Method for controlling agricultural non-point source pollution of rice field ditches

Abstract

The invention discloses a method for controlling agricultural non-point source pollution in a rice field ditch, which comprises the following steps of: planting water spinach in the rice field ditch 7-10 days before the rice field is soaked, and spreading a periphyton growth inducing artificial carrier in the ditch after the water spinach is planted, so as to induce the growth of periphyton in the rice field. Through staggered growth of the water spinach and the periphyton, the ditch nitrogen and phosphorus are stored in the early growth stage of the rice by utilizing the'microbial nutrient library 'characteristic of the periphyton, and meanwhile, the water spinach is utilized to absorb the nitrogen and phosphorus in the middle and later growth stages of the rice, so that migration and loss of the nitrogen and phosphorus in the ditch are comprehensively intercepted, and the migration process of agricultural non-point source pollutants in the rice field is intercepted. The method is convenient to operate and good in effect, nutrients such as nitrogen and phosphorus in the ditch water body can be effectively absorbed, certain economic benefits can be generated, and finally the migration and propagation risks of the nutrients in the ditch are reduced.

Description

Technical Field

[0001] The invention belongs to the field of non-point source pollution prevention and control, and particularly relates to a method for controlling agricultural non-point source pollution in rice field ditches. Background Art

[0002] Agricultural non-point source pollution refers to non-point source pollution that occurs in agricultural areas. It is a pollution mode in which pesticides, nitrogen, phosphorus and other organic or inorganic pollutants enter environmental water bodies through rice field drainage, surface runoff and other means during precipitation or irrigation. At present, in terms of agricultural non-point source pollution prevention and control, according to the transmission process from pollution source to sink, we can start from four directions (i.e. the "4R" plan for agricultural non-point source pollution control) to prevent and control non-point source pollution, and supplement it with appropriate environmental management measures to truly control non-point source pollution.

[0003] However, rice fields are still the main source of agricultural non-point source pollution. They spread pollution to surrounding water bodies through ditch discharge, causing eutrophication of nitrogen and phosphorus concentrations in downstream water bodies. However, the current prevention and control technology of non-point source pollution in rice fields still cannot effectively ensure that the water quality of rice field drainage meets the standards. Therefore, more efficient and environmentally friendly technologies are needed to control the discharge of non-point source pollution in rice fields, especially to improve the water quality standards of rice field effluent. Summary of the invention

[0004] The purpose of the present invention is to provide a method for controlling agricultural non-point source pollution in rice field ditches in view of the shortcomings of the above-mentioned prior art.

[0005] To achieve the above object, the present invention adopts the following technical solution:

[0006] A method for controlling agricultural non-point source pollution in rice field ditches, comprising:

[0007] 7 to 10 days before paddy fields are flooded, water spinach is planted in the ditches of the rice fields. After planting, artificial carriers for inducing the growth of periphyton are spread in the ditches to induce the growth of periphyton in the rice fields.

[0008] As a preferred embodiment, the planting density of water spinach is 24-26 plants / m 2 This density can not only ensure the normal growth of water spinach, but also ensure its sufficient nitrogen and phosphorus absorption capacity.

[0009] As a preferred implementation manner, the thickness of the soil layer at the bottom of the ditch for planting water spinach is ≥ 25 cm, ensuring that the roots of the water spinach have sufficient growth space.

[0010] As a preferred embodiment, the application rate of the artificial carrier for inducing the growth of peripheral biological clusters is 24-26 kg / ha.

[0011] As a preferred embodiment, the method for constructing the pericyte growth inducing artificial carrier is as follows:

[0012] Sodium alginate was dissolved in the culture medium of the periphyton organism and then cross-linked with the CaCl2 solution to form a spherical carrier;

[0013] The components of the periphyton biological culture solution are: NaNO3 4-5 g / L, KH2PO4 5-6 g / L, MgSO4·7H2O 2-3 g / L, NaHCO3 1-2 g, CaCl2·2H2O 1-2 g / L, and soil extract 100 mL / L.

[0014] The present application simplifies the commonly used culture medium for periphyton organisms, which is usually improved on the basis of WC culture medium. Some trace nutrients, including VB and biotin, are removed from the culture medium of the present application, and combined with soil extract prepared based on paddy field soil, the cost of large-scale promotion and application of the technology can be reduced without affecting the rapid growth of periphyton organisms in paddy fields. The culture medium of the present application is based on common inorganic salt components combined with soil extract, which can promote the rapid proliferation of periphyton organisms, so that its biomass reaches at least 1200kg / ha before the panicle differentiation stage of rice growth.

[0015] As a preferred embodiment, the soil extract is: after drying the paddy field soil, adding carbonate / bicarbonate solution to adjust the pH to 8-10, then adding activated carbon for treatment and filtering, the resulting filtrate is the soil extract. In the present application, carbonate solution / bicarbonate solution and activated carbon are used for soil extraction, and the carbonate solution / bicarbonate solution adjusts the solution pH to alkaline, which is suitable for the growth of periphyton; activated carbon can adsorb organic matter, heavy metal ions and other substances in the soil extract, reducing the impact of exogenous substances introduced by the soil extract on the growth of periphyton.

[0016] As a preferred embodiment, the paddy field soil is the soil in the surface layer of 0-20 cm of the paddy field.

[0017] As a preferred embodiment, when preparing the soil extract, the amount of dried soil used is 2-2.2 kg / L solution.

[0018] As a preferred embodiment, when preparing the soil extract, the amount of activated carbon used is 30-50 g / L solution.

[0019] As a preferred embodiment, the biomass of the peripheral organisms in the rice field reaches more than 1200 kg / ha before the panicle differentiation stage.

[0020] The principle of the technical solution of the present invention is as follows:

[0021] By applying artificial carriers to the ditches, rapid and massive growth of periphyton in the ditches can be induced. The artificially induced growth of periphyton is like a "microbial nutrient bank" with great potential, which can reduce the concentration of nitrogen and phosphorus in the water body by storing nitrogen and phosphorus. In the ecological management of canals, if the concentrations of ammonia nitrogen and total nitrogen in polluted river water are high, plants with strong nitrogen absorption capacity should be selected for matching; if the total phosphorus concentration is high, plants with strong phosphorus absorption capacity should be selected for matching; if both nitrogen and phosphorus are high, plants with strong nitrogen and phosphorus absorption capacity should be selected for matching. The plant planting density should be 25 plants / m 2 . Based on the planning of ditches around the experimental field, as well as the plant landscape utility, pollution removal potential, potential economic benefits and physical and chemical properties of ditch water quality, this application selected water spinach, which has both efficient nitrogen and phosphorus absorption capacity and economic benefits, as the target aquatic plant, and utilized the time and space differences between the growth of periphyton and water spinach, and the fast growth characteristics of periphyton. In the early stage of rice growth, the absorption capacity of periphyton for nitrogen and phosphorus was used to reduce the concentration of nitrogen and phosphorus in the ditch water, intercept the migration process of agricultural non-point source pollutants in rice fields, and reduce the risk of migration and pollution transmission of nitrogen and phosphorus in rice fields; taking advantage of the characteristics of water spinach that it grows slowly and can grow in the middle and late stages of rice growth, the absorption effect of water spinach on ditch nitrogen and phosphorus in the late stage of rice growth was brought into play, providing a method for controlling agricultural non-point source pollution in rice field ditches that combines the "early" interception of periphyton and the "middle and late" absorption of water spinach.

[0022] In addition, the research results of this application show that the combined use of pericarp and water spinach produced a synergistic effect. Compared with planting water spinach alone or broadcasting pericarp, the effects of reducing nitrogen and phosphorus content in the overlying water and improving water quality were enhanced. The growth cycle of water spinach is longer than that of surrounding organisms. Water spinach has not yet grown in the early stage, and the growth of surrounding organisms will not be affected by shading, while surrounding organisms can grow rapidly. In the present application, surrounding organisms can reach at least 1200kg / ha before the ear differentiation stage. Since surrounding organisms are the first to grow and play a role, we analyzed that the presence of surrounding organisms may also promote the growth of water spinach. For example, after the surrounding organisms carry out biological transformation of the nutrients stored in the body, they release the stored nutrients through concentration difference and cell apoptosis, thereby increasing the content of active nutrients in the soil (such as bioavailable phosphorus, ammonium nitrogen, etc.). The release of such active nutrients provides nutrients for the growth of water spinach, thereby promoting better growth of water spinach, thereby enhancing the water spinach's ability to absorb nitrogen and phosphorus. After the water spinach grows, surrounding organisms still maintain a large biomass, and there may be a synergistic effect of interception / absorption with water spinach, thereby further improving the water quality.

[0023] The present invention has the following beneficial effects:

[0024] (1) In order to make periphyton grow rapidly in rice fields and cooperate with water spinach, the present application has improved the periphyton culture medium. Compared with conventional periphyton culture medium, the addition of trace elements is reduced, and the culture medium is prepared by only using inorganic salts combined with soil extracts from rice fields, ultimately achieving rapid induction of the growth of periphyton in rice fields, so that the biomass of periphyton in rice fields can reach at least 1200kg / ha before the panicle differentiation period of rice growth, while also reducing the production cost of the carrier. Using the in-situ soil of rice fields, combined with the addition of soil extracts obtained by carbonate / bicarbonate and activated carbon treatment, can promote the rapid growth of microorganisms that are difficult to artificially induce and have powerful functions in periphyton, thereby efficiently promoting the rapid film formation of periphyton, and improving the biodiversity in periphyton, so that it can induce periphyton to form a dense community at the soil-water interface in a short period of time.

[0025] (2) The method of the present invention is easy to operate and has good effects. The artificial carrier preparation method provided is convenient and simple. The application operation method of the artificial carrier is convenient, similar to the fertilizer application process in the rice production process, and the operation method is simple.

[0026] (3) Compared with the use of either Achyranthes bidentata or Ipomoea batatas alone to intercept / absorb nitrogen and phosphorus, the combined use of Achyranthes bidentata and Ipomoea batatas produced a synergistic effect, further reducing the nitrogen and phosphorus content in the overlying water, improving the effluent quality, and preventing the occurrence of non-point source pollution in rice fields.

[0027] (4) This biotechnology originates from indigenous microorganisms and cash crops in rice fields. Therefore, compared with the introduction of exogenous materials, this technology has extremely high environmental safety and economic benefits, which can increase the income from rice cultivation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the total nitrogen concentration in the ditch water of the experimental group and the control group during different rice growth periods.

[0029] Figure 2 It is the total phosphorus concentration in the ditch water of the experimental group and the control group during different rice growth periods.

[0030] Figure 3 Comparison of water quality at the ditch outlet between the experimental group and the control group during rice maturity DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific implementation methods.

[0032] The embodiment uses the rice field ditch agricultural non-point source pollution to include the following steps:

[0033] Weigh 4-5 g NaNO3, 5-6 g KH2PO4, 2-3 g MgSO4·7H2O, 1-2 g NaHCO3, and 1-2 g CaCl2·2H2O, dissolve in 0.9 L distilled water, add 100 mL soil extract, mix well, and prepare 1 L peritrichous biological culture solution. The pH of the peritrichous biological culture solution is 7-8, which is weakly alkaline.

[0034] The preparation method of soil extract is as follows: take 0-20cm paddy field surface soil samples (excluding surrounding organisms) from the paddy field and dry them at 105-115℃ until constant weight. Take 200-220 grams of dry soil sample and put it into a 500mL container, and add 100mL of 0.5M sodium bicarbonate solution. After stirring the soil with a glass rod, add half a spoonful (about 4g) of activated carbon to the sample. After shaking vigorously for 1-2 minutes, let the sample stand for 5-10 minutes. After filtering, the filtrate obtained is the soil extract.

[0035] The preparation method of the Zhoucong biological induction carrier is as follows: 1L of Zhoucong biological culture fluid is used to dissolve 18-22g of sodium alginate to prepare a sodium alginate solution; the sodium alginate solution is dripped into 2L of CaCl2 solution with a mass concentration of 1.8-2.2% by using a peristaltic pump to form a spherical carrier with a diameter of 2-3mm; the prepared carrier is cross-linked at 4°C for 18-24h and then used for standby;

[0036] Plant water spinach seeds in the ditches of the paddy fields 7 to 10 days before paddy fields are soaked. The planting density is 24-26 plants / m 2 .

[0037] The method of using the peripheral biological induction carrier is as follows: after the planting of water spinach in the ditch is completed, 24-26kg / ha of artificial carrier is applied to the ditch 7-10 days before paddy field flooding to induce the rapid growth of peripheral biological.

[0038] Examples 1 to 3 take the rice field experiment in Baitu Village, Baitu Town, Jurong City, Jiangsu Province as an example to illustrate the application effect of the method of the present invention.

[0039] In Baitu Village, Baitu Town, Jurong City, Jiangsu Province, four similar ditches around the field were selected, and the amount of fertilizer applied to the rice field was the same. Ditch 1, Ditch 2, and Ditch 3 were set to apply Zhoucong biological artificial carriers (control 1), plant water spinach (control 2), apply Zhoucong biological artificial carriers + plant water spinach (experimental group), and Ditch 4 was a blank control without water spinach and artificial carriers. The artificial carrier application rate in Examples 1 to 3 was uniformly 25 kg / ha, and the water spinach planting density was 25 plants / m 2, and the application / planting was done 7 days before the paddy field was soaked. The composition of the Zhoucong biological culture solution was: NaNO34.5 g, KH2PO45.5 g, MgSO4·7H2O2.5g, NaHCO31.5 g, CaCl2·2H2O 1.5g, and soil extract 100mL / L. The sampling period was the entire rice-growing period. Sampling began on June 25, and the overlying water in the ditch was collected once a week until October 15. The overlying water in the ditch was collected on October 15, and its water quality was evaluated using the comprehensive water quality index method. The entire sampling period was divided into four periods: the greening period, the tillering period, the panicle differentiation period, and the heading and flowering period. The overlying water was stored in a polyvinyl chloride plastic bottle, and there was a pre-frozen ice pack in the sampling box. The sample was placed in the sampling box for low-temperature storage and quickly transported back to the laboratory. The sample was immediately frozen in the laboratory until further analysis of the sample later.

[0040] Example 1 Comparison of nitrogen concentration in the overlying water of each ditch during different rice growth periods

[0041] This example compares the total nitrogen concentration in the ditch overlying water in the experimental group and the control group. The nitrogen removal effect of the experimental group and the two control groups (control group 1 and 2) is better than that of the blank control group. The total nitrogen concentration in the ditch overlying water in the experimental group and the two control groups is as follows: Figure 1 As shown, for ditches where carriers were applied alone to induce the growth of periphyton, the total nitrogen concentration in the water varied between 1.94-48.32 mg / L; for ditches where water spinach was planted, the total nitrogen concentration in the water varied between 1.24-51.32 mg / L. Comparison of the two shows that periphyton exhibited a stronger nitrogen removal effect in the water body in the early stages of rice growth (greening and tillering stages), and as water spinach grew, it showed a stronger nitrogen removal ability than periphyton in the late rice growth period. When periphyton was used in combination with water spinach, it was found that its nitrogen removal effect was stronger than that of ditches where periphyton and water spinach were applied alone during this rice growth period. This shows that the combination of periphyton and water spinach exhibits a stronger nitrogen removal effect. In addition, the biomass of periphyton was determined through a sampling survey, and the total biomass of periphyton in the experimental group throughout the rice growing season was about 3.0 t / ha.

[0042] Example 2 Comparison of total phosphorus concentration in the overlying water of each ditch during different rice growth periods

[0043] This example compares the total phosphorus concentration in the ditch overlying water in the experimental group and the control group. The phosphorus removal effect of the experimental group and the two control groups (control group 1 and 2) is better than that of the blank control group. The total phosphorus concentration in the ditch overlying water in the experimental group and the two control groups is as follows: Figure 2As shown, for ditches where carriers were applied alone to induce the growth of periphyton, the total phosphorus concentration in the water varied between 0.05-0.25 mg / L; for ditches where water spinach was planted, the total nitrogen concentration in the water varied between 0.01-0.21 mg / L. Comparison of the two shows that water spinach showed a stronger effect in removing phosphorus from the water body in the early stages of rice growth (greening and tillering stages), and as periphyton grew, its phosphorus removal ability in the late stage of rice growth was close to that of water spinach, which shows that water spinach showed a better effect in phosphorus removal. After using periphyton and water spinach together, it was found that their phosphorus removal effect was stronger than that of ditches where periphyton and water spinach were applied alone during this rice growth period, especially in the middle and late stages of rice growth (tillering and panicle differentiation stages). This shows that the combination of periphyton and water spinach showed a stronger phosphorus removal effect.

[0044] Example 3 Comparison of water quality of overlying water in various ditches during rice harvest period

[0045] This example compares the water quality of the overlying water in the experimental group and the control group 1 and 2. Figure 3 As shown in the figure, we compared the water quality of the overlying water in each ditch during the rice harvest period. It can be seen intuitively that the average value of the comprehensive water quality index CWQI of the experimental ditch with the combination of periphyton and water spinach is 5.72, while the average values ​​of CWQI of the induced periphyton growth group and the water spinach planting group in the control group are 6.83 and 6.73 respectively, which means that the water quality of the experimental group is Class V water, which meets the target water quality requirements and can be used in agricultural water use areas and general landscape waters. The average CWQI of the control group shows that its water quality is one level lower than the target water quality, which is not black and smelly. Class V water, which proves that whether the use of periphyton or water spinach alone can achieve good results, the combined use of artificially induced periphyton and water spinach can effectively improve the water quality of ditch water and effectively reduce the risk of nitrogen and phosphorus in ditch water migrating to downstream water bodies.

[0046] The calculation method of the comprehensive water quality index in this embodiment is as follows:

[0047] Based on the single factor water quality identification method, it is composed of the average value of the sum of the single factor water quality identification index, the comparison result between the representative water quality category and the functional zoning category, and the number of water quality indicators that are inferior to the functional area standard among the indicators participating in the overall water quality evaluation. The calculation formula is:

[0048] CWQI=(X1.X2)MN (1)

[0049]

[0050] In the formula: XWQI is the comprehensive calculation result of all participating indicators in the evaluation system, (X1.X2) is the average value of X1.X2 calculated by all participating evaluation indicators; M is the number of single indicators that are inferior to the water environment functional area target among the water quality indicators participating in the comprehensive water quality evaluation, which is the second decimal place of the decimal part of CWQI; N is the comparison result of the comprehensive water quality category and the water body functional area category, which is the third decimal place of the decimal part of CWQI, and the single factor identification index P that passes the evaluation is i The number of M in is not 0. In this embodiment, the indicators X1 and X2 are nitrogen and phosphorus concentrations.

[0051] The comprehensive water quality index classification standards are shown in Table 1.

[0052] Table 1 Comprehensive water quality classification criteria

[0053] Comprehensive Water Quality Index CWQI Comprehensive water quality level [1.0，2.0] Category I (2.0，3.0] Category II (3.0，4.0] Category III (4.0，5.0] Category IV (5.0，6.0] Category V (6.0，7.0] Not black, smelly, inferior to Class V ＞7 Black and smelly inferior grade V

Claims

1. A method for controlling agricultural non-point source pollution in rice field ditches, characterized in that: include: 7 to 10 days before paddy fields are flooded, water spinach is planted in the ditches of the rice fields. After the water spinach is planted, artificial carriers for inducing the growth of periphyton are spread in the ditches to induce the growth of periphyton in the rice fields.

2. The method according to claim 1, characterized in that The planting density of the water spinach is 24-26 plants / m 2 .

3. The method according to claim 1, characterized in that The application rate of the artificial carrier for inducing the growth of peripheral biological organisms is 24-26 kg / ha.

4. The method according to claim 1, characterized in that: The thickness of the soil layer at the bottom of the ditch for planting water spinach should be ≥25cm.

5. The method according to claim 1, characterized in that The method for constructing the pericyte growth inducing artificial carrier is as follows: Sodium alginate was dissolved in the culture medium of the periphyton organism and then cross-linked with the CaCl2 solution to form a spherical carrier; The composition of the pericyte culture solution is: NaNO3 4-5 g / L, KH2PO4 5-6 g / L, MgSO4·7H2O 2-3 g / L, NaHCO3 1-2 g, CaCl2·2H2O 1-2 g / L, and soil extract 100 mL / L.

6. The method according to claim 5, characterized in that The soil extract is prepared by drying paddy field soil, adding carbonate / bicarbonate solution to adjust the pH to 8-10, then adding activated carbon for treatment and filtering, and the obtained filtrate is the soil extract.

7. The method according to claim 6, characterized in that The paddy field soil is the soil in the surface layer of 0-20 cm of the paddy field.

8. The method according to claim 6, characterized in that When the soil extract is prepared, the amount of dried soil used is 2-2.2 kg / L solution.

9. The method according to claim 8, characterized in that When the soil extract is prepared, the amount of activated carbon used is 30-50 g / L solution.

10. The method according to claim 1, characterized in that The biomass of the periphyton in the rice field reaches more than 1200 kg / ha before the panicle differentiation stage.

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