Method for regulating and controlling rice field water environment through irrigation and nitrogen application

Abstract

The invention discloses a method for regulating and controlling the water environment of a rice field by irrigation and nitrogen application, and relates to the technical field of rice cultivation, which comprises the following steps: designing and executing field trials of an irrigation mode and a nitrogen supply mode; analyzing a concentration change rule and a loss rule of nitrogen and phosphorus in rice field water in the irrigation mode and the nitrogen supply mode to determine a response mechanism of rice field water quality to the irrigation mode and the nitrogen supply mode; obtaining the relevance between the rice water nitrogen utilization efficiency and the rice field water nitrogen and phosphorus concentration change rule and loss rule in the irrigation mode and the nitrogen supply mode; and determining a water-nitrogen coupling mode of rice production in the target area so as to realize regulation and control of the rice field water environment. By designing and implementing field trials of different irrigation modes and nitrogen supply modes, water nitrogen and phosphorus concentration change and loss rules during rice growth are analyzed, and a response mechanism of rice field water quality to irrigation and nitrogen application modes can regulate and control a rice field water environment, improve water nitrogen utilization efficiency and reduce nitrogen and phosphorus loss. And water and nutrient management in rice production is optimized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of rice cultivation, in particular to a method for regulating water environment in rice field by irrigation and nitrogen application. BACKGROUND

[0002] In the southern region of China, rainfall is frequent, water resources are abundant, agricultural development is rapid, and the intensity of fertilizer application is high. Under the influence of the rainy climate, nitrogen fertilizer is easily lost with surface runoff or underground seepage, becoming an important source of water body eutrophication. Existing research shows that the utilization rate of nitrogen fertilizer in farmland is generally low, only 30% to 35%, and a large amount of nitrogen is lost in the form of ammonia volatilization, runoff, leaching and gas emission, causing resource waste and ecological risk.

[0003] The key to affecting nitrogen loss lies in water and nutrient management. Irrigation method determines the soil water state, and then affects the mineralization of organic matter, the nitrification-denitrification process of nitrogen and the absorption efficiency of crops, and also affects the frequency and intensity of runoff and seepage. Water-saving irrigation techniques such as dry-wet alternating irrigation have been widely studied, and have the potential to regulate water and improve nitrogen utilization rate, but the research on its environmental impact is still not comprehensive.

[0004] On the other hand, the type and application method of fertilizer also significantly affect the fate of nitrogen. Conventional fertilizers have the problem of fast nitrogen release and high concentration at the initial stage of application, which increases the risk of initial runoff and volatilization. Controlled-release fertilizers can coordinate nutrient release and crop demand through slow-release mechanisms, reduce loss risk, and improve fertilizer utilization efficiency, gradually becoming the direction of popularization. At the same time, new mechanized fertilization techniques such as side deep application have also attracted attention due to their labor-saving and efficient characteristics, but the research on the nitrogen migration behavior and water quality impact is still limited. In addition, in some rice planting areas, the critical growth period of crops coincides with the rainy season, and the rainfall intensity is large and concentrated, and the surface and underground water flow is frequent, which easily causes a large amount of nitrogen to flow out in a short time. After the rain, intermittent drought occurs, which further exacerbates the contradiction between water and nutrient supply and demand.

[0005] Existing technologies mostly take conventional fertilizers and traditional irrigation as the research object, and lack of systematic research on nitrogen migration, changes in field water quality and crop yield under the joint regulation of controlled-release fertilizer combined with water-saving irrigation and other multiple factors. Especially lacking of systematic evaluation technology to study the water quality, nitrogen dynamics and loss mechanism in rice field to achieve the comprehensive goal of water saving, emission reduction, efficiency improvement and stable yield.

[0006] In view of the problems in the related art, no effective solution has been proposed so far. SUMMARY

[0007] In view of the problems in the related art, the present application proposes a method for regulating water environment in rice field by irrigation and nitrogen application to overcome the above technical problems existing in the prior art.

[0008] To this end, the specific technical solutions adopted by the present application are as follows:

[0009] A method for regulating the water environment in a rice field by irrigation and nitrogen application, the method comprising:

[0010] S1. Design and perform field tests of irrigation modes and nitrogen supply modes according to the rainfall characteristics of the target region and the growth and development stages of rice;

[0011] S2. Based on the results of the field tests, analyze the concentration variation and loss rules of water, nitrogen and phosphorus in the rice field under the irrigation modes and nitrogen supply modes, to determine the response mechanism of the water quality in the rice field to the irrigation modes and nitrogen supply modes;

[0012] S3. According to the analysis and determination results of the field tests, obtain the correlation between the water and nitrogen utilization efficiency of rice and the concentration variation and loss rules of water, nitrogen and phosphorus in the rice field under the irrigation modes and nitrogen supply modes;

[0013] S4. Based on the response mechanism of the water quality in the rice field to the irrigation modes and nitrogen supply modes, and the correlation between the water and nitrogen utilization efficiency of rice and the concentration variation and loss rules of water, nitrogen and phosphorus in the rice field, determine the water and nitrogen coupling mode for rice production in the target region, to realize the regulation of the water environment in the rice field.

[0014] Further, the irrigation mode includes: rain-based irrigation and conventional flooding irrigation.

[0015] Further, the rain-based irrigation includes:

[0016] In the target region, set up a test field, combine the rainfall characteristics of the target region, and irrigate within 20 days after the rice is transplanted to the test field, to maintain the field water depth at 5-15 mm, to promote the rice into the green-up period;

[0017] After the rice enters the green-up period, perform the first irrigation, irrigate the field water depth to 40-60 mm, then naturally dry, and according to the pre-buried underground water level observation tube, monitor the soil moisture condition and the growth of rice;

[0018] According to the monitoring results and the growth and development stages of rice, periodically irrigate according to the irrigation to the field water depth of 40-60 mm to natural dry, until the rice enters the flowering stage, and keep the field water depth at 30-50 mm for one week during the flowering stage;

[0019] 10 days before the rice is harvested, stop irrigation and perform natural dry.

[0020] Further, the rain-based irrigation also includes: adjusting the water storage depth of the rice field according to the rainfall characteristics of the target region and the growth and development stages of rice.

[0021] Further, adjusting the water storage depth of the rice field according to the rainfall characteristics of the target region and the growth and development stages of rice includes:

[0022] During the greening period of rice, if rainfall occurs, the paddy field is stored to 20mm;

[0023] During the tillering period to the jointing period of rice, if rainfall occurs, the paddy field is stored to 80mm;

[0024] During the jointing period to the maturation period of rice, if rainfall occurs, the paddy field is stored to 100mm;

[0025] In the growth and development stage of rice, if the target area rainfall exceeds the storage depth of the corresponding stage, drainage is carried out to promote the growth and development of rice.

[0026] Further, the nitrogen supply mode includes: 6 nitrogen fertilizer operation mode treatments and 1 no fertilizer treatment.

[0027] Further, the nitrogen fertilizer includes: slow control fertilization and urea.

[0028] Further, the determination includes: observation index and sample sampling.

[0029] Further, the observation index includes: the physical and chemical properties of the test field soil, the rice growth index, the rice yield and composition, the irrigation amount, the rainfall, the rice nitrogen uptake, the soil nitrogen and phosphorus content, the water output index, the water nutrient index and the field water depth.

[0030] Further, the sample sampling includes:

[0031] The test field is divided into several plots, target plots are selected and sampling points are uniformly arranged in each target plot, surface soil samples of 0-20cm depth are collected, mixed uniformly and then configured for treatment, and the physical and chemical properties of the test field soil are analyzed;

[0032] According to the growth and development period of rice, 12 rice samples are collected in each plot at each target period, and the rice growth index is determined;

[0033] Based on the maturation period of rice, 5m 2 quadrats are selected in each plot for rice yield and composition determination and rice nitrogen uptake determination;

[0034] The runoff water of each plot after rainfall is collected by using a covered overflow barrel, and the paddy field leakage water is collected by using a pre-buried iron leakage barrel, and the water output index is determined;

[0035] The ceramic head soil seepage solution collector is buried at different distances from the water inlet of each plot, and the soil leakage water is collected in the preset time period combined with irrigation and rainfall events, and the water nutrient index is determined.

[0036] The beneficial effects of the present application are:

[0037] The application discloses a method for regulating paddy field water environment by irrigation and nitrogen application, and relates to the field of water and nitrogen utilization efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained based on these drawings without creative labor.

[0039] Figure 1 is a flow chart of a method for regulating paddy field water environment by irrigation and nitrogen application according to an embodiment of the present application;

[0040] Figure 2 is a technical roadmap of a method for regulating paddy field water environment by irrigation and nitrogen application according to an embodiment of the present application;

[0041] Figure 3 is an irrigation amount schematic diagram under different irrigation modes in a method for regulating paddy field water environment by irrigation and nitrogen application according to an embodiment of the present application;

[0042] Figure 4 is a field water concentration change schematic diagram of different treatments after fertilization in a method for regulating paddy field water environment by irrigation and nitrogen application according to an embodiment of the present application;

[0043] Figure 5 is a TN runoff loss amount and seepage loss amount schematic diagram of different water and nitrogen treatments in a whole growth period of rice in a method for regulating paddy field water environment by irrigation and nitrogen application according to an embodiment of the present application;

[0044] Figure 6 is a rice plant height influence schematic diagram of different water and nitrogen treatments in a method for regulating paddy field water environment by irrigation and nitrogen application according to an embodiment of the present application;

[0045] Figure 7 is a rice leaf SPAD value influence schematic diagram of different water and nitrogen treatments in a method for regulating paddy field water environment by irrigation and nitrogen application according to an embodiment of the present application. DETAILED DESCRIPTION

[0046] To further illustrate the embodiments, the present application provides accompanying drawings which are part of the disclosure of the present application, mainly used to illustrate the embodiments, and can be explained in conjunction with the related description of the specification to understand the operating principle of the embodiments. Those skilled in the art should understand other possible implementations and advantages of the present application by referring to these contents.

[0047] According to an embodiment of the present application, a method for regulating water environment in rice field by irrigation and nitrogen application is provided.

[0048] The present application will be further described in conjunction with the accompanying drawings and specific embodiments, as shown, according to the method for regulating water environment in rice field by irrigation and nitrogen application of the embodiments of the present application, the method comprises: Figure 1

[0049] S1, according to the rainfall characteristics of the target area and the growth and development stage of rice, design and implement field test of irrigation mode and nitrogen supply mode;

[0050] S2, based on the results of field test, analyze the concentration change rule and loss rule of water, nitrogen and phosphorus in rice field under irrigation mode and nitrogen supply mode, to determine the response mechanism of rice field water quality to irrigation mode and nitrogen supply mode;

[0051] S3, according to the analysis and determination results of field test, obtain the correlation between water and nitrogen utilization efficiency of rice and the concentration change rule and loss rule of water, nitrogen and phosphorus in rice field under irrigation mode and nitrogen supply mode;

[0052] S4, combined with the response mechanism of rice field water quality to irrigation mode and nitrogen supply mode, the correlation between water and nitrogen utilization efficiency of rice and the concentration change rule and loss rule of water, nitrogen and phosphorus in rice field, determine the water and nitrogen coupling mode of rice production in the target area, to realize the regulation of water environment in rice field.

[0053] In this alternative embodiment, the irrigation mode includes: appropriate rain irrigation and conventional flooding irrigation.

[0054] In this alternative embodiment, the appropriate rain irrigation includes:

[0055] In the target area, set up test field, combined with the rainfall characteristics of the target area, irrigate within 20 days after rice is transplanted to the test field, maintain the depth of field water at 5-15mm, to promote rice into the green period;

[0056] After the rice enters the green period, carry out the first irrigation, irrigate the field water depth to 40-60mm, then dry naturally, and according to the pre-buried underground water level observation tube, monitor the soil moisture content and rice growth;

[0057] ​According to the monitoring result and the growth stage of the rice, the rice is periodically irrigated from 40-60 mm of water depth to natural dry, until the rice enters the flowering stage, and the water depth is kept at 30-50 mm during the flowering stage for one week.

[0058] Ten days before the rice is harvested, the irrigation is stopped and the natural dry is performed.

[0059] In this optional embodiment, the rain-adaptive irrigation further includes: adjusting the water storage depth of the paddy field according to the rainfall characteristics of the target area and the growth stage of the rice.

[0060] In this optional embodiment, adjusting the water storage depth of the paddy field according to the rainfall characteristics of the target area and the growth stage of the rice includes:

[0061] During the greening stage of the rice, if it rains, the water storage depth of the paddy field is 20 mm;

[0062] During the tillering stage to the jointing stage of the rice, if it rains, the water storage depth of the paddy field is 80 mm;

[0063] During the jointing stage to the maturation stage of the rice, if it rains, the water storage depth of the paddy field is 100 mm;

[0064] During the growth stage of the rice, if the rainfall of the target area exceeds the water storage depth of the corresponding stage, the water is drained to promote the growth and development of the rice.

[0065] In this optional embodiment, the nitrogen supply mode includes: 6 nitrogen fertilizer operation mode treatments and 1 no fertilizer treatment.

[0066] In this optional embodiment, the nitrogen fertilizer includes: slow-release fertilizer and urea.

[0067] In this optional embodiment, the determination includes: observation indexes and sample sampling.

[0068] In this optional embodiment, the observation indexes include: the physical and chemical properties of the test field soil, the growth indexes of the rice, the yield and composition of the rice, the irrigation amount, the rainfall, the nitrogen uptake amount of the rice, the nitrogen and phosphorus contents of the soil, the water output indexes, the water nutrient indexes, and the water depth.

[0069] It should be noted that the growth indexes of the rice include: the plant height, the tiller number, the effective ear, the leaf area, and the dry matter weight; the water output indexes include: the runoff water and the seepage water; and the water nutrient indexes include: TN, NH4+-N, NO3ˉ-N, TP, and DP of the runoff water and the seepage water.

[0070] In this optional embodiment, the sample sampling includes:

[0071] Divide the test field into several plots, select target plots and uniformly arrange sampling points in each target plot, collect surface soil samples with a depth of 0-20 cm, uniformly mix and then configure for processing, for analyzing the physical and chemical properties of the test field soil;

[0072] According to the growth and development period of rice, 12 rice samples are collected from each plot at each target period for determining the growth index of rice;

[0073] Based on the maturation period of rice, 5m 2 quadrats are selected in each plot for determining the yield and composition of rice and the nitrogen uptake of rice;

[0074] The runoff water of each plot after rainfall is collected by using a covered overflow bucket, and the seepage water in the rice field is collected by using a pre-buried iron seepage bucket for determining the water output index;

[0075] Clay soil seepage solution collectors are buried at different distances from the water inlet of each plot, and soil seepage water is collected at a preset time period in combination with irrigation and rainfall events for determining the water body nutrient index.

[0076] It should be noted that in specific embodiments, the test rice variety is Hui Feng 8, which is a medium-mature medium indica two-line hybrid rice, cultivated as a one-season medium rice in a certain province, with a full growth period of about 135 days, a plant height of about 126 cm, and generally sown in late April to early May, transplanted in late May to early June, headed in early August, and matured in mid-September; a method for controlling the water environment of a rice field by irrigation and nitrogen application includes:

[0077] I. Test content:

[0078] The test sets irrigation mode and nitrogen fertilizer operation mode as two factors, the irrigation mode includes appropriate rain irrigation and conventional flooding irrigation. Conventional flooding irrigation: keep a 10-80mm water layer on the field surface after rice seedlings turn green, do not expose the field during the entire growth period, and naturally dry for 10 days before harvesting. The key points of appropriate rain irrigation are to reduce the field water level as much as possible during drought and no rain (moderate drought stress), to postpone the irrigation time and reduce the irrigation frequency; to make full use of rainfall as much as possible (moderate waterlogging stress when the rainfall is large), to maximize the use of rainfall resources, to reduce rainfall and peak value, and to reduce irrigation water under the premise of not reducing rice yield.

[0079] The specific measures for the irrigation and drainage management of the rain-adapted irrigation are as follows: within 20 days after the rice is transplanted, all the experimental plots maintain a shallow water layer of 5-15 mm (drainage is necessary if it rains), the rice field is once irrigated to a depth of 40-60 mm after the seedlings turn green, and then the water is naturally drained (according to the underground water level observation tube, the soil moisture content and the growth of rice are determined), and then the rice field is irrigated to a depth of 40-60 mm again, and the process is repeated, during the flowering period of the rice, the water depth is maintained at 30-50 mm for one week, and the water is naturally drained 10 days before harvesting. The water depth of the rice field is adjusted as follows: during the turning green period of the rice, the rice field can be stored with water to a depth of 20 mm if it rains, during the tillering period to the jointing period, the rice field can be stored with water to a depth of 80 mm if it rains, and during the jointing period to the maturing period, the rice field can be stored with water to a depth of 100 mm if it rains, and drainage is performed if the water depth exceeds the storage depth.

[0080] In the experiment, two types of nitrogen fertilizers, slow-release fertilizer (N:P205:K20 is 20:14:16) and urea (N=46%), were used, and six nitrogen management mode treatments and one no-fertilizer treatment were set. Among them, treatments 1, 2, 4, and 5 used three times of "one base, one tiller, and one ear" fertilization, and treatments 3 and 6 used two times of "one base and one ear" fertilization, and potassium chloride was uniformly applied at the earing period of each treatment. The nitrogen type, amount, application method, and number of times of each treatment are shown in Table 1, and a completely random combination arrangement method was used, a total of 14 treatments, each treatment was repeated 3 times.

[0081] Table 1: Nitrogen management treatment (kg / hm 2 )

[0082] Treatment Base fertilizer Tiller fertilizer Ear fertilizer Total amount T1 (100% NSS-3) 96 (SS) 72 (SU) 72 (SU) 240 T2 (70% NSS-3) 48 (SS) 48 (SU) 72 (SU) 168 T3 (70% NSS-2) 96 (SS) 0 72 (SU) 168 T4 (100% NDS-3) 96 (DS) 72 (SU) 72 (SU) 240 T5 (70% NDS-3) 48 (DS) 48 (SU) 72 (SU) 168 T6 (100% NDS-2) 96 (DS) 0 72 (SU) 168 T7(0) 0 0 0 0

[0083] Note: SS represents slow-release fertilizer scattering; DS represents slow-release fertilizer depth application; SU represents urea scattering; -2, -3 represent the number of scattering times.

[0084] II. Observation content and sample collection:

[0085] 1. Observation content: basic physicochemical properties of the experimental field soil (organic matter, total nitrogen, total phosphorus, etc.), rice plant height, tiller number, effective ear number, leaf area, dry matter weight, yield and its components, irrigation amount, rainfall, nitrogen uptake, soil nitrogen and phosphorus content, runoff water, seepage water, field water depth, and TN, NH4 + -N, NO3 ˉ -N, TP, and DP in runoff water and seepage water.

[0086] 2. Sample collection:

[0087] (1) Basic soil sample: Select a large plot with uniform fertility and consistent previous crops in the test area. Set up evenly in each test of each repetition. Collect surface (0-20 cm) soil samples, then mix evenly, label, pack into cloth bags, and bring back to the room for drying.

[0088] (2) Growth indicators: Take samples at the green stage, tillering stage, jointing stage, heading stage, and grain filling stage. Take 12 plants from each plot. Measure plant height, tiller number, effective spike, leaf area, and dry matter weight in the room.

[0089] (3) Yield and its components: At the maturity stage, select 5m 2 as the yield plot.

[0090] (4) Nitrogen uptake: Measure the nitrogen uptake of the plant at the maturity stage.

[0091] (5) Water quality indicators: After rainfall, the runoff of each plot is collected through a covered overflow barrel. A self-made iron leakage barrel (30 cm in diameter and 1 m in length) is buried 60 cm underground, with the pipe opening 40 cm above the ground. The upper part is covered to prevent rainwater, dust, or insects from entering the pipe. The water level is measured every 2-3 days using a water level gauge. The daily rice field leakage is calculated based on the water level difference. Artificially bury clay soil seepage solution collectors (30 cm deep) at 3, 9, and 12 meters from the water inlet in each plot. Take soil seepage water samples at the green stage, tillering stage, jointing stage, heading stage, and grain filling stage after irrigation and rainfall (rainfall of 30 mm) ends 1, 3, and 7 days later. Then measure TN, NH4 + -N, NO3 ˉ -N, TP, and DP, etc.

[0092] III. Technical route:

[0093] As shown in Figure 2 , this test explores the effects of different irrigation modes and nitrogen management modes on nitrogen and phosphorus concentration changes, nitrogen and phosphorus loss, and yield in rice fields. By measuring plant height, tiller number, effective spike, leaf area, dry matter weight, yield and its components, irrigation volume, rainfall, nitrogen uptake, soil residual nitrogen and phosphorus content, runoff water, leakage water, field water depth, and TN, NH4 + -N, NO3 ˉ -N, TP, and DP, etc., and conducting indoor measurement and analysis, the nitrogen and phosphorus loss patterns in rice fields and the response mechanism of the water environment of rice to different nitrogen management modes under suitable rainfall irrigation conditions are studied.

[0094] IV. Expected results:

[0095] 1. To obtain the concentration changes and loss patterns of nitrogen and phosphorus in paddy fields under different water and nitrogen supply conditions, reveal the response mechanism of paddy field water quality to different water and nitrogen supply patterns, and provide a theoretical basis for regulating the paddy field water environment through water and nitrogen supply patterns.

[0096] 2. To explore the intrinsic relationship between crop water nitrogen absorption and utilization and changes and loss of nitrogen and phosphorus concentrations in paddy fields under different water and nitrogen supply conditions.

[0097] 3. The results are as follows:

[0098] (1) Number of irrigations and amount of water under different irrigation modes:

[0099] like Figure 3 As shown, the cumulative rainfall within 110 days after rice transplanting was 512.3 mm, with a maximum daily rainfall of 93.6 mm. Conventional irrigation (CI) was performed 7 times, with an irrigation volume of 345 mm, a total water consumption of 919.9 mm, and a runoff of 114.4 mm (69.0 mm during the greening stage and 47.4 mm during the grain-filling and ripening stage). The rainfall during the greening, tillering, jointing and booting, and grain-filling and ripening stages were 131.3, 54.1, 33.7, and 264.2 mm, respectively. Compared to CI, rain-adapted irrigation (RAI) was performed 4 times, reducing the irrigation volume by 42.5%. This indicates that rain-adapted irrigation significantly reduces the number of irrigations and the amount of irrigation water in paddy fields.

[0100] (2) Changes in surface water concentration in paddy fields after nitrogen application under different water and nitrogen treatments:

[0101] After applying base fertilizer, the levels of TN and NH4 in the surface water of paddy fields... + The concentrations of -N and DON increased rapidly on day 1, then decreased continuously, and stabilized by day 7. Figure 4 a, b, c). Under the two irrigation modes, compared with 60% controlled-release urea + 40% ordinary urea (N2) and 100% controlled-release urea (N3), the TN and NH4+ levels in the 100% ordinary urea (N1) treatment were significantly lower. + -N and DON concentrations increased significantly within the first 4 days after basal fertilization (P<0.05); under any nitrogen application mode, TN and NH4+ concentrations increased significantly in RAI and CI treatments. + There was no significant difference in the concentrations of -N and DON.

[0102] After applying tillering fertilizer, the TN and NH4+ in the CIN1, CIN2, RAIN1, and RAIN2 treatments were... + The concentrations of -N and DON increased rapidly on day 1, then decreased continuously, and stabilized by day 5. Figure 4 (a, b, c) Under the two irrigation modes, compared with N2, N1 has lower TN and NH4 content. +-N and DON concentrations were significantly increased (P<0.05) in the first 3 days after fertilization, and the corresponding N concentration value of N3 remained at a relatively low and stable state; under any nitrogen application mode, the TN, NH4 + -N and DON concentrations were significantly increased (P<0.05) in the first 3 days after fertilization, and the corresponding N concentration value of N3 remained at a relatively low and stable state; under any nitrogen application mode, the TN, NH4 Figure 4 a, b, c).

[0103] (3) Different forms of nitrogen and phosphorus loss in different growth stages of rice under different water and nitrogen treatments:

[0104] As shown in Table 2, about 70% of the nitrogen and phosphorus loss in the rice field under CI occurred during the tillering stage, and about 30% occurred during the jointing and booting stages. Under RAI, all nitrogen and phosphorus loss in the rice field occurred during the tillering stage. Under the conventional irrigation method, the NH4 + -N, NO3 - -N, TN, DP, and TP loss were 1.99-2.69, 0.77-1.16, 4.30-6.07, 0.14-0.16, and 0.32-0.34 kg / hm 2 , respectively, while under the shallow irrigation and deep storage method, NH4 + -N, NO3 - -N, TN, DP, and TP loss were 1.99-2.69, 0.77-1.16, 4.30-6.07, 0.14-0.16, and 0.32-0.34 kg / hm + -N, NO3 - -N and PP were the main forms of TN and TP loss.

[0105] Under the two water management methods, the TN loss under the 70% controlled-release urea + 30% ordinary urea (N2) treatment and the 100% controlled-release urea (N3) treatment was 19.7%-29.2% and 25.4%-51.7% lower than that under the 100% ordinary urea (N1) treatment, respectively, but the TP loss was very small. The variance analysis among the treatments showed that the total TN loss under the N2 and N3 treatments was significantly lower than that under the N1 treatment under the two irrigation methods, and the total TN loss under the N3 treatment could be reduced to 2.80 kg / hm 2 under RAI, and the total TP loss under the N3 treatment was significantly lower than that under the N1 treatment under RAI, which could be reduced to 0.15 kg / hm 2 , indicating that the controlled-release of nitrogen fertilizer or the 7:3 mixed application of controlled-release urea and ordinary urea could effectively reduce nitrogen loss during the early growth stage of rice, but had little effect on phosphorus loss.

[0106] Table 2: The amount of nitrogen and phosphorus loss in different forms in paddy field under different water and fertilizer management (unit: kg / hm 2 )

[0107]

[0108]

[0109] Note: Lowercase letters indicate the difference between treatments at the 5% level (P < 0.05, same below), same below.

[0110] (4) The amount of nitrogen and phosphorus loss in different forms in paddy field under different water and nitrogen management:

[0111] As shown in Table 3, under CI, the amount of NH4 + -N, NO3 - -N, TN, DP and TP loss in paddy field during the whole growth period was 8.98-13.83, 1.40-2.83, 14.16-19.38, 0.22-0.32 and 0.37-0.49 kg / hm 2 , respectively, while under RAI, the amount of NH4 + -N, NO3 - -N, TN, DP and TP loss in paddy field during the whole growth period was reduced by 23.5%-28.1%, 12.9%-37.5%, 22.8%-32.0%, 5.0%-36.4% and 16.2%-33.3%, respectively, compared with CI. Among them, NH4 + -N, NO3 - -N and DP were the main forms of TN and TP loss, and the reduction of the amount of nitrogen and phosphorus loss in different forms under RAI was mainly in the growth stage from green-up to jointing and booting, which was the key period for reducing the loss of nitrogen and phosphorus in paddy field.

[0112] Under the two water management methods, compared with N1, the amount of TN loss in N2 and N3 was reduced by 15.1%-25.2% and 20.9%-26.4%, respectively, and the amount of TP loss was reduced by 18.4%-24.5% and 20.4%-31.6%, respectively. The variance analysis among the treatments showed that under the two water management methods, the total amount of NH4 + -N, NO3 - -N and TN loss in N2 and N3 was significantly lower than that in N1, and the total amount of NH4 + -N, NO3 - -N and TN loss in N3 was lower than that in N2, but there was no significant difference. The total amount of DP and TP loss in the three fertilizer treatments was N1 > N2 > N3, but there was no significant difference among the treatments.

[0113] Table 3: Different water and fertilizer management of rice field each form of nitrogen and phosphorus leakage loss (unit: kg / hm 2 )

[0114]

[0115]

[0116] (5) TN runoff and leakage loss under different water and nitrogen treatments during the whole growth period of rice:

[0117] From Figure 5 (Notes: the same index after different letters represent the difference reaches 0.05 significant level; the same below) can be seen that under the two irrigation modes, compared with N1, the TN runoff and leakage loss of N2 and N3 significantly reduced; under any nitrogen application mode, RAI significantly reduced the TN runoff and leakage loss compared with CI; the TN runoff and leakage loss of CIN1 treatment was the largest, and the TN runoff and leakage loss of RAI treatment was the smallest

[0118] (6) Effect of different water and nitrogen treatments on rice plant height:

[0119] From Figure 6 can be seen that under any nitrogen application mode, compared with CI, the rice plant height at each growth stage under RAI increased. Under any irrigation mode, compared with N1 treatment, the plant height of N2 and N3 treatments at the jointing stage decreased, while the plant height of N2 and N3 treatments at the booting stage-mature stage increased, and the plant height of N2 treatment increased more than that of N3 treatment. Compared with CIN1, the plant height of rice at the booting stage-mature stage increased under RAI coupled with N2 or N3.

[0120] (7) Effect of different water and nitrogen treatments on rice leaf SPAD value:

[0121] From Figure 7 can be seen that the SPAD value of rice leaf under each treatment gradually increased from the jointing stage to the filling stage, reached the maximum at the filling stage, and rapidly decreased at the mature stage. Under any nitrogen application mode, compared with CI, the SPAD value at the jointing stage-filling stage increased under RAI, while the SPAD value at the mature stage had no significant difference between the two irrigation modes (P>0.05). Under any irrigation mode, compared with N1 treatment, the SPAD value at the jointing stage-booting stage decreased under N2 and N3 treatments, while the SPAD value at the booting stage-mature stage increased under N2 and N3 treatments, and the difference reached a significant level at the mature stage (P<0.05). Compared with CIN1, RAI coupled with N2 or N3 was beneficial to improve the SPAD value of rice leaf during the growth period.

[0122] (8) Effect of different water and nitrogen treatments on rice dry matter and crop growth rate:

[0123] From Table 4, Table 5, it can be seen that the accumulation of dry matter of each organ at the heading stage generally showed: stem > leaf > ear; the accumulation of dry matter of each organ at the mature stage showed: ear > stem > leaf, indicating that with the growth process of rice, dry matter gradually transferred from stem and leaf to ear. Under the same irrigation treatment, the accumulation of dry matter of ear at different growth stages showed that N2 treatment was significantly higher than N1 treatment, although it was not significant under the flooding irrigation treatment, but the accumulation of dry matter under N2 treatment was higher than that under N1 treatment, indicating that the treatment of controlled-release urea 60% + ordinary urea 40% was more conducive to the accumulation of dry matter of ear. At the mature stage, compared with the flooding irrigation treatment, the accumulation of dry matter of ear under N1, N2 and N3 treatments increased by 4.1%, 3.5% and 2.2% respectively, indicating that the appropriate rain irrigation was more conducive to the accumulation of dry matter of ear at the mature stage. In terms of total dry matter accumulation, compared with CI treatment, the total dry matter under N1, N2 and N3 treatments increased by 5.6%, 5.1% and 3.5% respectively under RAI treatment at the mature stage, and the accumulation of dry matter reached the maximum under RAI-N2 treatment, indicating that the appropriate rain irrigation combined with controlled-release urea 60% + ordinary urea 40% was conducive to the accumulation of dry matter. Compared with N1, N2 and N3 significantly improved the growth rate of crops under the two irrigation measures; compared with CI treatment, RAI treatment increased the growth rate of crops under N1 and N2 treatments, and the maximum increase was under N2 treatment. It is shown that the appropriate rain irrigation combined with controlled-release urea 60% + ordinary urea 40% is conducive to the accumulation of dry matter and the improvement of crop growth rate.

[0124] Table 4: Changes of dry matter of rice under different treatments at the heading stage (unit: kg / hm 2 )

[0125]

[0126] Table 5: Changes of dry matter of rice under different treatments at the mature stage (unit: kg / hm 2 )

[0127]

[0128] (9) Effects of different water and nitrogen treatments on the number of tillers and the earing rate of stem sprouts of rice:

[0129] From Table 6, the number of tillers is different with different growth periods, irrigation modes and fertilization systems. Under the same irrigation mode, the number of tillers of each treatment is N1>N2>N3. Under the same nitrogen level, the number of tillers of CI and RAI treatments is not significantly different, while the number of tillers of CI treatment is significantly greater than that of RAI treatment at the jointing and heading stages, and the rate of stem tillers into ears of RAI treatment is higher than that of CI treatment, indicating that the appropriate rain irrigation combined with 60% controlled release urea + 40% ordinary urea or 100% controlled release urea is beneficial to reduce ineffective tillers and improve the rate of stem tillers into ears.

[0130] Table 6: Number of tillers and rate of stem tillers into ears of rice under different water and nitrogen treatments

[0131]

[0132] (10) Effect of different water and nitrogen treatments on rice yield and constituent factors:

[0133] The effects of different irrigation measures and controlled release urea and ordinary urea ratio on rice yield and yield constituent factors are different. As shown in Table 7, under the two irrigation measures, the yield of N2 and N3 treatments is significantly higher than that of N1 treatment, and under CI treatment, N2 and N3 increase the yield by 10.7% and 6.7% respectively compared with N1; under RAI treatment, N2 and N3 increase the yield by 14.3% and 9.1% respectively compared with N1, which shows that the yield increase of rice under light rain irrigation treatment is greater than that under flooding irrigation treatment. Compared with CI treatment, N1 increases the yield by 2.7%, N2 increases the yield by 6%, and N3 increases the yield by 5% under RAI treatment, indicating that appropriate rain irrigation is beneficial to improve crop yield. In terms of yield constituent factors, the effective panicles, grains per panicle, seed setting rate and 1000-grain weight under RAI treatment are higher than those under CI treatment, and under the two irrigation measures, N2 and N3 increase the effective panicles, grains per panicle, seed setting rate and 1000-grain weight compared with N1. Compared with other treatments, the seed setting rate under CI-CU and RAI-CU treatments is significantly reduced, which shows that the application of ordinary urea alone can reduce the seed setting rate of rice. Under the treatment of appropriate rain irrigation combined with controlled release urea + ordinary urea, the yield of rice is the highest, and under the treatment of flooding irrigation combined with ordinary urea, the yield of rice is the lowest.

[0134] Table 7: Effect of different water and nitrogen treatments on rice yield and yield constituent factors

[0135]

[0136] (11) Effect of different water and nitrogen treatments on nitrogen uptake and nitrogen use efficiency of rice:

[0137] From Table 8, under the same irrigation mode, the nitrogen uptake of N2 treatment was significantly higher than that of N1 and N3. The nitrogen uptake of each treatment under RAI was higher than that under CI, and the difference between N2 and N3 reached a significant level. The nitrogen use efficiency was also greatly improved, specifically, N1 increased by 17.8%, N2 increased by 24.7%, and N3 increased by 15.9%. The water-nitrogen interaction effect between RAI and N2 could significantly improve the nitrogen uptake and nitrogen use efficiency of rice.

[0138] Table 8: Effect of different water-nitrogen treatments on nitrogen uptake and nitrogen use efficiency of rice

[0139]

[0140] 4、Conclusion:

[0141] (1) Compared with CI, RAI significantly reduced the irrigation frequency (-3) and irrigation volume (-41.7%), and significantly increased the rainfall utilization rate (+16.2%).

[0142] (2) Compared with CI, the N and P concentrations in the rice field surface water of RAI slightly increased, but RAI significantly reduced the runoff frequency (-3), runoff volume (-45.8%), and leakage volume (-22.1%) during the growth period of the rice field, significantly reducing the runoff and leakage loss of TN and TP in the rice field (-16.2-42.7%); compared with N1, the N and P concentrations in the rice field surface water of N2 and N3 decreased, significantly reducing the runoff and leakage loss of TN and TP in the rice field (-11.2-33.5%). The N and P runoff and leakage loss of RAIN3 was the smallest, followed by RAIN2.

[0143] (3) Compared with CI, RAI was beneficial to improving the SPAD value of rice leaves from the jointing stage to the grain filling stage, the stem tiller earing rate, the crop growth rate, the dry matter accumulation and its distribution proportion to the ear, the plant nitrogen uptake, the effective panicle number, the grain number per panicle, the seed setting rate, the thousand-grain weight, the grain yield, and the nitrogen use efficiency.

[0144] (4) Under the same irrigation level, compared with N1, N2 and N3 were beneficial to improving the SPAD value of rice leaves, the stem tiller earing rate, the crop growth rate, the dry matter accumulation and its distribution proportion to the ear, the plant nitrogen uptake, the effective panicle number, the grain number per panicle, the seed setting rate, the thousand-grain weight, and the grain yield. N2 further improved the grain yield and nitrogen use efficiency compared with N3.

[0145] (5) RAI reduces irrigation water, runoff and leakage, N2 or N3 reduces N, P concentration of paddy field water, and the coupling of the two significantly reduces N, P runoff and leakage loss in paddy field; RAIN2 and RAIN3 improve the nitrogen nutrition of plants, increase the stem tiller earing rate of rice, promote the accumulation of dry matter and its distribution to grains, thereby obtaining high yield.

[0146] The above merely describes preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for regulating the water environment of paddy fields by applying nitrogen through irrigation, characterized in that, The method includes: S1. Based on the rainfall characteristics of the target area and the growth and development stage of rice, design and execute field trials of irrigation and nitrogen supply patterns; S2. Based on the results of field experiments, analyze the concentration changes and loss patterns of nitrogen and phosphorus in paddy water under irrigation and nitrogen supply modes, so as to determine the response mechanism of paddy water quality to irrigation and nitrogen supply modes. S3. Based on the analysis and measurement results of the field experiment, obtain the correlation between the water and nitrogen use efficiency of rice and the change and loss patterns of nitrogen and phosphorus concentrations in paddy fields under irrigation and nitrogen supply modes. S4. By combining the response mechanism of paddy field water quality to irrigation and nitrogen supply patterns, and the correlation between rice water nitrogen use efficiency and the variation and loss patterns of paddy field nitrogen and phosphorus concentrations, determine the water-nitrogen coupling pattern for rice production in the target area, so as to achieve the regulation of paddy field water environment.

2. The method for regulating paddy field water environment by applying nitrogen through irrigation according to claim 1, characterized in that, The irrigation modes include: rainfall-appropriate irrigation and conventional flooding.

3. The method for regulating the water environment of paddy fields by applying nitrogen through irrigation according to claim 2, characterized in that, The rainfall-appropriate irrigation includes: Experimental fields were set up in the target area. Based on the rainfall characteristics of the target area, irrigation was carried out within 20 days after the rice was transplanted to the experimental fields to maintain the water depth on the field surface at 5-15 mm in order to promote the rice to enter the greening stage. After the rice enters the greening stage, the first irrigation is carried out, and the water depth on the field is irrigated to 40-60mm and then allowed to dry naturally. The soil moisture and rice growth are monitored by the pre-buried groundwater level monitoring pipes. Based on the monitoring results and the growth and development stages of rice, irrigate periodically until the water depth on the field is 40-60 mm and then naturally dries up, until the rice enters the flowering stage. During the flowering stage, maintain the water depth on the field at 30-50 mm for one week. Ten days before the rice harvest, stop irrigation and allow the rice to dry naturally.

4. The method for regulating the water environment of paddy fields by applying nitrogen through irrigation according to claim 3, characterized in that, The appropriate irrigation also includes adjusting the water depth in paddy fields according to the rainfall characteristics of the target area and the growth and development stage of rice.

5. The method for regulating the water environment of paddy fields by applying nitrogen through irrigation according to claim 4, characterized in that, The adjustment of paddy field water depth based on rainfall characteristics in the target area and the growth and development stage of rice includes: During the rice's greening period, if it rains, the paddy field should be filled with water up to 20mm. If it rains during the tillering to jointing stage of rice, the paddy field should be filled with water up to 80 mm. If it rains during the rice's jointing stage to maturity, the paddy field should be filled with water up to 100mm. If rainfall in the target area exceeds the water storage depth required for the corresponding stage during the rice's growth and development, drainage will be carried out to promote the rice's growth and development.

6. The method for regulating paddy field water environment by applying nitrogen through irrigation according to claim 1, characterized in that, The nitrogen supply modes include: 6 nitrogen fertilizer management mode treatments and 1 no-fertilizer treatment.

7. The method for regulating paddy field water environment by applying nitrogen through irrigation according to claim 6, characterized in that, The nitrogen fertilizers include: slow-release fertilizers and urea.

8. The method for regulating the water environment of paddy fields by applying nitrogen through irrigation according to claim 1, characterized in that, The measurements include: observation of indicators and sample collection.

9. A method for regulating the water environment of paddy fields by applying nitrogen through irrigation according to claim 8, characterized in that, The observation indicators include: the physical and chemical properties of the soil in the experimental field, rice growth indicators, rice yield and composition, irrigation amount, rainfall, nitrogen uptake by rice, soil nitrogen and phosphorus content, water output indicators, water nutrient indicators, and field surface water depth.

10. A method for regulating the water environment of paddy fields by applying nitrogen through irrigation according to claim 9, characterized in that, The sample collection includes: The experimental field was divided into several plots. Target plots were selected and sampling points were evenly distributed in each target plot. Topsoil samples from a depth of 0 to 20 cm were collected, mixed evenly, and then processed for analysis of the physical and chemical properties of the experimental field soil. Based on the growth and development stages of rice, 12 rice samples were collected from each plot at each target stage to determine rice growth indicators. Based on the rice maturity period, a 5m section was selected within each plot. 2 The quadrats are used for determining rice yield and composition, as well as rice nitrogen uptake. The overflow bucket with a lid is used to collect runoff from various plots after rainfall, and seepage water from paddy fields is collected through pre-buried iron seepage buckets to measure water output indicators. Soil seepage solution collectors were buried at different distances from the water inlet of each plot. Soil seepage water was collected at preset time periods in conjunction with irrigation and rainfall events to determine the nutrient indicators of the water body.

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