Rice-macrobrachium rosenbergii co-cropping nitrogenous fertilizer application-reducing and efficiency-increasing planting and breeding method

Abstract

The invention belongs to the technical field of rice field aquaculture, and particularly relates to a rice-macrobrachium rosenbergii co-cropping nitrogenous fertilizer application reducing and efficiency improving planting and breeding method. The method comprises the steps that S1, nitrogenous fertilizer application reduction treatment is conducted on the rice field, specifically, nitrogenous fertilizer urea obtained after application reduction is completely applied to 0-15 cm of plough layer soil of the rice field, and the nitrogenous fertilizer amount obtained after application reduction is 40%-80% of the nitrogenous fertilizer amount before application reduction; step S2, transplanting rice seedlings: sowing and raising rice seedlings in the first ten days of May every year, and transplanting the rice seedlings to the rice field after the rice seedling age reaches 25-30 days; 3, macrobrachium rosenbergii is put, wherein macrobrachium rosenbergii seeds are put in the morning of a sunny day in the rice sealing period according to the density of 4.5-90 thousand / hm < 2 > for breeding; s4, harvesting: harvesting adult macrobrachium rosenbergii for sale when the water temperature of the rice field is lower than 20 DEG C, and harvesting rice when the rice is mature. By the adoption of the rice-macrobrachium rosenbergii co-cropping mode, nitrogen fertilizer application is properly reduced in the planting and breeding process, the yield of rice can be guaranteed, meanwhile, the yield of macrobrachium rosenbergii is remarkably increased, and therefore the optimal economic benefits are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of rice field aquaculture, and particularly relates to a rice-Macrobrachium rosenbergii co-cultivation method for reducing nitrogen fertilizer application and increasing efficiency. Background Art

[0002] Integrated rice-fish farming is a typical ecological circular agricultural model. Traditional rice-shrimp farming primarily focuses on Procambarus clarkii. In recent years, factors such as disease outbreaks, concentrated market entry, price fluctuations, and inability to adapt to high temperatures have significantly impacted aquaculture profitability, necessitating the exploration of new models for integrated rice-field farming. Macrobrachium rosenbergii, with its thin shell, plump body, tender meat, and rich nutrition, is characterized by rapid growth, a short breeding cycle, stable prices, and suitability for high-temperature summer cultivation. It has become a promising alternative to Procambarus clarkii in integrated rice-shrimp farming.

[0003] However, the existing technology of rice-Macrobrachium rosenbergii co-cultivation model still has key problems. First, the ratio of nitrogen fertilizer reduction lacks scientific optimization: the amount of nitrogen fertilizer used in rice cultivation needs to be adjusted according to the seasonal type, target yield and production area differences. Generally, 135-195 kg of nitrogen fertilizer (N) is recommended per hectare for indica rice. Most rice-shrimp co-cultivation models still use the nitrogen fertilizer amount of traditional rice cultivation, which can easily lead to rice lodging and reduced yields. In addition, Procambarus clarkii is not resistant to high temperatures, and the actual application area of ​​this model is relatively small. Huang Fei et al. (2022) set 0, 60, 120, 180 and 240 kg / hm 2 The results showed that the optimal nitrogen application rate for rice-shrimp (Procambarus clarkii) transplanting model was 120 kg / hm2. 2 , its output is 8452kg / hm 2 , 120-130kg / hm 2 It can be used as the recommended nitrogen application rate for rice-shrimp co-cultivation system. Xu Qiang et al. (2022) compared the conventional nitrogen application treatment (240 kg / hm2) with the conventional nitrogen application treatment (240 kg / hm2) in the rice-shrimp co-cultivation model. 2 ), the nitrogen reduction treatment (12.5%) reduced yield by 2.9%, increased rice stem bending strength by 13.5%, and reduced lodging index by 1.8%. Peng Chenglin et al. (2020) determined that the optimal nitrogen fertilizer application rate for direct-seeded rice in a long-term rice-shrimp (Procambarus clarkii) co-cultivation model is 102.4 kg / hm2. 2. However, the above research did not involve the yield and survival rate of Procambarus clarkii. Procambarus clarkii (optimal growth temperature is 18-28℃, not resistant to high temperature, and enters the burrowing and summering state when the temperature is too high), and the present invention studies Macrobrachium rosenbergii (optimal growth water temperature is 29-31℃, resistant to high temperature), and the two have different response mechanisms to nitrogen fertilizer-water environment. At present, the rice-Macrobrachium rosenbergii model has not systematically studied the effects of different nitrogen reduction ratios on the survival rate of Macrobrachium rosenbergii and rice yield, making it difficult to achieve a balance between efficient use of nitrogen fertilizer and stable shrimp production. Secondly, the time of rice transplanting and shrimp fry release does not match: the optimal growth temperature of Macrobrachium rosenbergii is 29℃-31℃. Macrobrachium rosenbergii is more sensitive to environmental changes (such as water temperature, dissolved oxygen, and field water depth), and the time of rice transplanting directly affects the field water environment. The existing technology often ignores the coordinated optimization of rice planting time and shrimp fry release time, resulting in a decrease in the survival rate of shrimp fry due to environmental stress (such as high temperature and shallow water), affecting the final yield.

[0004] Therefore, there is an urgent need to explore a breeding method that can achieve both efficient utilization of nitrogen fertilizer and high and stable yield of Macrobrachium rosenbergii. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention sets different nitrogen reduction gradients (100% conventional nitrogen application, 20% reduction, 40% reduction and 60% reduction), and combines the optimized matching of rice transplanting time (early and late) with the time of release of Macrobrachium rosenbergii seedlings to explore its effect on the survival rate and final yield of shrimp seedlings, thereby establishing a "nitrogen fertilizer reduction-rice planting period-shrimp seed release period" coordinated control technology to achieve the efficient utilization of nitrogen fertilizer and the high and stable yield of Macrobrachium rosenbergii.

[0006] The present invention provides a rice-Macrobrachium rosenbergii co-cultivation method for reducing nitrogen fertilizer application and increasing efficiency, comprising the following steps:

[0007] Step S1, treating the paddy field with reduced nitrogen fertilizer: applying all the reduced nitrogen fertilizer urea into the 0-15 cm topsoil of the paddy field, wherein the amount of nitrogen fertilizer after the reduction is 40%-80% of the amount before the reduction;

[0008] Step S2, rice variety and rice seedling transplanting: The rice variety is indica rice, and the rice seedlings are sown and raised in early May each year. The rice seedlings are transplanted to the rice fields after they reach 25-30 days of age;

[0009] Step S3: Stocking Macrobrachium rosenbergii: Stock 45,000 to 90,000 prawns / hm2 on sunny mornings during the rice closure period. 2 The density of the shrimp seedlings was used for breeding;

[0010] Step S4, harvesting: when the water temperature in the paddy field is lower than 20°C, the adult Macrobrachium rosenbergii are harvested and put on the market, and when the rice is mature, the rice is harvested.

[0011] By adopting the above technical scheme, the present invention sets different nitrogen reduction gradients (100% conventional nitrogen application, 20% reduction, 40% reduction and 60% reduction), and combines the optimized matching of rice transplanting time (early and late) with the time of release of Macrobrachium rosenbergii seedlings, to explore its effect on the survival rate and final yield of shrimp seedlings, thereby establishing a "nitrogen fertilizer reduction-rice planting period-shrimp seed release period" coordinated regulation technology, achieving the balance between efficient utilization of nitrogen fertilizer and high and stable yield of Macrobrachium rosenbergii.

[0012] In certain embodiments, in step S1 , the amount of nitrogen fertilizer after the reduction is 40%, 60% or 80% of the amount of nitrogen fertilizer before the reduction, preferably 60%.

[0013] In some embodiments, in step S1, fertilizing further comprises applying phosphorus fertilizer and potassium fertilizer, wherein the phosphorus fertilizer is superphosphate (12.5% ​​P2O5) and the potassium fertilizer is potassium sulfate (57% K2O).

[0014] In some embodiments, in step S1 , the transplanting is performed in wide rows with narrow plants, with a row-plant spacing of 30 cm×20 cm and 2 seedlings per hole.

[0015] In certain embodiments, in step S3, during the rice closure period, the rice leaf area index LAI is ≥5 or the canopy shading rate is ≥80%.

[0016] By adopting the above technical solution, Macrobrachium rosenbergii seedlings are released when the rice rows are closed, the rice leaf area index is ≥5, the shading effect is obvious, and the seedling survival rate is above 95%. Otherwise, in hot weather, direct sunlight and water temperature above 35℃ will affect the survival rate of the shrimp seedlings.

[0017] In some embodiments, in step S3, the morning is before 7 a.m., and the water temperature during the delivery period is ≤31°C.

[0018] In certain embodiments, in step S2, the prawn is fed with a feed according to 2%-4% of the total body weight of the prawn every day for cultivation.

[0019] Compared with the existing technology, the present invention can significantly increase the yield of Macrobrachium rosenbergii by appropriately reducing the application of nitrogen fertilizer (60% CN) in the rice-Macrobrachium rosenbergii co-cultivation model while ensuring rice yield, thereby achieving optimal economic benefits, and at the same time effectively achieving a balance between ecological and economic benefits. At the same time, when the rice rows are closed, Macrobrachium rosenbergii seedlings are released, combined with early rice seedling cultivation and transplanting, that is, when the rice rows are closed in advance, Macrobrachium rosenbergii can be released early, extending the growth cycle of Macrobrachium rosenbergii and improving the cultivation specifications. The rice-Macrobrachium rosenbergii co-cultivation model breeding method of the present invention provides important support for the development of ecological agriculture. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1This is the quadratic regression curve of nitrogen fertilizer application and rice yield in the rice-Macrobrachium rosenbergii model (P<0.05).

[0021] Figure 2 This is the LEfSe analysis diagram of soil microbial communities under different nitrogen reduction levels in the rice-Macrobrachium rosenbergii model.

[0022] Figure 3 The abundance of main metabolic pathways in the KEGG database of soil bacterial communities under different nitrogen reduction levels in the rice-Macrobrachium rosenbergii model. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below with reference to the accompanying drawings and examples. It is particularly noted that if no specific conditions are specified in the following examples, the experiments were carried out according to conventional conditions or the conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following examples can be obtained from common commercial sources.

[0024] Example 1

[0025] A rice-Macrobrachium rosenbergii co-cultivation method for reducing nitrogen fertilizer application and increasing efficiency comprises the following steps:

[0026] Step S1, paddy field nitrogen fertilizer reduction treatment: set conventional nitrogen fertilizer (195kg / hm 2 ), no nitrogen fertilizer (0kg / hm 2 ), 156kg / hm 2 All of the nitrogen fertilizer was applied to the 0-15cm topsoil of the paddy field, that is, the amount of nitrogen fertilizer after the reduction was 80% of the amount before the reduction; at the same time, the amount of phosphorus and potassium applied to rice was 53kg / hm 2 and 105kg / hm 2 , the application types are superphosphate (12.5% ​​P2O5) and potassium sulfate (57% K2O);

[0027] Step S2, transplanting rice seedlings: Rice seedlings are sown and raised in early May each year. When the rice seedlings reach 28 days old, they are transplanted to the field and planted in wide rows with narrow plants, with a row-plant spacing of 30 cm × 20 cm, and two seedlings per hole;

[0028] Step S3, stocking Macrobrachium rosenbergii: stocking shrimp fry at a density of 45,000 to 90,000 before 7:00 a.m. on a sunny day during the rice paddy field closure period (leaf area index LAI ≥ 5 or canopy shading rate ≥ 80%), with the water temperature ≤ 31°C during the stocking period;

[0029] Step S4: When the water temperature in the paddy field is lower than 20° C., the adult Macrobrachium rosenbergii are harvested and marketed; when the rice is mature, the rice is harvested.

[0030] At the same time, water management was implemented: For both the conventional nitrogen fertilizer group and the reduced nitrogen treatment group, water was gradually increased to a depth of 10-15 cm starting one week after the tillering stage. Adjustments were made based on the actual upper limit, maintaining a high water level of 30-40 cm from the jointing stage to 10 days before maturity. The fields were then left idle one week before harvest. Rice was harvested in early October.

[0031] During the culture process of Macrobrachium rosenbergii, 2%-4% of the total body weight of Macrobrachium rosenbergii was fed with a special feed (crude protein content of 38%-42%) twice a day (8:00-9:00 and 17:00-18:00, with a feeding amount of 30% and 70% respectively). The feeding amount of the next day was adjusted according to the feeding situation of each group, and the total feeding amount was 1500-1800 kg / hm2. 2 Aeration facilities are installed in the ring ditch, and oxygenation is maintained from 6:00 PM to 9:00 AM the next day. Aeration is provided throughout the day on rainy days. Adult Macrobrachium rosenbergii are harvested and marketed before October 1st.

[0032] Example 2

[0033] Compared with Example 1, the difference between Example 2 and Example 1 is that the amount of nitrogen fertilizer after the reduction in step S1 is 60% of the amount before the reduction, that is, the amount of fertilizer applied is 117 kg / hm2. 2 , the remaining steps are the same as in Example 1.

[0034] Example 3

[0035] Compared with Example 1, the difference between Example 3 and Example 1 is that the amount of nitrogen fertilizer after the reduction in step S1 is 40% of the amount before the reduction, that is, the amount of fertilizer applied is 78 kg / hm2. 2 , the remaining steps are the same as in Example 1.

[0036] Comparative Example 1

[0037] Compared with Example 2, the difference in the planting and breeding method of Comparative Example 1 is that in step S2, rice is sown and raised in mid-May every year.

[0038] Comparative Example 2

[0039] Compared with Example 2, the difference in the cultivation method of Comparative Example 2 is that the time of releasing Macrobrachium rosenbergii in step S3 is not the rice closure period.

[0040] Effect Examples

[0041] Effect Example 1: Comparison of Seedling Raising Time and Harvest Specifications

[0042] Table 1 Comparison of seedling raising time and harvest specifications

[0043] Seedling raising time Rice planting time Seedling planting time Rice row closure Harvest time Average harvest size May 1 May 30 July 1-15 July 15 September 30 35.66g May 15 June 14 July 15-30 August 1 October 1 26.95g

[0044] As shown in Table 1, based on production experience, water temperatures drop below 20°C after October 1st, affecting the feeding of Macrobrachium rosenbergii. Below 14°C, Macrobrachium rosenbergii will die. Therefore, compared to raising and planting rice seedlings 15-30 days earlier, closing the rice rows earlier in Example 3 allows for earlier stocking of Macrobrachium rosenbergii, extending its growth cycle and improving its growout size.

[0045] Effect Example 2

[0046] Table 2 Comparison of survival rate at seedling stage

[0047] Seedling planting time Leaf area index (LAI) Field surface and ditch water depth Field surface and ditch water temperature Seedling survival rate Non-closed period LAI<5 10-15cm, 1-1.2m 30℃-38℃ 30％-40％ Closure period LAI ≥ 5 30-40cm, 1.2-1.4m 28℃-30℃ 95％

[0048] As shown in Table 2, compared with Comparative Example 2, in Example 3, when Macrobrachium rosenbergii seedlings were released when the rice rows were closed, the rice leaf area index was ≥5, the shading effect was obvious, and the seedling survival rate was above 95%. Otherwise, in hot weather, direct sunlight and water temperature above 35°C would affect the survival rate of the shrimp seedlings.

[0049] Effect Example 3

[0050] Under the rice-M. rosenbergii co-cultivation model, different nitrogen level treatments had significant effects on the physical characteristics of rice stems and leaves (Table 3).

[0051] Table 3 Physical characteristics of rice stems and leaves under different nitrogen levels in the rice-Macrobrachium rosenbergii model

[0052]

[0053] Table 3 shows that plant height decreased with decreasing nitrogen application rate. There were no significant differences between the 80% CN and 60% CN treatments and the CK, while the 40% CN treatment was significantly lower than the CK. Regarding biomass allocation, leaf dry weight in the 40% CN treatment was significantly lower than the CK and other treatments. Stem dry weight in the 80% CN treatment was significantly higher than in the 40% CN treatment (P < 0.05), but not significantly different from the CK and 60% CN treatments. Leaf SPAD values ​​decreased with decreasing nitrogen application rate, with only the 40% CN treatment significantly lower than the CK. Regarding yield traits, ear length and ear weight in the 40% CN treatment were significantly higher than in the 80% CN treatment, with no significant differences between the 80% CN and 60% CN treatments and the CK. With decreasing nitrogen application rate, plant height and leaf SPAD values ​​decreased, while leaf weight and stem weight initially increased and then decreased, and ear length and ear weight initially decreased and then increased. Lodging was most severe in the CK, followed by the 80% CN treatment. The 60% CN and 40% CN treatments did not experience lodging.

[0054] Effect Example 4

[0055] The rice yield and yield components under different nitrogen reduction levels of the Macrobrachium rosenbergii model were tested, and the results are shown in Table 4.

[0056] Table 4 Rice yield and yield components under different nitrogen reduction levels in the rice-Macrobrachium rosenbergii model

[0057]

[0058] As can be seen, rice yield initially increased and then decreased with decreasing nitrogen application rates. Yield was highest when nitrogen application was 80% of the conventional nitrogen rate (CN), but the difference from 60% CN and CK was not significant. The 40% CN treatment group had the lowest yield, significantly lower than 80% CN, 60% CN, and CK. Regarding yield composition, tiller number initially increased and then decreased, with the 80% CN treatment producing the most tillers, significantly higher than 60% CN and 40% CN, but not significantly different from CK. Seed set rate increased with increasing nitrogen reduction, with no significant difference between 80% CN and CK, but significantly higher than CK in 60% CN and 40% CN treatments. 1000-grain weight (26.10g-26.60g) did not differ significantly among treatments (P>0.05).

[0059] Effect Example 5

[0060] The nitrogen fertilizer application rate and rice yield of the rice-Macrobrachium rosenbergii model were measured. The results are as follows: Figure 1 As shown in the figure, the regression analysis of rice yield (y) and nitrogen fertilizer application (x) showed that the two showed a significant quadratic function relationship (P<0.05). The adjusted determination coefficient (R adj 2 =0.9961) indicates that nitrogen fertilizer application rate can explain 99.61% of the variation in rice yield, and the fitting effect is good. The quadratic term coefficient is negative (-0.0936), indicating that rice yield increases first and then decreases with increasing nitrogen fertilizer application rate. Calculations show that when nitrogen fertilizer application rate is 167.08 kg / hm2, 2 When the rice yield reaches the theoretical maximum of 8044.66 kg / hm 2 .

[0061] Effect Example 6

[0062] The yield and yield components of Macrobrachium rosenbergii under different nitrogen reduction levels in the rice-Macrobrachium rosenbergii model were analyzed, and the results are shown in Table 5.

[0063] Table 5 Macrobrachium rosenbergii yield and yield components under different nitrogen reduction levels in the rice-Macrobrachium rosenbergii model

[0064]

[0065] Analysis revealed that the survival rate of Macrobrachium rosenbergii under conventional nitrogen fertilizer (CK) was significantly lower than that of the reduced nitrogen fertilizer treatments (P < 0.05). The weight gain and specific growth rate of the 60% CN group were significantly higher than those of the CK group, while the feed conversion ratio (FCR) (1.15) was significantly lower than that of the CK group. The average weight of Macrobrachium rosenbergii under the reduced nitrogen fertilizer (CK) group did not differ significantly from that of the CK group. In terms of yield, the 60% CN group significantly increased by 12.73% compared to the CK group (P < 0.05), with no significant differences among the reduced nitrogen fertilizer treatments.

[0066] Effect Example 7

[0067] The effects of nitrogen fertilizer reduction on soil nutrients and physical and chemical properties under the rice-Macrobrachium rosenbergii model were analyzed, and the results are shown in Table 6.

[0068] Table 6 Soil physical and chemical properties and nutrient contents under different nitrogen reduction levels in the rice-Macrobrachium rosenbergii model

[0069]

[0070] The data in Table 6 indicate that the different nitrogen reduction treatments had a certain impact on soil physical and chemical properties and nutrient content. pH increased with increasing nitrogen reduction ratios, with no significant differences among the three treatments. The 40% CN treatment had a significantly higher pH than the CK treatment (P < 0.05). Soil bulk density reached its lowest value in the 80% CN treatment and was significantly lower than that in the 60% CN treatment (P < 0.05). Total nitrogen content did not differ significantly among treatments, and organic matter content remained stable. Ammonia nitrogen content decreased significantly with increasing nitrogen reduction ratios, with no significant differences between 60% CN and 40% CN. Nitrate nitrogen, available phosphorus, and available potassium content did not show significant differences among treatments.

[0071] Effect Example 8

[0072] The effects of nitrogen fertilizer reduction on soil microbial community characteristics in the rice-Macrobrachium rosenbergii model were studied, and the results are shown in Table 7.

[0073] Table 7 α-diversity of soil bacterial communities under different nitrogen reduction levels in the rice-Macrobrachium rosenbergii model

[0074]

[0075] Compared with the CK, nitrogen reduction treatment had no significant effect on the Chao1 index and Shannon index of the soil bacterial community (Table 7), indicating that short-term nitrogen reduction did not significantly alter the species richness of the microbial community. The Shannon index of the 40% CN treatment was significantly higher than that of the CK, while the Shannon index of the 80% CN and 60% CN treatments did not differ significantly from that of the CK, but showed an upward trend. The Simpson index showed that all nitrogen reduction treatments were significantly higher than that of the CK.

[0076] Effect Example 9

[0077] The results of LEfSe analysis of soil microbial communities under different nitrogen reduction levels in the rice-Macrobrachium rosenbergii model are as follows: Figure 2 shown.

[0078] Under different nitrogen reduction treatments, soil bacterial communities showed significant taxonomic group-specific responses. Latescibacterota (class / phylum / order / genus) was significantly enriched under 60% CN, while Longimicrobiales-related groups (o__Longimicrobiales, f__Longimicrobiaceae) were prominent in the 40% CN treatment. Ellin6067 (Chloroflexi) was also highly abundant under 40% CN. The 80% CN treatment was characterized by candidate group P2_11E (order / family / class / genus) and the genus Longispora. Under CK (100% CN), multiple functional bacterial genera were significantly enriched, including Micromonospora, Pedobacter, Agromyces, Paenisporosarcina, Caulobacter, and Fictibacillus. Tepidibacillus was prominent in the 60% CN treatment, while Fictibacillus was highly abundant under 100% CN. These results indicate that different nitrogen reduction intensities selectively shaped specific microbial community structures, with low nitrogen conditions (40%-60% CN) tending to enrich oligotrophic and parasitic groups, while high nitrogen treatment (100% CN) favored the growth of aerobic heterotrophic bacteria.

[0079] As shown, nitrogen reduction treatments significantly altered soil bacterial community structure, with different nitrogen levels selectively enriching microbial groups with specific ecological strategies. Nitrogen availability is a key environmental factor driving soil microbial community assembly, as evidenced by the following: low nitrogen conditions (40%-60% CN) selectively enriched oligotrophic microorganisms (such as the Longimicrobiales order) and parasitic / commensal microorganisms (such as the Latescibacterota family), while high nitrogen conditions (100% CN) favored the growth of aerobic heterotrophs (such as Micromonospora and Pedobacter). The differential enrichment of candidate groups (such as P2_11E and Ellin6067) across treatments suggests that soil "microbial dark matter" may play an important, yet as yet unidentified, ecological role in nitrogen cycling.

[0080] Effect Example 10

[0081] The abundance of the main metabolic pathways in the KEGG database of soil bacterial communities under different nitrogen reduction levels in the rice-Macrobrachium rosenbergii model was analyzed. Figure 3 shown.

[0082] The abundance of metabolic pathways in paddy soil bacterial communities varied under different nitrogen fertilizer treatments. Comparisons between the conventional nitrogen fertilizer (CK) and reduced nitrogen fertilizer (80%-40% CN) treatments revealed that amino acid metabolism, carbohydrate metabolism, and energy metabolism pathways were generally elevated in the reduced nitrogen treatments. The 80% CN group exhibited the highest abundance of amino acid metabolism, increasing by approximately 7.6% compared to the CK average. Among secondary metabolite synthesis pathways, terpenoid and polyketide metabolism were significantly enhanced under reduced nitrogen conditions, with abundance increasing by 19.5% in the 80% CN group compared to the CK. Cofactor and vitamin metabolism, as well as nucleotide metabolism, also showed higher abundance levels under the reduced nitrogen treatment. However, lipid metabolism, other amino acid metabolism, and xenobiotic degradation pathways showed no significant differences among the different nitrogen fertilizer treatments. The abundance of lipid metabolism remained within a range of 2419.89-2644.77 across all treatments. The abundance of carbohydrate biosynthesis and metabolism pathways increased under reduced nitrogen conditions, with abundance increasing by 17.1% in the 80% CN group compared to the CK. These data indicate that nitrogen reduction treatment significantly affected the basal metabolic activities of soil bacterial communities, especially the metabolic pathways related to carbon and nitrogen transformation.

[0083] It can be seen that nitrogen reduction treatment significantly increased the abundance of metabolic pathways related to carbon and nitrogen transformation (such as amino acids, carbohydrates, energy metabolism and secondary metabolite synthesis) in paddy field soil bacterial communities, indicating that nitrogen reduction fertilization can promote the metabolic activity of soil microorganisms.

[0084] Effect Example 11

[0085] The effects of nitrogen fertilizer reduction on the physical and chemical properties of water under the rice-Macrobrachium rosenbergii model were studied, and the results are shown in Table 8.

[0086] Table 8 Physicochemical properties of water under different nitrogen reduction levels in the rice-Macrobrachium rosenbergii model

[0087]

[0088] In the rice-Macrobrachium rosenbergii co-cultivation model, by comparing the effects of different nitrogen application levels (CK, 80% CN, 60% CN, 40% CN) on the physical and chemical properties of the water body, the study found that under the condition of maintaining the same stocking density and feed amount of Macrobrachium rosenbergii, reducing the amount of nitrogen fertilizer applied can significantly improve the water quality environment. With the increase in the nitrogen reduction ratio, the concentrations of total nitrogen, total phosphorus, ammonia nitrogen and nitrite nitrogen in the water body all decreased significantly, among which the 40% CN treatment had the most obvious effect, with total nitrogen decreasing from 2.49 mg / L in the control group to 1.26 mg / L, and total phosphorus decreasing from 0.29 mg / L to 0.12 mg / L. At the same time, the permanganate index (COD Mn) and chlorophyll a (Chl a) content also decreased significantly, indicating that nitrogen reduction effectively reduced organic pollution and inhibited excessive algal growth, thereby improving water transparency. The eutrophication index (TLI) of each group was in the mesotrophic level range of 30-50, indicating that the water bodies of each treatment group did not reach eutrophication. It is worth noting that with the increase in the nitrogen reduction ratio, the TLI value showed a significant downward trend, among which the 40% CN treatment group had the lowest TLI value (39.39), which was closest to the oligotrophic state threshold (TLI < 30). Although the TLI value of the conventional fertilization group (45.94) was still in the mesotrophic range, it was close to the eutrophication critical value (50) and there was a potential eutrophication risk. In addition, the nitrogen reduction treatment did not cause the pH value to exceed the suitable range of Macrobrachium rosenbergii (7.0-8.5), indicating that it had no negative impact on the aquaculture environment.

[0089] Overall, in the rice-Macrobrachium rosenbergii co-cultivation system, even if the same stocking density and feed amount are maintained, reducing nitrogen fertilizer application by 40% can still significantly optimize water quality and reduce the risk of eutrophication without adversely affecting shrimp survival.

[0090] Effect Example 12

[0091] The effect of nitrogen fertilizer reduction on the economic benefits of the rice-Macrobrachium rosenbergii model was analyzed, and the results are shown in Table 9.

[0092] Table 9 Benefits of rice-Macrobrachium rosenbergii model under different nitrogen reduction levels

[0093] project CK 80% CN 60% CN 40% CN Pond rental (yuan / mu) 700 700 700 700 Rice transplanting cost (yuan / mu) 200 200 200 200 Labor cost (yuan / mu) 300 300 300 300 Rice cost (yuan / mu) 1500 1500 1500 1500 Seedling unit price (yuan / kg) 76 76 76 76 Seedling quantity (kg / mu) 24 24 24 24 Seedling cost (yuan / mu) 1824 1824 1824 1824 Feed quantity (kg / mu) 150 150 150 150 Feed cost (yuan / mu) 1800 1800 1800 1800 N fertilizer (kg / mu) 13 10.4 7.8 5.2 N fertilizer cost (yuan / mu) 46.8 37.44 28.08 18.72 Cost of phosphate fertilizer and potash fertilizer (yuan / mu) 50 50 50 50 Electricity fee (yuan / mu) 200 200 200 200 Rice harvest (yuan / mu) 80 80 80 80 Total cost (yuan / mu) 6883.8 6871.84 6859.88 6847.92 Rice yield per mu (kg / mu) 531.52 535.31 520.67 486.18 Rice price (yuan / kg) 3.6 3.6 3.6 3.6 Rice income (yuan / mu) 1913.47 1927.1 1874.42 1750.26 Shrimp production (kg / mu) 122.47 133.02 138.05 131.8 Price (yuan / kg) 80 80 80 80 Macrobrachium rosenbergii income (yuan / mu) 9797.28 10641.6 11044.05 10544.05 Total income (yuan / mu) 11710.75 12568.7 12918.47 12294.31 Benefit per mu (yuan / mu) 4826.95 5696.86 6058.59 5446.39

[0094] This experiment compared the effects of different nitrogen application levels (CK, 80% CN, 60% CN, and 40% CN) on the economic benefits of a rice-M. rosenbergii co-cultivation model. In terms of cost structure, fixed costs (such as pond rental, transplanting costs, labor costs, and feed costs) remained consistent across treatment groups, while nitrogen fertilizer costs gradually decreased as the nitrogen reduction ratio increased, from 46.8 yuan / mu (13 kg / mu) in the control group to 18.72 yuan / mu (5.2 kg / mu) in the 40% CN group. Due to the relatively small proportion of nitrogen fertilizer costs, the difference in total costs was not significant. The 40% CN group had the lowest total cost (6,847.92 yuan / mu), only 35.88 yuan / mu less than the control group (6,883.8 yuan / mu).

[0095] In terms of income, rice yield decreased with increasing nitrogen reduction rates, from 531.52 kg / mu in the control group to 486.18 kg / mu in the 40% CN group, resulting in a corresponding decrease in rice income. However, Macrobrachium rosenbergii yield peaked in the 60% CN group (138.05 kg / mu), a 12.7% increase over the control group (122.47 kg / mu), and shrimp income also increased accordingly. Overall, the 60% CN group had the highest total income (12,918.47 yuan / mu), with a per-mu benefit of 6,058.59 yuan / mu, a 25.5% increase over the control group (4,826.95 yuan / mu). The per-mu benefits of the 80% CN and 40% CN groups were 5,696.86 yuan / mu and 5,446.39 yuan / mu, respectively, both exceeding the control group but lower than the 60% CN group.

[0096] In summary, in the rice-M. rosenbergii co-culture model, appropriately reducing nitrogen fertilizer application (60% CN) can significantly increase M. rosenbergii yield while maintaining rice yield, thereby achieving optimal economic benefits. Although the 40% CN group had the lowest nitrogen fertilizer cost, due to the significant reduction in rice yield, it did not meet the requirement of "Technical Specifications for Integrated Rice-Fish Farming Part 1: General Principles" that rice yield in plain areas should not be less than 7500 kg / hm2. 2 Therefore, from an economic perspective, a nitrogen fertilizer application level of 60% CN is recommended to achieve a balance between ecological and economic benefits.

[0097] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed. However, as long as such modifications are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A rice-Macrobrachium rosenbergii co-cultivation method for reducing nitrogen fertilizer application and increasing efficiency, characterized in that: The following steps are included: Step S1, treating the paddy field with reduced nitrogen fertilizer: applying all the reduced nitrogen fertilizer urea into the 0-15 cm topsoil of the paddy field, wherein the amount of nitrogen fertilizer after the reduction is 40%-80% of the amount before the reduction; Step S2, rice variety and rice seedling transplanting: The rice variety is indica rice, and the rice seedlings are sown and raised in early May each year. The rice seedlings are transplanted to the rice fields after they reach 25-30 days of age; Step S3: Stocking Macrobrachium rosenbergii: Stock 45,000 to 90,000 prawns / hm2 on sunny mornings during the rice closure period. 2 The density of the shrimp seedlings was used for breeding; Step S4, harvesting: when the water temperature in the paddy field is lower than 20°C, the adult Macrobrachium rosenbergii are harvested and put on the market, and when the rice is mature, the rice is harvested.

2. The method for growing and breeding according to claim 1, wherein: In step S1, the amount of nitrogen fertilizer after the reduction is 40%, 60% or 80% of the amount of nitrogen fertilizer before the reduction, preferably 40%.

3. The planting and breeding method according to claim 1, characterized in that In step S1, fertilizing further includes applying phosphorus fertilizer and potash fertilizer, wherein the phosphorus fertilizer is superphosphate and the potash fertilizer is potassium sulfate.

4. The planting and breeding method according to claim 1, characterized in that In step S1, the transplanting is performed in wide rows and wide spacing, with a row-plant spacing of 30 cm×20 cm and 2 seedlings per hole.

5. The planting and breeding method according to claim 1, characterized in that: In step S3, during the rice closure period, the rice leaf area index LAI is ≥5 or the canopy shading rate is ≥80%.

6. The planting and breeding method according to claim 1, characterized in that: In step S3, the morning is before 7 a.m., and the water temperature during the delivery is ≤ 31°C.

7. The planting and breeding method according to claim 1, characterized in that: In step S2, the Macrobrachium rosenbergii is fed with feed according to 2%-4% of the total body weight every day for cultivation.

Images