A method for improving crop productivity in saline-alkali land

Abstract

The present invention belongs to the technical field of saline-alkali land cultivation, and specifically relates to a method for improving crop yield in saline-alkali land. The method measures the net photosynthetic rate of a crop as it changes with the photosynthetically active light quantum flux density gradient, uses Photosynthesis software to fit the leaf light response curve using a leaf drift model as a mathematical model, obtains the crop's light response curve, and calculates the crop's light saturation point (LSP). Using the LSP as a reference, a shade net with a shading ratio of X is used for shading, and the LSP value is used to calculate the optimal light intensity range for shading. The photosynthetically active radiation value is monitored in real time and compared with the optimal light intensity range for shading. Shading or non-shading is adopted based on the comparison result. When the measured value is within the optimal light intensity range for shading, shading is applied; if the measured value is below the optimal light intensity range for shading, no shading is applied; and when the measured value is above the optimal light intensity range for shading, a shade net with a higher shading ratio or an increased number of shade net layers is used to shade the crop. The present invention can maintain the photosynthesis of crops at a level close to the highest net photosynthetic rate of the day during the growth period, thereby improving the productivity of the crops.

Description

Technical Field

[0001] The present invention belongs to the technical field of saline-alkali land cultivation, and particularly relates to a method for improving the productivity of crops in saline-alkali land. Background Art

[0002] Crop productivity depends primarily on leaf area, net photosynthetic rate, the duration of photosynthesis, and the distribution of photosynthetic products to economically important organs. Normally, the diurnal variation in net photosynthetic rate exhibits a single peak, with lower rates in the morning and evening and higher rates at noon. However, on sunny summer days with high temperatures, low humidity, and ample sunlight, the diurnal variation in net photosynthetic rate exhibits a bimodal curve, with peaks in the morning and afternoon, and a trough at noon. This midday dip in net photosynthetic rate is known as the photosynthetic midday hiatus. The primary cause of this hiatus is stomatal restriction. Environmental factors such as light, temperature, relative humidity, and CO₂ concentration are key ecological factors that can cause partial closure of plant stomata, enhanced dark respiration, or photoinhibition of photosynthesis. Research has shown that when this phenomenon is severe, it can reduce daily photosynthetic productivity by 30%-50% or even more, hindering crop yield. At the same time, plant photosynthesis is highly sensitive to external environmental factors. Plant photosynthesis will be restricted under high temperature stress, drought stress or salt stress, causing the net photosynthetic rate to decline, the accumulation of photosynthetic products to decrease, and the distribution direction of photosynthetic products to be affected, ultimately leading to a decrease in crop yield.

[0003] Secondly, coastal saline-alkali lands have problems such as shallow and highly mineralized groundwater, high soil salinity, scarce fresh water, and poor soil tillage structure. In addition, the current forms of saline-alkali land improvement are relatively traditional and single, and the effect on soil water and salt optimization is not good. Therefore, how to provide suitable water and salt conditions for crop growth on saline-alkali land and thereby reduce or avoid photosynthetic hiatus and environmental stress to promote the improvement of crop production capacity and quality is an urgent problem that needs to be solved.

[0004] Barley is a good dual-purpose crop for both food and feed, boasting higher levels of protein, calcium, phosphorus, potassium, and vitamins A and E than other crops. However, barley cultivation in saline-alkali soils also presents the aforementioned issues of photosynthetic hiatus and environmental stress (high temperature, drought, or salt stress restricting plant photosynthesis), leading to a decrease in net photosynthetic rate. Summary of the Invention

[0005] (1) Technical issues to be resolved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a method for improving the productivity of crops in saline-alkali land. Without the use of any exogenous regulators or interfering agents, the method improves soil water and salt conditions by scientifically controlling light during the crop growth period, reduces the phenomenon of crop photosynthesis naps, alleviates environmental stress, and thus promotes crop growth and increases crop productivity. The present invention can maintain crop photosynthesis at a net photosynthetic rate close to the highest level of the day during the growth period, and has the advantages of low cost, simplicity, ease of operation, and practical application in production.

[0007] (2) Technical solution

[0008] The present invention provides a method for improving the productivity of crops in saline-alkali land, which comprises:

[0009] S1. Planting crops in saline-alkali soil. After the crop seedlings reach a height of ≥5 cm, set a photosynthetically active light quantum flux density gradient and record and measure the net photosynthetic rate of the crop at each photosynthetically active light quantum flux density.

[0010] S2. Using Photosynthesis software, the leaf drifting model was selected as the mathematical model for fitting the crop leaf light response curve. The leaf light response curve of the crop was obtained by fitting. The mathematical model expression is as follows. The initial values ​​of the model parameters are set as α = 0.01, β = 0.0001, γ = 0.005, R d =0.5;

[0011]

[0012]

[0013]

[0014] Where, P n is the net photosynthetic rate; LCP is the light compensation point; I is the photosynthetically active radiation; R d is the dark breathing efficiency; α is the initial quantum efficiency; β is the correction factor; γ = α / P nmax ; Calculate the light saturation point LSP according to the model;

[0015] S3. Based on the light saturation point LSP, calculate the light intensity range S for optimal shading. The calculation method is as follows:

[0016]

[0017] Among them, L is the light saturation point, X is the shading rate of the shade net;

[0018] S4. Control light from the time when the height of crop seedlings is ≥5cm to the time of harvest; the light control strategy is: measure the real-time photosynthetically active radiation value every day, and when the value is within the light intensity range of the optimal shading, use shade nets to shade the crops; when the value is lower than the light intensity range S for the optimal shading, do not shade the crops; when the value is higher than the light intensity range S, use shade nets with a higher shading rate or increase the number of shade net layers to shade the crops to maintain the actual light intensity received by the crops within ±8% of the light saturation point LSP.

[0019] When simulating the light response curve, calculate P n and LCP values ​​to observe the quality of the light response curve fit. In extreme weather conditions, the measured photosynthetically active radiation value may still exceed the LSP value measured by S3 even after shading with a shade net. Therefore, it is necessary to use a shade net with a higher shading rate or increase the number of shade net layers to reduce the actual light intensity received by the crop. This will isolate light that may cause photoinhibition of crop growth, photosynthetic hiatus, and high temperature and drought, thereby achieving a light control effect.

[0020] Among them, the real-time photosynthetic active radiation value of the day can be measured using a handheld photosynthetic active radiometer (SM206E-PAR, China).

[0021] According to a preferred embodiment of the present invention, in S1, a portable photosynthetic instrument is used to measure the light response curve of crop leaves; during the measurement, an open gas system is used, the gas flow rate is 500 μmol / s, the leaf chamber temperature is controlled at 28°C, an artificial LED red and blue light source is used to provide different photosynthetic active radiation PAR, and an automatic light-curve curve measurement function is used to set the photosynthetic active photon flux density (PPFD) gradient to 2000, 1800, 1600, 1400, 1200, 1000, 800, 600, 400, 200, 150, 100, 50, 30, and 0 μmol photons / (m 2 ·s); before measurement, 1300 μmol photons / (m 2 The leaves were induced with photosynthetically active radiation PAR of 100 nm for 20-30 min, the measurement time of each photosynthetically active light quantum flux density was set to 3-4 min, and the instrument automatically recorded the net photosynthetic rate.

[0022] According to a preferred embodiment of the present invention, in S1, the crop is barley; when the barley seedlings grow to a height of 5-7 cm, the measurement is performed between 09:00 and 11:00 on a clear day. During the measurement, a Li-6400 portable photosynthetic meter (Li-Cor, Inc., USA) produced by Beijing Ligaotai Co., Ltd. can be used to measure the light response curve of the barley leaves; and the artificial LED red and blue light source is preferably a Li-6400-02BLED 3 cm × 2 cm (LED light emitting surface area) red and blue light source.

[0023] According to a preferred embodiment of the present invention, in S1, the barley is spring-sown barley, planted in coastal saline-alkali land in North China, planted in early March, sown in rows, with a row spacing of 15-20 cm, a sowing depth of 3-5 cm, and a sowing rate of 140-160 kg / hm2. 2 (Preferably 150 kg / hm 2 Before sowing, combine land preparation to carry out shallow fertilization at a depth of 0-20 cm, and apply diammonium phosphate as base fertilizer at a rate of 450-750 kg / hm2. 2 The harvest time for silage barley is in early June, and the harvest time for barley grains is in mid-to-late June. The growing period is about 90-120 days.

[0024] According to a preferred embodiment of the present invention, in S1, the shallow groundwater in the saline-alkali land is buried at a depth of 1.0-10.0 m, and is salt water or brackish water mainly composed of NaCl; the soil type is desalinated fluvo-aquic soil, the texture is mainly loam, and the salinity level is 1‰-3‰.

[0025] According to a preferred embodiment of the present invention, in S4, when using a shade net to shade the planted crops, support columns are buried around the saline-alkali land, the top shade net is fixed at a height of 1.56-1.65m from the ground, and side shade nets are fixed on all four sides of the saline-alkali land.

[0026] According to a preferred embodiment of the present invention, in S3, the shading rate X of the shading net is 30-50%, preferably 30%, 35%, or 40%.

[0027] The present invention limits the crop emergence height in S1 to ≥5cm primarily to improve the crop's tolerance during the determination of the leaf light response curve, avoiding seedling burn caused by excessively high photosynthetically active light quantum flux density during the test, and the adverse effects of significant light shading on crop growth during the seedling stage. Therefore, light control treatment is performed after the crop's growth stabilizes. Furthermore, the LSP value measured for crops with an emergence height ≥5cm is more valuable as a reference value for subsequent light control strategies, which can more effectively increase crop yields.

[0028] It should be noted that even for the same crop, the results of the light response curve fitting will be different due to differences in the soil conditions, climatic conditions, crop growth period, etc. of the planting area, and the calculated light saturation point LSP will also be different. Therefore, in actual production applications, the light response curve should be measured each time and the light saturation point LSP should be calculated. Using the light saturation point LSP as a reference, the optimal shading light intensity range for the crop in the plot is calculated, and the light control strategy is determined using the optimal shading light intensity range. Although the LSP may fluctuate and change slightly with different crop growth stages, the LSP calculated based on the on-site measured values ​​can be closer to the actual LSP value of the crop at each stage of the planting plot.

[0029] (3) Beneficial effects

[0030] The present invention uses Photosynthesis software to select a leaf drift model as a crop leaf light response curve fitting mathematical model based on measured barley photosynthesis parameters of crops grown in saline-alkali land at different photosynthetic active light quantum flux densities, and obtains a crop leaf light response curve by fitting. The crop light saturation point is calculated based on the model, and a light control strategy is designed based on the light saturation point. A shade net is used to control the light intensity received by the crop to be close to the light saturation point, thereby artificially taking shading measures to isolate the light intensity above the light saturation point, thereby avoiding the photoinhibition of crop growth caused by this part of the light intensity. At the same time, the light control strategy can reduce the amount of solar radiation reaching the ground, thereby improving the microclimate for crop growth, avoiding the occurrence of high temperature and drought, reducing air temperature and soil temperature, reducing the transpiration rate, weakening the evaporation of surface soil water, increasing soil moisture, reducing the rate at which soluble salt in the soil evaporates to the soil surface along with soil water, thereby increasing soil water content and reducing soil salt content, alleviating crop drought stress and salt stress, and providing good water and salt conditions for the growth of crops in saline-alkali land. Secondly, the light control strategy can reduce the temperature of plant leaves, increase the relative humidity of the air, reduce the water vapor pressure deficit of leaves and plant transpiration, increase the stomatal aperture, and improve the water use efficiency of leaves, thereby reducing or even eliminating the phenomenon of plant photosynthetic midday nap and increasing the net photosynthetic rate of plants. The present invention adopts a reasonable light control strategy on saline-alkali land, so that the photosynthesis of crops is always maintained at a maximum net photosynthetic rate close to that of the day during the growth period, reducing the phenomenon of light inhibition, alleviating the impact of environmental stress and crop photosynthetic midday nap on crop production capacity, and improving crop production capacity.

[0031] By applying the scheme of the present invention to the cultivation of barley in coastal saline-alkali land, the results show that in salt ponds with salinity levels of 1‰ and 3‰, the light control strategy of the present invention can increase the soil moisture content within 1.2m of soil and reduce the soil salt content within 1.2m of soil, thereby effectively improving the soil water and salt environment; compared with the test site without light control treatment, the light control strategy of the present invention can not only significantly increase the height of barley plants, increase the tillering of barley plants, increase the leaf area and relative water content of barley leaves, and promote the growth of barley, but also increase the ear length, number of grains per ear and ear weight of barley to increase barley grain yield, increase the yield of silage barley and the crude protein content of barley grains, thereby achieving the goal of improving the nutritional value and quality of barley grains while increasing barley yield.

[0032] Therefore, the present invention provides a cultivation technology for improving the productivity and quality of barley in saline-alkali land. On the one hand, barley is used to improve the soil structure of coastal saline-alkali land, increase surface cover, absorb salt ions, reduce soil pH and total salt content, improve saline-alkali soil, and optimize land resources. On the other hand, low-quality land resources are used to provide high-quality feed raw materials such as silage and grains. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is the light response curve of barley in Example 1.

[0034] Figure 2 To grow barley in salt ponds with salinity levels of 1‰ and 3‰, the soil water content and salinity at depths of 0-20cm, 20-40cm, 40-60cm, 60-80cm, 80-100cm and 100-120cm were measured with and without light control during the entire growth period of barley.

[0035] Figure 3 To compare plant height, barberry number, flag leaf area, and leaf relative water content of barley grown in salt ponds with salinity levels of 1‰ and 3‰ during the entire growth period of barley with and without light control. The values ​​used in the figure are mean ± SD, and different letters between different treatments indicate significant differences, P < 0.05. DETAILED DESCRIPTION

[0036] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation methods in conjunction with the accompanying drawings.

[0037] The present invention measures the net photosynthetic rate of crops as it changes with the gradient of photosynthetically active light quantum flux density (PPFD), and uses Photosynthesis software to select a leaf drift model as the mathematical model for fitting the leaf light response curve to obtain the light response curve. The light saturation point (LSP) of the crop is calculated, and a shading net with a shading rate of X is used for shading treatment using the LSP value. The optimal shading light intensity range is calculated using the LSP value. The light intensity (photosynthetically active radiation value) of the day is monitored in real time, compared with the optimal shading light intensity range, and shading or non-shading treatment is adopted based on the comparison result. Among them, the real-time light intensity can be measured by a photosynthetic active radiometer (SM206E-PAR, China). When the measured value is within the light intensity range of the optimal shading, the crops are artificially shaded using a shade net with a shading rate of X; if the measured value is lower than the light intensity range of the optimal shading, no shading is performed; when the measured value is higher than the light intensity range of the optimal shading, a shade net with a larger shading rate or an increased number of shade net layers is used to shade the crops. Through the above-mentioned means, the actual light intensity received by the crops is maintained within ±8% of the light saturation point LSP. The present invention adopts a reasonable light control strategy on saline-alkali land, so that the photosynthesis of crops is always maintained at a net photosynthetic rate close to the highest rate of the day during the growth period, and comprehensively improves the crop productivity from four aspects: reducing light inhibition, improving the microclimate of crop growth, alleviating environmental stress and inhibiting photosynthetic midday break. At the same time, surprisingly, when the present invention is applied to barley cultivation in saline-alkali land, it not only increases the yield of barley grains and silage barley, but also improves the crude protein content of barley grains, thereby increasing the yield of barley while improving its nutritional value.

[0038] The following describes the preferred embodiments of the present invention.

[0039] Example 1

[0040] 1. Test conditions

[0041] This experiment was conducted in the salt pond of the Nanpi Ecological Agriculture Experimental Station of the Chinese Academy of Sciences. Located in Nanpi County, Cangzhou City, Hebei Province, the area has a typical warm temperate semi-humid continental monsoon climate, with an average temperature of 12.3°C and an average rainfall of 520 mm. The annual rainfall distribution is uneven. The shallow groundwater depth is 1.0-10.0 m, mainly salt water or brackish water with NaCl as the main component. The soil type is desalinated fluvo-aquic soil with a texture mainly composed of loam. The physical and chemical properties of soils with different salinity levels in the salt pond of the experimental area are shown in Table 1.

[0042] Table 1: Initial soil physical and chemical properties of the experimental area

[0043]

[0044] 2. Experimental Design

[0045] (1) The experiment was conducted from March 7 to June 26, 2023. Barley variety “Kenpiomai 13” was selected as the test crop. It was sown in rows with a row spacing of 20 cm and a sowing rate of 150 kg / hm2. 2 During land preparation, diammonium phosphate (total nutrient N-P2O5 ≥ 64.0%) was applied as base fertilizer at a rate of 750 kg / hm2. 2 The area of ​​each salt pond is 3.2m×2.0m, and the interval between adjacent salt ponds is 15cm.

[0046] (2) The photosynthetic parameters of barley under different photosynthetic active light quantum flux densities were measured, and the light response curve of barley leaves was obtained by fitting.

[0047] Specifically, after the seedlings grew to 5-7 cm, the light response curve of barley leaves was measured using a Li-6400 portable photosynthetic instrument (Li-Cor, Inc, USA) produced by Beijing Ligaotai Co., Ltd. The automatic light-curve curve measurement function was selected, and the photosynthetic active light quantum flux density (PPFD) gradient was set to 2000, 1800, 1600, 1400, 1200, 1000, 800, 600, 400, 200, 150, 100, 50, 30, and 0 μmol photons / (m 2 ·s), and before measurement, the concentration was 1300 μmol photons / (m 2 ·s) of photosynthetically active radiation PAR was induced on the leaves for 20-30 minutes, and the measurement time of each radiation intensity was set to 3-4 minutes. The mathematical model of leaf drift response curve was selected for fitting. The curve after fitting is as follows Figure 1 As shown in the figure, the light saturation point (LSP) value of barley leaves was calculated to be 1064 μmol / m 2 s. The mathematical model of leaf light response curve fitting is as follows:

[0048]

[0049]

[0050]

[0051] The initial values ​​of the model parameters are set as α = 0.01, β = 0.0001, γ = 0.005, R d =0.5; where P n is the net photosynthetic rate; LCP is the light compensation point; I is the photosynthetically active radiation; R d is the dark breathing efficiency; α is the initial quantum efficiency; β is the correction factor; γ = α / P nmax ; Calculate the light saturation point LSP based on the model.

[0052] (3) As shown in Table 1, the experiment was conducted in salt ponds with soil salinity of 1‰ and 3‰, respectively. In the salt ponds with different salinity levels, no light control and light control treatments were set up, for a total of 4 treatments, with 4 replicates for each treatment. A shade net with a shading rate of about 30% was selected. The light intensity range for the optimal shading of barley was calculated as 1418.7 μmol / m 2 ·s-1636.9μmol / m 2 ·s.

[0053]

[0054] Wherein, S is the light intensity range for optimal shading, L is the light saturation point value obtained from the measured light response curve of barley, and X is the shading rate of the shading net. In this embodiment, X=30%.

[0055] The light intensity of the shade net with a shading rate of about 30% is 1418.7 μmol / m 2 ·s-1636.9μmol / m 2 The barley plants were shaded and treated with light control to reduce the light intensity to 993.1 μmol / m 2 ·s-1145.8μmol / m 2 ·s, which is within ±8% of the light saturation point (LSP) value of barley leaves.

[0056] (4) The real-time photosynthetic active radiation value of the day was measured using a handheld photosynthetic active radiometer (SM206E-PAR, China). When the value was between 1418.7 and 1636.9 μmol / m 2 ·s range, shade the barley with a 30% shading net. When the value is lower than 1418.7-1636.9 μmol / m 2 ·s range, the shade net is removed; but its value is higher than 1418.7-1636.9μmol / m 2 ·s range, a shading net with a shading rate of 35% or 40% can be used. For example, when the light intensity is extremely high, the real-time photosynthetic active radiation value reaches 1800μmol / m 2 ·s, you can consider using a shade net with a shading rate of 40%.

[0057] The shade net is set up as follows: a steel pipe with a height of 1.6m is buried deep around each salt pond, and a double U-shaped pipe clamp is installed on the top to fix the shade net, providing shade on all four sides of the ground.

[0058] The above light control measures will be implemented throughout the entire growth cycle of barley, starting from when the seedlings emerge at 5-7 cm to harvest (March 7-June 26, 2023).

[0059] In order to compare the differences between the soil water and salt conditions and barley growth conditions in the salt pond after light control and without light control, a parallel control experiment was also set up in this example. All the planting environments of the parallel control experiment were the same as those of the light control treatment experiment. The only difference was that the parallel control experiment did not perform light control treatment, that is, the barley was in a natural light environment during the growth period from 5-7 cm emergence to harvest.

[0060] 3. Investigation

[0061] (1) Soil water and salt conditions

[0062] Four growth stages of barley were selected, namely the seedling stage (March 25), jointing stage (April 25), heading stage (May 25) and maturity stage (June 25). A homemade stainless steel soil drill was used to collect soil samples at 0-20 cm, 20-40 cm, 40-60 cm, 60-80 cm, 80-100 cm and 100-120 cm between two rows of barley in each experimental plot. The soil water content and soil salt content of 1.2 m soil under different treatments in the experimental area were investigated in a stratified manner.

[0063] (2) Barley growth status

[0064] At the milky stage of barley (June 5), plant height, tiller number (one-meter double row), flag leaf area, and leaf relative moisture content of barley plants under different treatments were investigated. Silage yield was calculated from the two-row one-meter silage barley plants. At harvest (June 26), grain yield was determined from the barley plants under different treatments. Ear length, number of grains per ear, and ear weight were also measured. Crude protein content of barley grains under different treatments was also determined.

[0065] 4. Survey Results

[0066] (1) Soil water and salt conditions

[0067] like Figure 2 As shown in Figure 2, in a salt pond with a salinity level of 1‰, compared with the parallel control experiment without light control, the light control treatment increased the soil water content of the 0-20cm, 20-40cm, 40-60cm, 60-80cm, 80-100cm and 100-120cm soil layers by an average of 20.88%, 15.81%, 12.63%, 11.36%, 6.08% and 9.73% respectively during the whole growth period of barley (see Figure 2 At the same time, the soil salinity of each soil layer decreased by 8.83%, 12.72%, 14.18%, 13.35%, 0.33% and 9.72% respectively (see Figure 2 B).

[0068] In a salt pond with a salinity level of 3‰, compared with the parallel control experiment without light control, the light control treatment increased the soil water content of 0-20cm, 20-40cm, 40-60cm, 60-80cm, 80-100cm and 100-120cm layers of barley by an average of 23.1%, 8.91%, 6.94%, 5.56%, 6.45% and 11.57% respectively during the whole growth period (see Figure 2 At the same time, the soil salinity of each soil layer decreased by 17.31%, 20.52%, 16.91%, 22.92%, 13.37% and 12.49% respectively (see Figure 2 B).

[0069] These experimental results show that light control treatment significantly increased soil water content within 1.2 m of soil depth and simultaneously reduced soil salinity within 1.2 m of soil depth in salt ponds with salinity levels of 1‰ and 3‰. This improved water-salt environment is beneficial to the growth of crops such as barley.

[0070] (2) Barley growth status

[0071] A. Barley plant height, tiller number, leaf area and leaf relative water content under different treatments Figure 3 As shown in the results, in a salt pond with a salinity level of 1‰, compared with the parallel control experiment without light control, the light control treatment increased barley plant height, tiller number, flag leaf area, and leaf relative water content by 12.00%, 17.54%, 1.71%, and 28.75%, respectively. These values ​​were significantly different from those in the non-light control treatment. In a salt pond with a salinity level of 3‰, compared with the parallel control experiment without light control, the light control treatment significantly increased barley plant height, tiller number, flag leaf area, and leaf relative water content by 13.59%, 11.14%, 36.60%, and 14.71%, respectively.

[0072] The above results show that in salt ponds with salinity levels of 1‰ and 3‰, light control treatment can significantly increase barley plant height, increase barley plant tillering, increase barley leaf area and relative water content, and promote barley growth.

[0073] B. Barley yield and quality under different treatments

[0074] As shown in Table 2, in a salt pond with a salinity level of 1‰, compared with the parallel control experiment without light control, the light control treatment significantly increased the barley ear length, number of grains per ear, and ear weight by 18.84%, 13.11%, and 8.89%, respectively, and significantly increased the barley silage yield and grain yield by 7.95% and 10.10%, respectively, and significantly increased the crude protein content of barley grains by 5.16%.

[0075] In a salt pond with a salinity level of 3‰, compared with the parallel control experiment without light control, the light control treatment significantly increased the barley ear length, number of grains per ear, and ear weight by 20%, 31.55%, and 26.76%, respectively, increased the barley silage yield and grain yield by 4.32% and 4.08%, respectively, and significantly increased the crude protein content of barley grains by 6.65%.

[0076] Table 2: Barley yield and quality under different treatments

[0077]

[0078] Note: The values ​​in the above table are mean ± standard deviation, and different letters between different treatments indicate significant differences, P < 0.05.

[0079] The above experimental and survey results show that in salt ponds with salinity levels of 1‰ and 3‰, light control treatment can increase barley grain yield by increasing barley ear length, number of grains per ear and ear weight, and light control treatment can significantly increase the yield of silage barley and improve the crude protein content of barley grains.

[0080] In summary, when the light control strategy for saline-alkali crops provided by the present invention is applied to barley, barley is planted on mild (soil salt content of 1‰) and moderate (soil salt content of 3‰) saline-alkali land. The light control strategy can significantly increase soil moisture content, reduce soil salt content, and promote the growth of barley, while increasing silage barley yield and grain yield while also increasing grain crude protein content. Therefore, the present invention can be used as an important method to improve soil water and salt conditions in mild and moderate saline-alkali land and promote barley production capacity and quality.

[0081] The present invention, without the use of any exogenous regulators or interfering agents, scientifically controls light during the growth period of crops in saline-alkali soil, thereby improving soil water and salt conditions, alleviating the phenomenon of crop photosynthesis midday naps, and alleviating environmental stress, thereby promoting crop growth and increasing crop productivity. The present invention can maintain crop photosynthesis at a near-maximum daily net photosynthetic rate throughout the growth period, offering advantages such as low cost, simplicity, ease of operation, and practical applicability.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving crop productivity in saline-alkali land, characterized in that: include: S1. Planting crops in saline-alkali soil. After the crop seedlings reach a height of ≥5 cm, set a photosynthetically active light quantum flux density gradient and record and measure the net photosynthetic rate of the crop at each photosynthetically active light quantum flux density. S2. Using Photosynthesis software, the leaf drifting model was selected as the mathematical model for fitting the crop leaf light response curve. The leaf light response curve of the crop was obtained by fitting. The mathematical model expression is as follows. The initial values ​​of the model parameters are set as α = 0.01, β = 0.0001, γ = 0.005, R d =0.5; Where, P n is the net photosynthetic rate; LCP is the light compensation point; I is the photosynthetically active radiation; R d is the dark breathing efficiency; α is the initial quantum efficiency; β is the correction factor; γ = α / P nmax ; Calculate the light saturation point LSP according to the model; S3. Based on the light saturation point LSP, calculate the light intensity range S for optimal shading. The calculation method is as follows: Wherein, LSP is the light saturation point, X is the shading rate of the shade net; the shading rate X of the shade net ranges from 30% to 50%. S4. Control light from the time when the height of crop seedlings is ≥5cm to the time of harvest; the light control strategy is: measure the real-time photosynthetically active radiation value every day, and when the value is within the light intensity range of the optimal shading, use shade nets to shade the crops; when the value is lower than the light intensity range S for the optimal shading, do not shade the crops; when the value is higher than the light intensity range S, use shade nets with a higher shading rate or increase the number of shade net layers to shade the crops to maintain the actual light intensity received by the crops within ±8% of the light saturation point LSP.

2. The method according to claim 1, characterized in that In S1, a portable photosynthetic instrument was used to measure the light response curve of crop leaves. During the measurement, an open gas system was used with a gas flow rate of 500 μmol / s, the leaf chamber temperature was controlled at 28°C, and artificial LED red and blue light sources were used to provide different photosynthetic active radiation PARs. The automatic light-curve curve measurement function was used, and the photosynthetic active light quantum flux density gradient was set to 2000, 1800, 1600, 1400, 1200, 1000, 800, 600, 400, 200, 150, 100, 50, 30, and 0 μmolphotons / (m 2 ·s); before measurement, 1300 μmolphotons / (m 2 The leaves were induced with photosynthetically active radiation PAR of 100 nm for 20-30 min, the measurement time of each photosynthetically active light quantum flux density was set to 3-4 min, and the instrument automatically recorded the net photosynthetic rate.

3. The method according to claim 1, characterized in that In S1, the crop is barley; when the barley seedlings grow to a height of 5-7 cm, the measurement is performed between 09:00 and 11:00 on a clear day.

4. The method according to claim 3, characterized in that In S1, the barley is spring-sown barley, planted in coastal saline-alkali land in North China, planted in early March, sown in rows with a row spacing of 15-20 cm, a sowing depth of 3-5 cm, and a sowing rate of 140-160 kg / hm2. 2 Before sowing, combine land preparation to apply shallow fertilizer at a depth of 0-20 cm, and use diammonium phosphate as base fertilizer at a rate of 450-750 kg / hm2. 2 .

5. The method according to claim 4, characterized in that The shallow groundwater in the saline-alkali land is buried at a depth of 1.0-10.0 m, and is salt water or brackish water mainly composed of NaCl; the soil type is desalinated fluvo-aquic soil, the texture is mainly loam, and the salinity level is 1‰-3‰.

6. The method according to claim 1, wherein In S4, when using a shade net to shade the planted crops, support columns are buried around the saline-alkali land plot, the top shade net is fixed at a height of 1.56-1.65m from the ground, and side shade nets are fixed on all four sides of the saline-alkali land plot.

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