| The rice-crayfish coculture(RC)is a rice farming mode with the largest area and the highest total yield in China,which has good scientific research value.As two important agricultural measures of rice-crayfish coculture,straw return and crayfish feeding are bound to cause a series of effects on soil physical and chemical properties,and these effects are not clear,and scientific research is urgently needed.To this end,this study used 8 years(starting in 2015)straw return to the field feeding long-term positioning experiment,the experimental treatments were: RC with straw returning and feeding(SF),RC with straw returning and no feeding(SNF),RC with no straw returning and feeding(NSF),RC with no straw returning and no feeding(NSNF),RM with straw returning(CK-S),RM with no straw returning(CK-NS),Exploring the effects of rice and crayfish coculture and feeding on the soil physicochemical properties of rice paddy can help us better understand the influence of rice and crayfish patterns on land,and provide a theoretical basis for improving and regulating rice and crayfish patterns.The main results are as follows:1.Changes in rice and crayfish yields:The average yield in the 7-year period was compared,and the rice monocropping in the early stage was 18.81% higher than that of rice-crayfish,and the rice-crayfish in the later stage was 16.44% higher than that in the later stage of rice planting,the yield of straw returned to the field was 2.57% higher than that of straw not returned to the field,and feeding had no significant effect on the rice yield.The yield of crayfish increased by47.17%,and the return of straw to the field increased by 13.50%.2.Long-term dynamic changes of soil physicochemical properties in paddy fields :The long-term change trend showed that in the rice-crayfish coculture mode,ammonium nitrogen,total kalium and Eh showed an increasing trend,alkaline hydrolyzable nitrogen and available kalium effect showed a decreasing trend,organic matter and nitrate nitrogen showed a trend of first decreasing and then increasing,total nitrogen and p H showed a trend of first increasing and then decreasing and increasing,while total phosphorus and available kalium showed no obvious change trend.Multi-year maturation results are compared on average.Indicate: Compared with the rice monocroppingl,Eh,organic matter,total nitrogen,ammonium nitrogen,nitrate nitrogen and alkaline hydrolyzable nitrogen increased by 38.18%,14.35%,6.38%,9.33%,12.42% and 14.19%,and p H and available kalium decreased by 3.35% and 5.51%respectively.Compared with the straw not returned to the field,the Eh,organic matter,total nitrogen,ammonium nitrogen,alkaline hydrolyzable nitrogen,total phosphorus,total kalium and available kalium increased by 14.00%,6.8%,2.54%,23.91%,4.35%,3.42%,3.55% and 0.28%,and the p H,nitrate nitrogen and available phosphorus decreased by3.12%,11.12% and 9.17% respectively.Compared with no feeding,organic matter,total nitrogen,ammonium nitrogen,total phosphorus,available phosphorus and available kalium increased by 2.29%,1.67%,3.10%,3.78%,7.11% and 2.30%,respectively,and nitrate nitrogen decreased by 10.10%.Other treatments and physicochemical properties did not show differences.Compared with the pre-test(2015),the ammonium nitrogen,nitrate nitrogen,total kalium,p H and Eh cocropping of rice-caryfish in 2022 increased by 260.35%,25.26%,55.82%,4.84% and 94.39% respectively,and total nitrogen,alkaline hydrolyzable nitrogen,total phosphorus,available phosphorus and available kalium decreased by10.70%,11.21%,4.35%,35.31% and 8.31% respectively,and the organic matter changed significantly.3.The impact of soil physicochemical properties of paddy fields in 2022 :In 2022,the soil of winter flooded period,seedling period,tillering period,full-heading period and maturity period was analyzed,Ph and Eh of rice-crayfish coculture showed an increasing trend,organic matter,total nitrogen,alkaline hydrolyzable nitrogen,total phosphorus and available kalium showed an increasing trend after increase,ammonium nitrogen and nitrate nitrogen showed a decreasing trend after reduction,and available phosphorus had no change trend.At maturity,compared with the rice monocropping,the organic matter,ammonium nitrogen,alkaline hydrolyzable nitrogen,available phosphorus,total kalium and Eh of rice-crayfish coculture increased by 5.47%,28.14%,4.93%,4.35%,2.27% and 21.44%respectively,and the total nitrogen,nitrate nitrogen,total phosphorus,available kalium and p H decreased by 3.53%,14.28%,4.30%,7.79% and 3.65% respectively.Compared with the straw not returned to the field,the organic matter,total nitrogen,ammonium nitrogen,nitrate nitrogen,alkaline hydrolyzable nitrogen and available kalium increased by 7.94%,5.97%,5.95%,24.32%,7.50% and 1.99% respectively,and the total phosphorus,available phosphorus,total kalium,p H and Eh decreased by 3.56%,7.98%,2.29%,5.51% and 8.48% respectively.Compared with no feeding,total nitrogen,total phosphorus and available phosphorus increased by 8.31%,8.11% and 14.77%respectively,and ammonium nitrogen and nitrate nitrogen decreased by 7.99% and40.68%,respectively,and the effect of feeding on other indexes was not obvious.4.The correlation analysis of soil physical and chemical indexes:There were different correlations between different soil physicochemical indexes,including significant or very significant positive correlation between Eh and total nitrogen,nitrate nitrogen,alkaline hydrolyzable nitrogen,significant or very significant negative correlation between p H and total nitrogen,alkaline hydrolyzable nitrogen,significant or very significant correlation between organic matter and Eh,ammonium nitrogen,nitrate nitrogen,available nitrogen,alkaline hydrolyzable nitrogen,available phosphorus,total kalium,and a very significant positive correlation between total nitrogen and alkaline hydrolyzable nitrogen,between ammonium nitrogen and available nitrogen,nitrate nitrogen and available nitrogen,total kalium respectively.In addition,there was a significant positive correlation between available nitrogen and total kalium,a significant negative correlation between alkaline hydrolyzable nitrogen and available phosphorus,a significant correlation between total phosphorus and available phosphorus,total kalium,and no correlation between available potassium and other soil physical and chemical indexes.During the redundancy analysis,it can be seen that total kalium,p H,nitrate nitrogen,organic matter and total phosphorus have significant effects on the theoretical yield constituent factors of rice,and total phosphorus and total kalium have significant effects on the actual yield of rice.The analysis of soil fertility by principal component analysis showed that compared with the rice monocropping,rice-crayfish coculture could improve soil fertility,and in rice-crayfish coculture,straw returning to the field could improve soil fertility compared with straw not returning to the field,but the effect of feeding on soil fertility was not obvious.In summary,straw return can significantly improve the soil physicochemical properties of rice-crayfish models,improve soil fertility and increase rice yield.The physicochemical properties and fertility of the soil were not obvious,which significantly increased the yield of crayfish.Rice-crayfish coculture did not significantly promote phosphorus and potassium,while redundancy analysis showed that phosphorus and potassium had a significant effect on rice yield in rice-crayfish coculture,because straw returning to the field could supplement potassium,and it was recommended that fertilizer increase phosphorus. |
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