss is the yield of crop B in single cropping, kg / hm 2 ; When LER>1, it indicates that intercropping has an advantage, and when LER<1, it indicates that intercropping has a disadvantage;

[0051] (2) Water equivalent ratio

[0052] In field trials, water equivalent ratio (WER) reflects the crop yield that can be obtained per unit of water input, and measures whether intercropping has a water advantage over single cropping:

[0053] WER = (WUE iw / WUE sw )+(WUE is / WUE ss ) (9)

[0054] In the formula: WUE iw is the water use efficiency of crop A in intercropping treatment, kg / (hm 2 ·mm); WUE is is the yield water use efficiency of crop B in intercropping treatment, kg / (hm 2 ·mm); WUEsw Water use efficiency of crop A in monoculture, kg / (hm 2 ·mm); WUE ss Water use efficiency of crop B in monoculture, kg / (hm 2 ·mm). Similarly, when WER>1 indicates that intercropping has a water advantage, when WER<1 indicates that intercropping has a water disadvantage;

[0055] (3) Interspecific competition

[0056] The interspecific competition of crops indicates the relative competition ability of one crop relative to another crop, and the calculation formula is:

[0057] Ag=Y iw / (Y sw ×P w )-Y is / (Y ss ×P s ) (10)

[0058] In the formula: Ag is the resource competition of crop A relative to crop B; Y iw is the yield of crop A on the total intercropping area, kg / hm 2 ; Y is is the yield of crop B on the total intercropping area, kg / hm 2 ; Y sw is the yield of crop A in monoculture, kg / hm 2 ; Y ss is the yield of crop B in monoculture, kg / hm 2 ; P w is the proportion of crop A in intercropping, P s represents the proportion of crop B in intercropping. When Ag>0, it indicates that the competition of crop A is stronger than that of crop B, and when Ag<0, it indicates that the competition of crop A is weaker than that of crop B;

[0059] (4) Economic benefits

[0060] After intercropping of Isatis indigotica and soybean, the total input per mu of land will inevitably increase, but whether the intercropping mode can realize cost reduction and benefit increase compared with the monoculture mode can be calculated according to the following formula to calculate the unit economic benefit output by the intercropping mode:

[0061] W 效益 =W 产出 -W 投入 (11)

[0062]

[0063] W 投入 =T 人工 +T 机械 +T肥料 +T 灌溉 +T 除草 +T 农药 (13)

[0064] In the formula: W 效益 is the economic benefit cost of crops per unit area, yuan; W 产出 is the economic output cost of crops per unit area, yuan; W 投入 is the economic input cost of crops per unit area, yuan; S i is the yield of crops per unit area, kg / hm 2 ; Z i is the minimum sales price of the crop in the market (yuan / hm 2 ); T is the input cost per unit area, yuan / hm 2 .

[0065] The present application determines the influence degree of intercropping mode on the photosynthetic characteristics and biomass quality of Isatis indigotica, as follows:

[0066] (1) The intercropping mode promotes the growth of plant height, root length and root diameter of Isatis indigotica, and is beneficial to the growth and development of the root of Isatis indigotica. The intercropping mode improves the photosynthetic characteristics of Isatis indigotica. Under sufficient irrigation conditions, the net photosynthetic rate (Pn) under the intercropping mode is significantly higher than that under the monocropping mode. The intercropping mode effectively slows down the downward trend of stomatal conductance (Gs) and transpiration rate (Tr), which is beneficial to maintaining high water use efficiency of crops under water stress conditions.

[0067] (2) In terms of biomass and quality, the intercropping mode improves the biomass of Isatis indigotica and improves the content of effective components of Isatis indigotica, and the quality of crops is better. The intercropping mode improves the economic output of crops and also enhances the market competitiveness of Isatis indigotica.

[0068] (3) The water-saving benefit analysis shows that under the condition of light water deficit, the intercropping mode realizes the effect of water-saving, stable yield and quality improvement by optimizing water use efficiency and irrigation water use efficiency. This provides an effective strategy for agricultural water resource management in the cold and cool irrigation area of Hexi. The economic benefit evaluation result reveals that the monocropping of Isatis indigotica has high economic benefit under the condition of light water deficit, and the intercropping mode increases the water consumption, but correspondingly improves the single plant dry weight and quality of Isatis indigotica, showing the economic benefit of water-saving, stable yield and quality improvement.

[0069] (4) Considering the actual local water resources, the form of insufficient irrigation is the main mode of local crop planting irrigation water. When large-scale planting is promoted, it cannot be guaranteed that isofabrine can get sufficient irrigation water throughout the whole growth period. Limited water needs to be used to improve the biomass and quality of isofabrine as much as possible and promote income, that is, under the condition of light water deficit, the 2:1 intercropping planting mode can play the advantages of intercropping with legumes and improve the quality of isofabrine. At this time, it has better water use efficiency and irrigation water use efficiency, plays a role in water saving, stable yield and quality improvement, and is the optimal planting mode under the intercropping planting mode of isofabrine and soybean. BRIEF DESCRIPTION OF DRAWINGS

[0070] Figure 1 Fig. 1 is a graph of the biological characteristics of isofabrine in the embodiment of the present application;

[0071] Figure 2 Fig. 1 is a graph of the biological characteristics of isofabrine in the embodiment of the present application;

[0072] Figure 3 Fig. 1 is a graph of the biological characteristics of isofabrine in the embodiment of the present application; DETAILED DESCRIPTION

[0073] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0074] Example 1

[0075] A high-efficiency irrigation planting method for intercropping isofabrine and soybean, characterized in that it comprises the following steps:

[0076] Step 1, selecting a test site

[0077] The field test was carried out in Hongshuihe Management Office Yimin Irrigation Test Station in Minle County, Zhangye City, Gansu Province from May to October 2023. The station is a representative basic irrigation test center in the northwest cold and arid region. The test area has good water and fertilizer retention properties. The test soil has a field moisture capacity of 24% (mass moisture content), a pH value of about 7.2, and a soil bulk density of 1.46 g·cm -3, groundwater depth > 20 m, no salinization phenomenon, plough layer 0-60 cm. The Hongshuihe River Management Office Yimin Irrigation Test Station has a weather monitoring station that can directly obtain rainfall, air temperature, atmospheric relative humidity, and surface temperature data. The average annual temperature in 2022 was 5.6°C, 1°C higher than the average annual temperature. The total sunshine hours were 2768.1 hours, and the annual sunshine rate was 62%. During the entire growth period, the total rainfall was 107.0 mm, which was relatively dry compared to previous years;

[0078] Step two, test design

[0079] The test is a two-factor test, with a total of 8 treatments. Soil moisture is set at two levels: W1 (soil moisture content is 55%-65% of field water capacity) and W2 (soil moisture content is 70%-80% of field water capacity). The intercropping patterns are single Isatis indigotica, single Glycine max, I. indigotica || G. max (6 rows: 6 rows), and I. indigotica || G. max (12 rows: 6 rows), respectively, denoted as M1, M2, M3, and M4. The test has 8 treatments, 3 replicates, and a total of 24 plots. The soil moisture control depth for film mulching drip irrigation is 60 cm.

[0080] Step three, determination of indicators and analysis, as follows:

[0081] 1. Biological characteristics indicators

[0082] After I. indigotica and G. max enter the seedling stage, 3 seedlings with uniform growth and representative of the average growth state of the plot are randomly selected in each plot. At the end of the respective growth period, the height from the base of the plant to the growth point is measured with a steel tape with a precision of 1 mm, and the stem diameter at the junction of the aboveground and underground parts is measured with an electronic vernier caliper. The average number of leaves measured from 3 plants is recorded as the value at that growth stage.

[0083] At the end of each growth period of I. indigotica, 3 plants with uniform growth and good representation are randomly selected in the plot using the destructive sampling method. The biological indicators of the aboveground leaves and underground roots of I. indigotica are measured, the leaf area is measured using the rectangular method, and the fresh samples are placed in a 105°C ventilated drying oven for fixation and drying until constant weight. The mass of each part of the sample is recorded. The roots of I. indigotica and G. max are washed and dried to measure the fresh weight.

[0084] Leaf Area Index (LAI) is the ratio of the total leaf area per unit ground area to that area, which is a dimensionless index. The mathematical expression is:

[0085] LAI = Total Leaf Area / Ground Area (1)

[0086] Each plot selects 3 plants of isatis indigotica or soybean (each crop selects 3 plants in intercropping plot), isatis indigotica needs to be completely dug out its fleshy root, and the root length, root thickness, root weight, lateral root number, plant height and leaf weight are measured; the average value is taken, and finally the yield per hectare of isatis indigotica is converted according to the plot planting area and the actual planting number of plants;

[0087] 2. Photosynthetic index

[0088] During the growth period of isatis indigotica, on a typical day with clear weather and less cloud, the stomatal conductance Gs, net photosynthetic rate Pn, transpiration rate Tr and intercellular carbon dioxide concentration Ci of isatis indigotica leaves are measured by using LI-6400 portable photosynthetic instrument from 9:00 to 11:00 in the morning; 3 plants of isatis indigotica with uniform growth are randomly selected in each plot, and the medium-sized leaves without obvious damage, diseases and insect pests and with similar morphology and similar leaf age, which can represent the average physiological state of the whole plant, are measured in vivo (to avoid the water supply shortage of leaves after being separated from the plant, which leads to the weakening of cell activity and thus affects photosynthesis);

[0089] The SPAD portable photosynthetic instrument is used to measure the chlorophyll content of isatis indigotica and soybean leaves during each growth period, 9 plants are randomly selected in each plot, and 3 green leaves of each plant are randomly measured; the selection principle of leaves is consistent with the selection idea of Li-6400 for measuring leaf photosynthesis;

[0090] 3. Soil water content

[0091] Before sowing, after film mulching, before irrigation, before and after rainfall, the soil is taken by soil drill with a depth of 100 cm, and the surface soil is removed, and 20 cm of soil is taken each time; the soil water content is measured by drying method; since Zhangye city no longer measures evaporation in Sunan, Minle and Linze since 2014, the corresponding parameters are lacking, so the previous experimental research is followed, and the soil is taken and measured every 7-10 days to ensure timely adjustment of the water gradient; the measurement range is 0-100 cm. The root system of isatis indigotica is deeper, and the root system of soybean is shallower than that of isatis indigotica, so the planned range of the wet layer is 0-60 cm, and the average value of the soil water content in the 0-60 cm soil layer is taken as the soil irrigation volume; before July 19 (branching period of soybean), the soil layer is planned to be wetted to 0-40 cm because the crop root system is shallow; when the soil water content of the soil layer is lower than the lower limit of each water gradient in table 1, irrigation is carried out to supplement water, and the irrigation volume is supplemented to the upper limit of the soil water content of the plot. The accuracy of the water table metering test plot is 0.0001 m 3 The irrigation volume of the water table metering test plot is calculated by the formula:

[0092] W = 10γH p (θ i -θ j ) (2)

[0093] In the formula, W is the irrigation amount, mm; γ is the soil bulk density, g·cm -3 ; H p is the planned depth of the wet layer, cm; θ i is the upper limit of the soil control water content, %; θ j is the measured soil mass water content before irrigation, %;

[0094] 4. Water use efficiency

[0095] (1) Water consumption

[0096] The water consumption of Isatis indigotica and soybean during the growth period was calculated by the water balance method:

[0097] ET = (W0-W f ) + P + K + M - C (3)

[0098] In the formula, ET is the water consumption of Isatis indigotica and soybean, mm; W0 is the planned wet layer water storage at the beginning of the growth period, mm; W f is the planned wet layer water storage at the end of the growth period, mm; P is the effective precipitation (P > 5 mm) during the growth period of the crop, mm; M is the irrigation amount, mm; K is the deep soil water recharge, mm; and C is the deep soil water leakage, mm.

[0099] The groundwater depth at Yimin Irrigation Experiment Station is greater than 20 m, and the groundwater recharge is 0, so K = 0; the designed irrigation water amount is lower than the field water holding capacity, and no deep leakage will occur, so C = 0.

[0100] Water consumption intensity (mm / d) = water consumption / growth period days (4)

[0101] Water consumption modulus (%) = stage water consumption / total growth period water consumption (5)

[0102] (2) Water use efficiency

[0103] The water use efficiency WUE (kg / hm 2 ·mm -1 ) of Isatis indigotica and soybean is calculated by the formula:

[0104] WUE = Y / ET (6)

[0105] In the formula, Y refers to the yield of Isatis indigotica (or soybean), kg / hm 2 ; and ET is the water consumption of Isatis indigotica (soybean) during the whole growth period, mm.

[0106] The irrigation water use efficiency IWUE (kg / hm 2 ·mm -1 ) is calculated by the formula:

[0107] IWUE = Y / I (7)

[0108] Where: Y is the yield of Isatis indigotica Fort. (or soybean), kg / hm 2 ; I is the irrigation amount of Isatis indigotica Fort., mm;

[0109] 5. Intercropping benefit

[0110] (1) Land equivalent ratio

[0111] Land equivalent ratio (LER) refers to the land area required for producing the same yield in monoculture when two or more crops are intercropped in unit area, and is used to measure whether intercropping has yield advantage:

[0112] LER = (Y iw / Y sw )+(Y is / Y ss ) (8)

[0113] Where: Y iw is the yield of crop A in the total intercropped area, kg / hm 2 ; Y is is the yield of crop B in the total intercropped area, kg / hm 2 ; Y sw is the yield of crop A in monoculture, kg / hm 2 ; Y ss is the yield of crop B in monoculture, kg / hm 2 ; When LER > 1, it indicates that intercropping has advantage, and when LER < 1, it indicates that intercropping has disadvantage;

[0114] (2) Water equivalent ratio

[0115] In field experiment, water equivalent ratio (WER) reflects the yield of crops that can be obtained per unit of water input, and measures whether intercropping has water advantage than monoculture:

[0116] WER = (WUE iw / WUE sw )+(WUE is / WUE ss ) (9)

[0117] Where: WUE iw is the water use efficiency of crop A in intercropping, kg / (hm 2 ·mm); WUE is is the yield water use efficiency of crop B in intercropping, kg / (hm 2 ·mm); WUE sw is the water use efficiency of crop A in monoculture, kg / (hm2 · mm); WUE ss kg / (hm 2 · mm) of crop B in monoculture. Similarly, when WER > 1 indicates that intercropping has a water advantage, and when WER < 1 indicates that intercropping has a water disadvantage;

[0118] (3) Interspecific competition

[0119] The interspecific competition of crops indicates the relative competition ability of one crop relative to another crop, and the calculation formula is:

[0120] Ag = Y iw / (Y sw × P w ) - Y is / (Y ss × P s ) (10)

[0121] In the formula: Ag is the resource competition of crop A relative to crop B; Y iw is the yield of crop A on the total intercropping area, kg / hm 2 ; Y is is the yield of crop B on the total intercropping area, kg / hm 2 ; Y sw is the yield of crop A in monoculture, kg / hm 2 ; Y ss is the yield of crop B in monoculture, kg / hm 2 ; P w is the proportion of crop A in intercropping, P s represents the proportion of crop B in intercropping. When Ag > 0, it indicates that the competition of crop A is stronger than that of crop B, and when Ag < 0, it indicates that the competition of crop A is weaker than that of crop B;

[0122] (4) Economic benefits

[0123] After intercropping of Isatis indigotica and soybean, the total input per mu of land will inevitably increase, but whether the intercropping mode can realize cost reduction and benefit increase compared with the monoculture mode can be calculated according to the following formula to calculate the unit economic benefit output by the intercropping mode:

[0124] W 效益 = W 产出 - W 投入 (11)

[0125]

[0126] W 投入 = T 人工 + T 机械 + T 肥料 + T 灌溉 + t除草 +T 农药 (13)

[0127] wherein: W 效益 is the economic benefit cost of crops per unit area, yuan; W 产出 is the economic output cost of crops per unit area, yuan; W 投入 is the economic input cost of crops per unit area, yuan; S i is the yield of crops per unit area, kg / hm 2 ; Z i is the minimum sales price of the crops on the market (yuan / hm 2 ); and T is the input cost per unit area, yuan / hm 2 .

[0128] Example 2

[0129] 1. Influence on the biological characteristics of Isatis indigotica Fort.

[0130] Isatis indigotica Fort. has a simple structure and can be roughly divided into aboveground and underground parts. The plant height of Isatis indigotica Fort. increases with the advancing growth period and reaches the maximum value at the root maturation stage. At the seedling stage, the plant height of each treatment has little difference, and the effects of water and intercropping mode on the plant height are not significant (P>0.05). After entering the leaf nutrition stage, the plant height of Isatis indigotica Fort. grows rapidly, and the plant height of the 2:1 intercropping (2 rows of Isatis indigotica Fort.: 1 row of soybean, the same below) treatment M4W2 is the maximum, which is 34.30 cm. There is a significant difference between water and intercropping mode on the plant height (P<0.05), but the interaction effect is not significant (P>0.05). At the root growth stage, there is a very significant difference in the plant height between the intercropping modes (P<0.01), and the plant height trend is M4>M1>M2, and the interaction effect between groups is not significant (P>0.05). At the root maturation stage, the plant height reaches the maximum value, and the maximum value is in the M4W2 treatment, which is 37.75 cm. According to the change law of the plant height during the whole growth period, it can be known that, except for the seedling stage, the intercropping mode and water gradient have a significant effect on the plant height of Isatis indigotica Fort., and the growth trend is 2:1 intercropping>1:1 intercropping (1 row of Isatis indigotica Fort.: 1 row of soybean, the same below)>monocropping. The change of the plant height of Isatis indigotica Fort. at each growth stage is shown in Figure 1 a) Figure.

[0131] As Figure 1b) shows: seedling stage, the diameter of succulent root W2 > W1, the difference of succulent root diameter in water gradient is minimum in 2:1 intercropping mode, there is extremely significant difference in water gradient and intercropping mode (P<0.01), and the interaction is extremely significant (P<0.01). Under sufficient irrigation condition in leaf nutrient growth period, the diameter of succulent root of intercropping is not as good as monoculture, but under mild water deficit condition, 2:1 intercropping mode has the greatest benefit to the growth of the diameter of succulent root of Isatis indigotica, the diameter of succulent root of Isatis indigotica is between 8.14-12.16 mm in this period; the maximum diameter appears in sufficient irrigation mode and mild water deficit mode of monoculture planting mode, and intercropping mode shows stable yield benefit. In the growth period of succulent root of Isatis indigotica, under the same water condition, mild water deficit is beneficial to the growth of succulent root of Isatis indigotica, and water condition, intercropping mode and their interaction have extremely significant effect on the difference (P<0.01). In the mature period of succulent root, the diameter of succulent root of Isatis indigotica in 2:1 intercropping mode is the highest, compared with monoculture, water gradient, intercropping mode and their interaction have extremely significant effect on the difference of the diameter of succulent root (P<0.01). At this time, the law is: 2:1 intercropping is the largest, 1:1 intercropping is the second, and monoculture is the weakest. The length of succulent root of Isatis indigotica shows the trend of monoculture>2:1 intercropping>1:1 intercropping, and the length of succulent root of Isatis indigotica is better under mild water deficit condition, such as Figure 1 c) shows.

[0132] The number of Isatis indigotica leaves shows the trend of first increasing and then decreasing, and the overall performance is monoculture>2:1 intercropping>1:1 intercropping. In intercropping mode, the leaf under mild water deficit treatment is higher than that under sufficient irrigation treatment, which is contrary to the performance of monoculture, and water condition and intercropping mode have extremely significant effect on the difference (P<0.05). The length of succulent root of Isatis indigotica in each growth period is shown in Figure 1 d) shows.

[0133] During the whole growth period of Isatis indigotica, the leaf area index (LAI) shows the trend of first increasing and then decreasing, and reaches the highest level in the growth period of succulent root. The LAI value of Isatis indigotica is relatively low in seedling stage, and the LAI value of monoculture is higher than that of intercropping. In leaf nutrient growth period, the LAI value rises rapidly, and the LAI value of Isatis indigotica under intercropping mode is higher under certain water condition, and the effect of water condition, intercropping mode and their interaction on the difference is extremely significant (P<0.05). In the growth period of succulent root, the LAI value of each treatment decreases, and the LAI value of Isatis indigotica under intercropping mode increases under water stress condition, and the increase rate of M4W1 treatment is the highest. In the mature period of succulent root, the LAI value of Isatis indigotica decreases, and the LAI value of Isatis indigotica under intercropping mode decreases more greatly because soybean has been harvested at this time, and the decrease rate is less than half of that in leaf nutrient growth period; the overall performance trend is M1W2>M1W1>M4W1>M4W2>M3W2>M3W1, and the LAI change is shown in Figure 1 e) shows.

[0134] 2、Effect on the ratio of dry matter and root crown

[0135] The total dry weight of Isatis indigotica accumulated most in the leaf nutrition growth period, followed by the fleshy root growth period. After entering the fleshy root maturation period, the total dry matter accumulation decreased with the leaf abscission. The dry matter accumulation was overall single cropping > 2:1 intercropping > 1:1 intercropping, and the dry matter accumulation under light water deficit was better than that under sufficient irrigation. There was a significant difference (P<0.01) between planting patterns and a significant difference (P<0.05) between water gradients.

[0136] The root crown ratio of Isatis indigotica showed a gradual increasing trend during the whole growth period, reaching the highest level in the fleshy root maturation period, between 85.33% and 95.33%, while the root crown ratio in the seedling stage was only 13.33% to 24.67%, and in the leaf nutrition growth period, it was only in the range of 42.00% to 47.67%. The effective components of Isatis indigotica were effectively deposited during the fleshy root growth and maturation periods, and the overall performance was single cropping > 2:1 intercropping > 1:1 intercropping, and light water deficit was beneficial to increasing the root crown ratio of Isatis indigotica. In the seedling and leaf nutrition growth periods, water and planting patterns had a significant effect (P<0.01) on the difference, but after considering the fleshy root growth period, the difference mainly came from the water gradient (P<0.05). The interaction effect of water and planting patterns was not significant (P>0.05). The dry matter accumulation and root crown ratio of Isatis indigotica during each growth period are shown in Figure 2 .

[0137] 3、Effect on photosynthetic characteristics

[0138] Net photosynthetic rate reflects the plant's ability to actually accumulate organic matter under light conditions, and is an important indicator of plant photosynthetic efficiency

[28] .

[0139] The net photosynthetic rate (Pn) of Isatis indigotica gradually increased with the advancement of the growth period, and reached the highest level in the fleshy root growth period, and then fell in the fleshy root maturation period, showing a single peak curve of first increasing and then decreasing. Based on the overall change law of net photosynthesis during the whole growth period, intercropping patterns and water gradients had a significant effect on Isatis indigotica, and there was an interaction in the seedling stage, with the growth of 2:1 intercropping > 1:1 intercropping > single cropping. The net photosynthetic rate change graph during the growth period is shown in Figure 3 a) figure.

[0140] The stomatal conductance Gs showed a trend of gradual increase during the whole growth period of I. indigotica, and reached the highest level at the root maturation stage. The stomatal conductance value was relatively low at the seedling stage, and the difference was not large. During the leaf vegetative growth stage, the difference of stomatal conductance mainly came from the water gradient. During the root growth stage, the difference of stomatal conductance value between different treatments was also small. At the root maturation stage, the stomatal conductance of I. indigotica reached the highest level, and different planting modes would cause differences in stomatal conductance of I. indigotica. Water stress and intercropping mode could promote the stomatal conductance value of I. indigotica to the full irrigation level. The stomatal conductance value of I. indigotica at different growth stages is shown in Figure 3 b)。

[0141] During the whole growth period of I. indigotica, the transpiration rate Tr showed a trend of first increasing and then decreasing, and reached the highest level at the root growth stage. The transpiration rate of I. indigotica at the seedling stage was low, but the intercropping mode could improve the transpiration rate of I. indigotica at the seedling stage. During the leaf vegetative growth stage, the transpiration rate of I. indigotica increased significantly with the rapid growth of leaves. Under certain water conditions, the intercropping mode had a promoting effect on the transpiration rate of I. indigotica, but the influence of water on this difference was not significant (P>0.05). During the root growth stage, the transpiration rate of each treatment decreased, and the planting mode still had a promoting effect on the transpiration rate of I. indigotica. At the root maturation stage, the transpiration rate of I. indigotica decreased again, about half of that at the leaf vegetative growth stage, and the promoting effect of 1:1 intercropping mode on the transpiration rate was weaker than that of 2:1 intercropping mode. Under water stress conditions, the stress resistance of I. indigotica in the two intercropping modes was not as good as that of I. indigotica in monoculture, and the difference from the full irrigation level was large. The transpiration rate value of I. indigotica at different growth stages is shown in Figure 3 c)。

[0142] During the whole growth period of I. indigotica, the intercellular CO2 concentration Ci showed a trend of first decreasing and then increasing, and was at a high level in the seedling stage and decreased to a low value in the fibrous root growth stage. This was because the stomatal conductance was small, the net photosynthetic rate was low, and the leaf had weak carbon dioxide absorption capacity in the seedling stage. The intercropping mode had an effect on the utilization efficiency of Ci in the seedling stage of I. indigotica, and water deficit conditions could increase the transformation and utilization of Ci. In the leaf vegetative growth stage, with the increase of leaf growth, temperature, stomatal conductance and the increase of net photosynthetic rate of I. indigotica, the Ci concentration rapidly decreased in each treatment. In the full irrigation, the Ci of I. indigotica in the intercropping mode could be effectively transformed and utilized, but in the water deficit, the change of Ci value needed to be considered from many aspects. In the fibrous root growth stage, under water stress conditions, the 2:1 intercropping mode could slightly improve the transformation and utilization of Ci value, but the Ci value of the 1:1 intercropping mode increased. This was because the density of I. indigotica and soybean in the 1:1 intercropping mode was too large, and the stomatal conductance decreased with leaf abscission in the grain filling stage of soybean, which had a restraining effect on the photosynthetic transformation of I. indigotica. In the fibrous root maturation stage, the Ci value of I. indigotica increased, and the stomatal conductance Gs value was the largest at this time, but the weather turned cool and the light weakened, the net photosynthetic rate Pn of I. indigotica decreased significantly, the transformation ability decreased, and the efficiency of Ci participating in photosynthesis decreased. The Ci value change graph of I. indigotica in each growth period is shown in Figure 1. Figure 3 d).

[0143] During the whole growth period of I. indigotica, the relative chlorophyll content SPAD value showed an upward trend, and the SPAD value changed in the range of 51.30% to 70.02% during the whole growth period. The SPAD value of I. indigotica in the seedling stage was higher than that of soybean, and the intercropping mode had a significant effect on the SPAD value of I. indigotica in the seedling stage, but water deficit conditions could reduce the SPAD value of I. indigotica. In the leaf vegetative growth stage, the SPAD value rapidly increased in each treatment. At this time, the SPAD value of I. indigotica was mainly affected by water factors, and the influence degree of SPAD value under different water gradients was consistent, and the planting mode had less effect on the numerical change. In the fibrous root growth stage, the SPAD value of each treatment further increased. In the same planting mode, the water factor had a significant effect on the SPAD value (P<0.05). The higher the SPAD value, the more effectively the plant could absorb light energy, thereby increasing the potential rate of photosynthesis. There was usually a positive correlation between the chlorophyll content SPAD and the net photosynthetic rate. In the fibrous root maturation stage, the SPAD value of I. indigotica decreased, and the effect of water deficit conditions on the SPAD value of I. indigotica was more significant than that of the planting mode (P<0.05). The SPAD value change graph of I. indigotica in each growth period is shown in Figure 2. Figure 3 e).

[0144] 4. Influence on crop biomass and quality

[0145] 4.1 Influence on the biomass of I. indigotica

[0146] From Table 2, it can be concluded that the 1:1 intercropping mode is weaker in terms of stress resistance in terms of plant height. The intervention of soybean inhibits the root length of isatis, but under water stress conditions, the root length of isatis shows better resistance, and the growth is better than that of irrigation, with significant difference (P<0.05).

[0147] Table 2 Biomass and constituent elements of isatis under different treatments

[0148]

[0149] When the soil moisture is sufficient, the main root will continue to grow downward, and at the same time stimulate the development of more lateral roots. When the soil moisture is insufficient, the plant will adjust its root structure, and more lateral roots are needed to absorb limited water from the soil surface. Under the intercropping mode, the competition for water in the same plough soil layer (0-20 cm) is intense, and isatis needs to turn to a wider range of water to ensure its own water needs, reducing the growth of main roots and increasing the number of lateral roots. This response mechanism of lateral roots helps the plant to survive in an environment with insufficient water, but the intercropping mode has a more significant effect on lateral roots.

[0150] The intercropping mode reduces the vertical growth of isatis, and the lateral growth of isatis roots is more significant, and the diameter of isatis under water deficit is greater than that under sufficient irrigation. Compared with monocropping, the intercropping mode promotes the growth of isatis diameter, and there is an interactive effect, and the effect is significant (P<0.05).

[0151] Water has a positive effect on the biomass of crops. Under the same water conditions, comparing the root fresh weight of monocropping as the control group, it is found that the water competition and nutrient competition intensity when intercropping with soybean (before the maturation period of fibrous roots) is greater than that of monocropping, and the material accumulation amount in the same growth period is less than that of monocropping; the planting density of the 1:1 intercropping mode is only second to that of soybean monocropping, and the stress and competition of isatis are greater, but the resistance of isatis is stronger. The intercropping mode reduces the material accumulation of isatis, and the reduction is significant. However, under water deficit conditions, the resistance of isatis roots under the 2:1 intercropping mode is better than that of monocropping, and the material accumulation of isatis under water stress is better than that of monocropping, indicating that under mild water deficit conditions, the intercropping mode promotes the accumulation of isatis fresh weight, and at this time, the intercropping mode can bring benefits of water saving and yield increase to isatis.

[0152] The trend of root dry index was similar to that of root fresh index. The material accumulation of Isatis indigotica in intercropping mode was less than that in monoculture, but the decrease range was reduced compared with fresh root, which greatly reduced the damage degree of biomass in the later stage. The root dry accumulation in intercropping mode was better than that in monoculture under water deficit. The dry matter rate of I. indigotica ranged from 29.99% to 39.88%, with the highest dry matter rate in 1:1 intercropping, followed by monoculture, and the lowest in 2:1 intercropping. The optimal intercropping mode should be determined by considering various index factors.

[0153] Based on single plant dry weight, plot area, and planting number, the biomass was converted. The biomass of I. indigotica in monoculture mode could reach 5293.60-6119.54 kg / hm 2 , in 1:1 intercropping mode, only 2611.90-2341.72 kg / hm 2 , and in 2:1 intercropping mode, 3632.59-3814.04 kg / hm 2 .

[0154] 4.2 Effect on the content of effective components of I. indigotica

[0155] Table 3 Quality content of I. indigotica in each treatment

[0156]

[0157] Table 3 shows that the indigo content of I. indigotica ranged from 4.58 to 5.97 mg, and the intercropping mode improved the indigo content of I. indigotica, but there was a gap in the indigo content under water gradient. The indigo content ranged from 8.88 to 9.88 mg / kg. Compared with monoculture, M4W2 treatment increased by 8.18% compared with M1W2 treatment, M3W2 treatment increased by 9.06% compared with M1W2 treatment, M4W1 treatment increased by 9.92% compared with M1W1 treatment, and M3W1 treatment increased by 2.37% compared with M1W1 treatment. The range of indigo in monoculture was 8.88-9.06 mg / kg, the range of indigo in 1:1 intercropping was 9.09-9.88 mg / kg, and the range of indigo in 2:1 intercropping was 9.76-9.80 mg / kg. The fluctuation range of indigo content in 2:1 intercropping mode was the smallest, and the effect of water gradient was smaller, but the indigo in 1:1 intercropping mode showed a large fluctuation in water gradient, and the indigo content in monoculture mode was more stable.

[0158] The (R,S)-Gouyichun content showed the smallest variation range, generally between 0.2107 and 0.2510 mg / g. The variation pattern was more influenced by the intercropping pattern: the M4W2 treatment increased by 13.75% compared to the M1W2 treatment, the M3W2 treatment increased by 9.21% compared to the M1W2 treatment, the M4W1 treatment increased by 14.40% compared to the M1W1 treatment, and the M3W1 treatment increased by 4.75% compared to the M1W1 treatment. Under the same planting pattern, the M2W1 treatment decreased by 4.53% compared to the M2W2 treatment, the M3W1 treatment decreased by 8.44% compared to the M3W2 treatment, and the M4W1 treatment decreased by 3.98% compared to the M4W2 treatment. The changes in the water gradient were not significant (P>0.05).

[0159] 4.3 Effects of Interactions on Isatis indigotica Quality

[0160] Table 4 shows that both irrigation and intercropping patterns significantly affected the indigo and indirubin contents of Isatis tinctoria, reaching highly significant levels (P < 0.01). However, irrigation had no significant effect on (R,S)-goichun, while the interaction had no significant difference in indirubin, indigo, or (R,S)-goichun contents (P > 0.05). The (R,S)-goichun content only differed between planting patterns (P < 0.05). Irrigation level, intercropping pattern, and their interaction effects can significantly improve the quality of Isatis tinctoria.

[0161] Table 4 Results of Two-Way ANOVA for Soybean Quality Indicators

[0162]

[0163] Note: In the table, * indicates that the P < 0.05 level was reached; ** indicates that the P < 0.01 level was reached; ns indicates no significant difference, and the same applies below.

[0164] 5. Impact on crop water conservation and economic benefits

[0165] 5.1 Stage water consumption modulus and total water consumption

[0166] From Table 5, it can be seen that in the seedling stage, the effect of water on water consumption modulus was not significant (P>0.05), but the effect of intercropping mode reached a significant level (P<0.05). The water consumption modulus of Isatis indigotica was the largest in the leaf nutrient growth stage, reaching more than 40% of the whole growth period, and water, intercropping mode and interaction all had a very significant effect on the water consumption modulus (P<0.01). For monoculture, the water consumption modulus in the fibrous root maturation stage was the second, which could be close to 30% of the total water consumption in the whole growth period; but in the intercropping mode, the water consumption modulus in the fibrous root growth stage occupied the second highest position in the whole growth water consumption, mainly because in the intercropping mode, soybean was in the grain filling and podding stage at this time, and the growth activity was also more vigorous, and the demand for water was higher. At this time, water and intercropping mode had no significant difference (P>0.05).

[0167] Table 5 Water consumption modulus and total water consumption of Isatis indigotica and soybean in each growth stage

[0168]

[0169] Note: In the table, the small letters marked after the same column of numbers represent the significant difference of Isatis indigotica, and the capital letters represent the significant difference of soybean, and the letters in () represent the significance between treatments. The water consumption in the intercropping treatment is allocated according to the planting proportion; the same below.

[0170] The change trend of total water consumption was: M4W2>M2W2>M3W2>W1M2>M3W1>M4W1>M3W1>M1W1. Under water deficit conditions, the water consumption of Isatis indigotica was smaller than that of soybean monoculture, and lower than that of intercropping with the same water gradient, and the interaction of water, planting mode and period reached a very significant level (P<0.01). At this time, the treatment with the least water consumption was M1W1, and the total water consumption of Isatis indigotica monoculture mode in the whole growth period was only 191.53 mm, while the treatment with the least water consumption in the intercropping mode was M4W1, which was 232.79 mm, 21.52% higher than the water consumption of monoculture. Because two crops were introduced in the intercropping mode, the water consumption increased, so the benefits of intercropping and monoculture should be considered comprehensively to select the best water-saving mode.

[0171] 5.2 Water use efficiency, irrigation water use efficiency

[0172] Table 6 Water use efficiency and irrigation water use efficiency of Isatis indigotica and soybean in each treatment

[0173]

[0174] Note: In the table, the small letters marked after the same column of numbers represent the significant difference of Isatis indigotica, and the capital letters represent the significant difference of soybean, and the irrigation water in the intercropping treatment is allocated according to the planting proportion, the same below.

[0175] Water use efficiency, irrigation water use efficiency is shown in Table 6. The water use efficiency of M1W1 treatment is the highest, the water use efficiency reaches the maximum value of 27.67 kg / (hm 2 ·mm); M2W2 treatment water use efficiency is the lowest, only 8.41 kg / (hm 2 ·mm), M1W1 treatment is 2.29 times higher than M2W2 treatment.

[0176] In the same planting mode, the water use efficiency of Isatis indigotica under water deficit is higher than that of sufficient irrigation, and the water use efficiency of single soybean is the lowest, only 8.41-11.50 kg / (hm 2 ·mm), the intercropping mode improves the water use efficiency of soybean, but compared with Isatis indigotica, it cannot play a positive role in promoting, and reducing irrigation water can increase the water use efficiency of soybean.

[0177] The irrigation water use efficiency of M1W1 is the highest, reaching 71.17 kg / (hm 2 ·mm), and the utilization rate of M2W2 treatment is the lowest, only 10.57 kg / (hm 2 ·mm) during the whole growth period, and the difference in water use efficiency caused by water change has a significant effect (P<0.05). The water use efficiency of M4W1 and M3W1 intercropping modes under light water deficit is 69.99% and 64.45%, respectively. Compared with sufficient irrigation level, the water use efficiency of 2:1 intercropping mode is improved by 95.72%, and the water use efficiency of 1:1 intercropping mode is improved by 75.76%, but it cannot reach 71.17 kg / (hm 2 ·mm) which is the water use efficiency of single Isatis indigotica under light water deficit. Overall, the water use efficiency under light water deficit is better than that under sufficient irrigation. Under the premise of little difference in yield, light water deficit can effectively save irrigation water and play the potential of water saving and yield increase.

[0178] 5.3 Intercropping benefit

[0179] As shown in Table 7, the water equivalent ratio of each treatment in Isatis indigotica‖ soybean intercropping mode is >1, indicating that the water use of this intercropping mode is better than that of single cropping; the specific performance is: in the intercropping mode, there is an interaction effect between water and intercropping mode, and water has a significant effect on the water use efficiency of Isatis indigotica and soybean (P<0.05), and the planting mode and the interaction effect have a very significant effect (P<0.01). Although the total water consumption is higher than that of single Isatis indigotica, the increased water consumption promotes the increase of single plant dry weight and quality of Isatis indigotica, and plays a role in water saving, stable yield and quality improvement.

[0180] The land equivalent ratio was > 1 in the light water deficit mode, and had a significant effect on the yield difference of Isatis indigotica (P<0.01), but in the full irrigation level, the intercropping advantage was not only not embodied but also had a decreasing trend, indicating that the intercropping planting mode of Isatis indigotica and soybean can appropriately reduce the irrigation level of planting, play the role of stress resistance, and play the role of water saving.

[0181] And the interspecific competition of Isatis indigotica to soybean is <1, indicating that Isatis indigotica has a certain weakness in the growth process, and the planting density and planting proportion of Isatis indigotica and soybean should be reasonably considered when intercropping, so as to play the yield promotion effect of soybean while not being in an over-competitive passive situation. Isatis indigotica in the 1:1 intercropping mode under the full irrigation level shows the weakest interspecific competition, and the strong competition ability and dense planting environment of soybean are not suitable for the growth and development of Isatis indigotica.

[0182] Table 7 Intercropping benefit of Isatis indigotica and soybean

[0183]

[0184] 5.4 Economic benefit

[0185] The economic benefit mainly reflects the difference between the input and output of Isatis indigotica and soybean. According to the price information of Minle County in Gansu Province in 2023, the selling price of Isatis indigotica dry root is 8 yuan / kg, and the selling price of soybean is 5 yuan / kg. The input of production materials mainly includes labor cost, material equipment cost, water cost (measured water cost, water resource cost) and seed input required for planting. The specific production input items are shown in Table 8.

[0186] Table 8 Input cost of production materials of Isatis indigotica and soybean

[0187]

[0188] As shown in Table 9, the best economic benefit mode is Isatis indigotica monocropping under full irrigation M1W1, which can reach 37985.22 yuan / hm 2 , followed by M1W2 31584.86 yuan / hm 2 , the economic benefit of 2:1 intercropping mode is lower, but it is better than 1:1 intercropping and soybean monocropping. From the economic benefit, the light water deficit mode of Isatis indigotica monocropping is more conducive to water saving and income generation.

[0189] Table 9 Economic benefit under different planting modes

[0190]

[0191]

[0192] Example 3

[0193] 1. The effects of different Isatis indigotica || soybean patterns on crop growth characteristics

[0194] Reasonable collocation of Isatis indigotica and soybean for intercropping can make full use of light resources and improve the photosynthetic efficiency per unit area. Intercropping patterns also exist inter-specific competition under the constraint of water gradient, affecting the growth indicators of Isatis indigotica, such as plant height and biomass accumulation performance, which are not as good as monocropping. However, intercropping patterns significantly improve the productivity and sustainability of the intercropping system.

[0195] Intercropping patterns are beneficial to the growth and development of Isatis indigotica roots. Intercropping patterns under mild water deficit conditions have a positive impact on the growth of Isatis indigotica taproot diameter and length.

[0196] Sufficient soil moisture, high relative humidity, and appropriate shading can promote the growth of soybean (Isatis indigotica) crown, reducing the root-shoot ratio value; appropriate water stress can promote root growth and increase the root-shoot ratio, but excessive soil moisture will limit root activity and growth, which is the same as the research results of Cai Dexin.

[0197] Under drought conditions, plants can increase the root-shoot ratio to improve water use efficiency, but this will sacrifice the growth and biomass of the aboveground part. Reasonable regulation of the root-shoot ratio of Isatis indigotica and soybean can optimize the dry matter accumulation process and improve the biomass and quality of crops. This is consistent with the conclusion of Cai Qian

[30] The conclusion is consistent with the research on the effects of water stress on spring maize dry matter accumulation and biomass.

[0198] Intercropping patterns are beneficial to improving the productivity of Isatis indigotica and improving its growth conditions. Reasonable water gradient and planting patterns can promote the growth of Isatis indigotica and improve the sustainability of the planting system, but also affect the growth of the aboveground part of Isatis indigotica and the final biomass.

[0199] 2. The effects of different Isatis indigotica || soybean patterns on crop photosynthetic indicators

[0200] At different growth stages, the photosynthetic efficiency of Isatis indigotica under intercropping patterns is generally higher than that under monocropping. The net photosynthetic rate Pn of Isatis indigotica first increases and then decreases, with the maximum value appearing in the taproot growth period. The optimal treatment under sufficient irrigation conditions is M4W2, and the optimal treatment under water deficit conditions is M4W1. Intercropping improves the net photosynthetic rate of Isatis indigotica, but the net photosynthetic rate under water deficit patterns is not as good as that under monocropping patterns. At the seedling stage and leaf nutrient growth period, the net photosynthetic rate Pn of Isatis indigotica under intercropping patterns is significantly higher than that under monocropping, which indicates that intercropping patterns can provide better photosynthetic conditions in the early growth stage of crops.

[0201] The water gradient has a significant effect on the photosynthetic characteristics of crops. When the water is fully irrigated, the stomatal conductance Gs and transpiration rate Tr of crops are generally higher, and the stomatal opening of crop leaves increases, which is conducive to the absorption of CO2 and the evaporation of water, consistent with the results of Wang Chunyan

[31] Under mild water deficit, the stomatal conductance and transpiration rate of crops decrease, which is the result of the adjustment of physiological mechanisms by crops to reduce water loss.

[0202] The change in intercellular CO2 concentration Ci reflects the adjustment of photosynthetic efficiency under different water and planting modes. The regularity of Ci value is negatively correlated with the change in net photosynthetic rate Pn and stomatal conductance Gs value. Under sufficient light conditions, the higher the net photosynthetic rate Pn, the lower the intercellular CO2 concentration Ci. The Ci value of Isatis indigotica is highest at the seedling stage and lowest during the fibrous root growth period, during which the stomatal conductance Gs value and net photosynthetic rate Pn are also at a relatively high level, which together improve the photosynthetic efficiency. Water deficit increases the Ci value in intercropping mode, but has less effect on the Ci value in monocropping mode, and the Ci value under full irrigation is lower than that in monocropping. There is a significant difference in Ci concentration between I. indigotica and Glycine max under different treatments, which is related to the changes in crop physiological characteristics and growth environment, and the intercropping and mild water deficit stimulate the competitiveness of crops for water.

[0203] Intercropping and water treatment have a significant effect on the chlorophyll content of crops. The SPAD value of I. indigotica is higher than that of G. max. The SPAD value of I. indigotica is highest during the fibrous root growth period and second highest during the fibrous root maturation period. The SPAD value in intercropping mode is slightly higher than that in monocropping mode, and the content changes more stably. After I. indigotica enters the fibrous root maturation period, the net photosynthetic rate Pn, stomatal conductance Gs, and transpiration rate Tr decrease, while the intercellular CO2 concentration Ci increases slightly. The increase in chlorophyll content in the leaves compensates for the constraints caused by weak active accumulated temperature due to climate, enabling it to effectively accumulate dry matter during the fibrous root maturation period. The maturation period of G. max is earlier than that of I. indigotica, and after G. max is harvested, it can provide more land resources for I. indigotica during the fibrous root maturation period to accumulate dry matter compared to monocropping. In intercropping mode, especially under full irrigation, the SPAD value of G. max under each treatment is higher than that in monocropping. The change trend is similar to that of Zhao Changjiang et al

[32] The results of the photosynthetic physiological characteristics of G. max in the intercropping of I. indigotica || G. max are consistent with those of Wang Mingze

[33] This also suggests that intercropping mode may promote photosynthesis of crops by increasing chlorophyll content.

[0204] 3、Different I. indigotica || G. max modes have different effects on crop quality and water productivity

[0205] The plant height of I. tinctoria was the highest in M4W1 and the lowest in M1W2, the root length was the best in M4W1 and the shortest in M3W2, the lateral root number and root diameter were the best in M4W1, and the dry root weight was only inferior to M1W1, which was also under light water deficit. Under full irrigation, I. tinctoria under intercropping mode showed higher biomass per plant, which was attributed to higher photosynthetic efficiency and nutrient utilization. Meanwhile, I. tinctoria under intercropping mode showed stronger stress resistance under water deficit.

[0206] The quality of I. tinctoria was affected by intercropping mode and water gradient. Indigo was significantly affected by water and intercropping mode, indigo natural red was also affected by their interaction, but (R,S)-adivincine content only had significant difference under intercropping mode, and the quality of M4W1 was better than that of M1W1 under light water deficit. The content of effective components such as indigo, indigo natural red and (RS)-adivincine was significantly improved under intercropping mode, which was related to the interaction between plants.

[0207] Intercropping mode improved the biomass and quality of I. tinctoria. Under insufficient irrigation, optimizing intercropping mode and water gradient could realize more efficient crop production and improve the quality of crops, which was consistent with the research results of Tan Chunyan

[34] . The interaction between intercropping mode and light water deficit mode promoted the improvement of biomass and quality of I. tinctoria, but further research and discussion were needed in the later repeated verification test.

[0208] Different intercropping modes and water gradients had significant effects on water consumption modulus. In the leaf nutrient growth period, water consumption modulus accounted for more than 40% of the whole growth period, indicating that the demand for water was the most urgent at this stage. The growth period of soybean was short, but the water consumption of soybean was slightly higher than that of I. tinctoria. In intercropping mode, most of the water consumption was in the leaf nutrient growth period of I. tinctoria (branching period and flowering period of soybean), and intercropping mode improved the water consumption of the group, which was the reason for the difference in irrigation water use efficiency (P<0.05).

[0209] The results of water use efficiency showed that the water use efficiency of I. tinctoria under light water deficit was the highest among all treatments, which reflected the potential of water-saving planting to improve water use efficiency of crops.

[0210] The water use efficiency of I. tinctoria under intercropping mode was the highest, but intercropping mode improved the water use efficiency of the whole treatment, and the water use efficiency of M4W1 intercropping was the highest, followed by M3W1, and the irrigation water use efficiency of M4W1 was only inferior to M1W1.

[0211] Isatis indigotica monoculture yields the highest economic returns under mild water deficit conditions. Intercropping with soybeans reduces returns by 39.30% under full irrigation and by 21.88% under mild water deficit conditions. The main reason is the low price of soybeans; under intercropping, soybean biomass contributes less to overall returns. Furthermore, [the text abruptly shifts to a different topic]...Cao Manjun

[35] The findings of intercropping soybeans are similar. Although the intercropping pattern increases the overall water consumption, it correspondingly improves the dry weight and quality of individual Isatis indigotica plants, demonstrating the effect of water conservation, stable yield, and quality improvement. After reaching a certain planting scale, it will generate income through intercropping. However, before that, it is necessary to conduct sufficient experiments and demonstrations on the water use indicators of Isatis indigotica and soybeans under the intercropping pattern, as well as the cost and feasibility of large-scale promotion of drip irrigation under film.

[0212] Intercropping exhibits significantly higher water use efficiency under mild water deficit conditions compared to fully irrigated conditions. A moderate water deficit helps conserve irrigation water while maintaining or improving biomass and quality. The water equivalent ratio of all intercropping patterns is greater than 1, indicating that intercropping is more efficient in water use than monoculture. The land equivalent ratio results show that intercropping under mild water deficit conditions has an advantage in land use efficiency. The interspecific competitiveness of Isatis indigotica against soybean is less than 1, requiring careful adjustment of planting density and ratio in actual cultivation to maximize the benefits of intercropping. Intercropping demonstrates significant potential for water conservation and improved economic efficiency, enabling efficient and sustainable crop production.

[0213] This invention investigates the potential of water stress and intercropping patterns on water-saving, yield-stabilizing, and quality-improving effects of Isatis indigotica and soybean through a field experiment conducted at the Yimin Irrigation Experimental Station in Minle County, Zhangye City, Gansu Province. The study primarily discusses the changes in photosynthetic indicators throughout the entire growth period of Isatis indigotica, the impact of intercropping patterns on its quality, biomass, and its constituent elements, and compares the water consumption modulus and water use efficiency of Isatis indigotica under different intercropping patterns throughout its growth period. Combined with land equivalent ratio and interspecific competitiveness indicators, the degree of influence of intercropping patterns on the photosynthetic characteristics and biomass quality of Isatis indigotica is preliminarily determined. Specific research results are as follows:

[0214] (1) Intercropping promoted the growth of plant height, root length, and root diameter in Isatis indigotica, and was beneficial to the growth and development of its roots. Intercropping enhanced the photosynthetic characteristics of Isatis indigotica; under sufficient irrigation, the net photosynthetic rate (Pn) under intercropping was significantly higher than that under monoculture. Intercropping effectively mitigated the decline in stomatal conductance (Gs) and transpiration rate (Tr), which is beneficial for the crop to maintain high water use efficiency under water stress.

[0215] (2) In terms of biomass and quality, the intercropping mode improves the biomass of Isatis indigotica, improves the content of effective components of Isatis indigotica, and the crop quality is better. The intercropping mode improves the economic output of crops while also enhancing the market competitiveness of Isatis indigotica.

[0216] (3) The water-saving benefit analysis shows that under the condition of light water deficit, the intercropping mode realizes the effect of water-saving, stable yield and quality improvement by optimizing water use efficiency and irrigation water use efficiency. This provides an effective strategy for agricultural water resource management in the cold and cool irrigation area of Hexi. The economic benefit evaluation results reveal that Isatis indigotica monoculture has higher economic benefits under the condition of light water deficit, while the intercropping mode increases water consumption, but correspondingly improves the single plant dry weight and quality of Isatis indigotica, showing the economic benefits of water-saving, stable yield and quality improvement.

[0217] (4) Considering the actual water resources in the local area, the insufficient irrigation form is the main mode of crop planting irrigation, and when large areas are planted, it cannot be guaranteed that Isatis indigotica can be fully irrigated throughout the whole growth period, and it is necessary to use limited water to improve the biomass and quality of Isatis indigotica as much as possible and promote the income, that is, under the condition of light water deficit, the 2:1 intercropping planting mode can play the advantages of legume intercropping and improve the quality of Isatis indigotica, at this time, the water use efficiency and irrigation water use efficiency are better, which plays a role in water-saving, stable yield and quality improvement, and is the optimal planting mode of Isatis indigotica and soybean intercropping planting mode. It is more in line with the local planting expectations.

[0218] The above is only a preferred embodiment of the present application, and is not intended to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An efficient irrigation planting method of isatis indigotica and soybean intercropping, characterized by, Comprising the following steps: Step one, select test site The field experiment was conducted in the period of May to October in the Hongshuihe Management Station of Yimin Irrigation Experiment Station, Minle County, Zhangye City, Gansu Province, which is a representative basic irrigation experiment center in the northwest cold and arid region. The test area has good water and fertilizer retention properties. The field water holding capacity of the test soil is 24%, the pH value is about 7.2, and the soil is medium loam with a soil bulk density of 1.46 g·cm -3 . The groundwater depth is more than 20 m, there is no salinization phenomenon, and the plough layer is 0-60 cm. The Hongshuihe Management Station of Yimin Irrigation Experiment Station has a weather monitoring station, which can directly obtain rainfall, air temperature, atmospheric relative humidity and surface temperature data. Step two, test design The test is a two-factor test, a total of 8 treatments, soil moisture is set in two gradients, respectively W1 and W2, W1 is the soil moisture content of 55% to 65% of the field capacity, W2 is the soil moisture content of 70% to 80% of the field capacity; intercropping mode is single planting isatis, single planting soybean, isatis 6 rows of soybean 6 rows, isatis 12 rows of soybean 6 rows, respectively, M1, M2, M3, M4; the test has 8 treatments, 3 groups of repeats, a total of 24 plots; the soil moisture control depth of film mulching drip irrigation is 60 cm; Step three, determination of indicators and analysis; including biological characteristics index, photosynthetic index, soil moisture content, water use efficiency and intercropping benefit; the soil moisture content includes: respectively before sowing, after film sowing, before irrigation, before and after rainfall, with the depth of 100cm soil drill, hierarchical soil, excluding the surface soil, each time taking 20cm; using drying method to determine the soil moisture content; every 7-10 days, take the soil to measure, ensure that the water gradient in time adjustment; the determination range is 0-100cm; indigo root system is deep, compared with indigo, soybean root system is shallow, the plan of the range of 0-60cm, take the average value of soil moisture content in 0-60cm soil layer as the soil irrigation amount, before the branch period of soybean, because the crop root system is shallow, the soil layer plan of the range of 0-40cm; when the soil moisture content of the soil layer is lower than the lower limit of each water gradient, then irrigation is carried out, the irrigation amount is to supplement the soil moisture content to the upper limit of the soil moisture content of the plot; the precision of water metering test plot is 0.0001m 3 The irrigation amount of water metering test plot is calculated by the formula: W = 10γH p (θ i -θ j ) In the formula, W is irrigation amount, mm; γ is soil bulk density, g-cm -3 ; H p is planned tillage wet layer depth, cm; θ i is upper limit of soil control water content, %; θ j is measured soil mass water content before irrigation, %; Through the above test, it can be concluded that under the condition of mild water deficit, the 2:1 intercropping planting mode can play the advantages of intercropping with legumes, improve the quality of isatis, and has better water use efficiency and irrigation water use efficiency, which plays a role in water saving, stable yield and quality improvement. It is the optimal planting mode of isatis and soybean intercropping.

2. The efficient irrigation planting method of isatis indigotica and soybean intercropping according to claim 1, characterized in that, In step three, the biological characteristic index includes: After isatis and soybean enter the seedling stage, 3 seedlings with uniform growth and representing the average growth state of the plot are randomly selected in each plot, and the height from the base to the growth point of the plant is measured at the end of the respective growth period with a steel tape with an accuracy of 1 mm. The stem diameter at the junction of the aboveground and underground parts is measured with an electronic vernier caliper, and the average number of leaves of 3 plants is recorded as the value at that growth stage. At the end of each growth period of isatis, 3 plants with uniform growth and good representation in the plot are randomly selected by destructive sampling method, and the biological indexes of the aboveground leaves and underground roots of isatis are measured. The leaf area of isatis is measured by rectangular method, and the fresh samples are placed in a 105℃ ventilated drying oven for killing and drying until constant weight. The mass of each part of the sample is recorded; the roots of isatis and soybean are washed and dried to measure the fresh weight. Leaf area index (LAI) is the ratio of total leaf area per unit ground area to that area, which is a dimensionless index, and the mathematical expression is: LAI = total leaf area / ground area 3 plants with uniform growth of isatis or soybean are selected in each plot, and 3 plants of each crop are selected in intercropping plots. The fleshy roots of isatis need to be completely dug out to measure root length, root diameter, root weight, lateral root number, plant height, and leaf weight. The average value is taken, and finally the yield per hectare of isatis is converted according to the planting area and actual planting number of the plot.

3. The efficient irrigation planting method of isatis indigotica and soybean intercropping according to claim 1, characterized in that, In step three, the photosynthetic index includes: During the growth period of isatis, typical days with clear weather and less cloud cover are selected, and the stomatal conductance Gs, net photosynthetic rate Pn, transpiration rate Tr, and intercellular carbon dioxide concentration Ci of isatis leaves are measured by LI-6400 portable photosynthetic instrument from 9:00 to 11:00 am. 3 plants with uniform growth are randomly selected in each plot, and the middle-sized leaves without obvious damage, disease and insect pests, and similar in shape and leaf age, which can represent the average physiological state of the whole plant, are measured in vivo to avoid the water supply shortage after the leaves are detached from the plant, which leads to the weakening of cell activity and affects photosynthesis. The SPAD portable photosynthetic instrument was used to determine the chlorophyll content of leaf of I. indigotica and soybean at each growth stage. Nine plants were randomly selected in each plot, and three green leaves were randomly measured for each plant. The selection principle of leaves was consistent with the selection idea of Li-6400 leaf photosynthesis.

4. The efficient irrigation planting method of isatis indigotica and soybean intercropping according to claim 1, characterized in that, In step three, the water use efficiency includes: (1) Water consumption The water consumption of I. indigotica or soybean during the growth period was calculated by water balance method: ET = (W0 - W f ) + P + K + M - C wherein: ET is the water consumption of Isatis indigotica or Glycine max, mm; W0 is the planned water storage of the wet layer at the beginning of the growth period, mm; W f W is the planned water storage of the wet layer at the end of the growth period, mm; P is the effective precipitation during the growth period of the crop, mm, P > 5 mm; M is the irrigation amount, mm; K is the deep soil water recharge, mm; and C is the deep soil water leakage, mm. The groundwater depth of Yimin Irrigation Experimental Station is greater than 20 m, and the groundwater recharge is 0, so K = 0; the designed irrigation water is lower than the field water capacity, and no deep percolation will occur, so C = 0; Water consumption intensity (mm / d) = water consumption / growth period Water consumption modulus (%) = stage water consumption / total water consumption during the growth period (2) Water use efficiency Water use efficiency WUE (kg / hm 2 · mm -1 ) is calculated by the following formula: WUE = Y / ET In the formula, Y refers to the yield of Isatis indigotica or soybean, kg / hm 2 ET is the water consumption during the whole growth period of I. indigotica or soybean, mm Irrigation water use efficiency, IWUE (kg / hm 2 · mm -1 ) is calculated as: IWUE = Y / I where: Y is the isatis or soybean yield, kg / hm 2 ; I is the isatis or soybean irrigation amount, mm.

5. The efficient irrigation planting method of isatis indigotica and soybean intercropping according to claim 1, characterized in that, In step three, the intercropping benefit includes: (1) Land equivalent ratio The land equivalent ratio LER refers to the single-crop land area required to produce the same yield as the intercropped two or more crops in unit area, which is used to measure whether intercropping has yield advantage: LER = (Y iw / Y sw ) + (Y is / Y ss ) where: Y iw is the yield of crop A in the intercropping, kg / hm 2 ; Y is is the yield of crop B in the intercropping, kg / hm 2 ; Y sw is the yield of crop A in the monocropping, kg / hm 2 ; Y ss is the yield of crop B in the monocropping, kg / hm 2 ; LER > 1 indicates that intercropping is advantageous, and LER < 1 indicates that intercropping is disadvantaged. (2) Water equivalent ratio In field trials, the water equivalent ratio WER reflects the crop yield that can be obtained per unit of water input, and measures whether intercropping has water advantage than monocropping: WER = (WUE iw / WUE sw )+(WUE is / WUE ss ) WUE iw is the water use efficiency of the intercropped crop A, kg / (hm 2 ·mm); WUE is is the water use efficiency of the yield of the intercropped crop B, kg / (hm 2 ·mm); WUE sw is the water use efficiency of the monocropped crop A, kg / (hm 2 ·mm); WUE ss is the water use efficiency of the monocropped crop B, kg / (hm 2 ·mm); similarly, when WER>1 indicates that the intercropping has a water advantage, when WER<1 indicates that the intercropping has a water disadvantage; (3) Interspecific competition The interspecific competition of crops represents the relative competition ability of one crop relative to another, and its calculation formula is: Ag = Y iw / (Y sw × P w ) - Y is / (Y ss × P s ) wherein: Ag is the resource competitiveness of crop A relative to crop B; Y iw is the yield of crop A on the total intercropped area, kg / hm 2 ; Y is is the yield of crop B on the total intercropped area, kg / hm 2 ; Y sw is the yield of crop A in monoculture, kg / hm 2 ; Y ss is the yield of crop B in monoculture, kg / hm 2 ; P w is the proportion of crop A in intercropping, P s represents the proportion of crop B in intercropping; when Ag > 0, it indicates that crop A is more competitive than crop B, and when Ag < 0, it indicates that crop A is less competitive than crop B; (4) Economic benefit After intercropping of I. indigotica and soybean, the total input per mu of land will inevitably increase, but whether the intercropping mode can realize cost reduction and benefit increase compared with single planting mode can be calculated according to the following formula: W 效益 = W 产出 - W 投入 W 投入 = T 人工 + T 机械 + T 肥料 + T 灌溉 + T 除草 + T 农药 In the formula: W 效益 is the economic benefit cost of crops per unit area, yuan; W 产出 is the economic output cost of crops per unit area, yuan; W 投入 is the economic input cost of crops per unit area, yuan; S i is the yield of crops per unit area, kg / hm 2 ; Z i is the minimum sales price of the crop in the market, yuan / hm 2 ; T is the input cost per unit area, yuan / hm 2 .

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