Effects Of Increasing Density And Reducing Nitrogen On Annual Rice And Wheat Yield And Soil Fertility In Rice Areas Along The Yellow River

In order to solve the problems of tight growing season,insufficient soil fertility,and low fertilizer utilization efficiency in the rice-wheat double-cropping cultivation mode in the rice areas along the Yellow River,combined with the country’s vigorously promoted measures of returning straw to the field,this experiment is based on field experiments.Through the integration of rice-wheat double-cropping high-yield and efficiency-increasing farming and cultivation techniques in the Yellow River rice area,it provides theoretical basis and technical support for achieving high-yield and increased efficiency under the condition of rice-wheat double-cropping in the Yellow River rice area.This experiment designed 4 treatments: straw return to field,rice-wheat rotary tillage,conventional density,conventional water and fertilizer(T1);straw return to field,rice-wheat rotary tillage,conventional density,conventional water and fertilizer(T2);straw return to field,rice Seasonal rotary tillage,wheat season no-tillage(intercropping),increase density and reduce nitrogen(base fertilizer and ear fertilizer are reduced by 10%)(T3);return straw to the field,rice season rotary tillage,wheat season no-tillage(stripe seeding),increase density Nitrogen reduction(10% reduction in base fertilizer and ear fertilizer)(T4).Research indicates:1.Under the condition of returning straw to the field to increase density and reduce nitrogen combined with no-tillage treatment in wheat season can increase the yield of rice and wheat.Compared with the two years of T1,the yield of the rice season under the optimized mode T3 increased by 9.34% and 23.5%,respectively,compared with 4.43% and 11.96% for T2,and 3.78%for the second year compared with T4.The increase in rice yield is mainly manifested in increasing the thousand-grain weight.Compared with the T1 treatment,the increase of the thousand-grain weight in the two years reached a significant level,increasing by 4.62% and 3.81%,respectively,compared with the T2 treatment by 0.54% and 8.21%.The thousand-grain weight of T3 treatment in the second rice season increased by 5.36% compared with T4.Compared with the other three treatments,there was an increase in wheat yield T3,and the increase was 35.34%,28.51%,and 28.29% respectively;the increase in wheat yield was mainly manifested in the increase in the number of effective ears,and the increase was 25.32%,respectively,with the other three treatments.15.55% and 12.26%.2.Density increase and nitrogen reduction treatment under the condition of returning straw to the field can significantly increase the accumulation of dry matter above the ground and increase the population growth after anthesis.Combined with no-tillage in the wheat season,it can increase the accumulation of dry matter above the ground and the population growth after anthesis.Whether it is wheat or rice seasons,the stems,leaves,and sheaths of T3 are significantly higher than T1 and T2 at the heading,flowering and maturity stage,and the population growth after flowering is significantly higher than that of T1;compared to T4,T3 can significantly increase wheat There was no significant difference in stem dry matter weight during maturity and flowering stage,dry matter weight of ear and leaf at mature stage,and dry matter weight of leaf and ear at flowering stage,but T3 was higher than T4,and population growth quality after T3 was both Higher than the other 3 treatments.3.Density increase and nitrogen reduction treatment under the condition of returning straw to the field can significantly increase the nutrient accumulation of the above-ground plants in the wheat and rice seasons.The nitrogen,phosphorus and potassium contents of the aboveground plants of T3 in the two-year rice season were significantly higher than those of T1 and T2 in the two key growth periods.The nitrogen and potassium content in the shoots of T3 in the wheat season were higher than those of the other three treatments,and there was no significant difference in the phosphorus content between the two key growth periods and the other three treatments.The nitrogen harvest index is increasing year by year.In 2020,the T3 nitrogen harvest index will increase significantly compared with T1 and T2.The partial nitrogen productivity of T3 in rice and wheat seasons was significantly higher than that of T1 and T2,compared with T4,but higher than T4.4.Densification and nitrogen reduction treatment under the condition of returning straw to the field can significantly increase the p H,organic matter,available potassium,and available phosphorus content of the top soil(0-10cm).The p H of the surface soil(0-10cm)of T3 was significantly higher than that of T1 after the rice harvest,indicating that returning straw to the field can significantly increase the p H of the surface soil.The organic matter in the surface soil(0-10cm)of T3 is higher than that of T1 and T2 after the harvest of rice and wheat,indicating that increasing the density and reducing nitrogen under the condition of returning straw to the field can increase the content of organic matter in the surface soil.Different treatments did not significantly change the total nitrogen content in the soil.The content of available potassium and available phosphorus of T3 surface soil(0-10cm)were higher than those of T1 and T2 after rice harvest and wheat harvest.5.Densification and nitrogen reduction treatment under the condition of returning straw to the field can significantly reduce the surface water nitrogen and phosphorus content of the rice season,and can reduce the global warming potential and greenhouse gas intensity of the rice field.Most of the paddy field surface water under each treatment peaked before and after the application of fertilizer.In 2019,the content of nitrite nitrogen,ammonium nitrogen,and soluble phosphorus in the paddy field surface water after the straw return treatment(T2,T3)was significantly higher than that of the straw Treatment without returning to the field(T1),and returning straw to the field to increase density and reduce nitrogen(T3)can significantly reduce the nitrogen and phosphorus content in the paddy field surface water compared with conventional tillage(T2),thereby reducing the loss of nitrogen and phosphorus in surface runoff water.In 2020,the content of nitrite nitrogen and soluble phosphorus in the surface water of T3 rice fields are lower than those of the other three treatments,and the content of ammonium nitrogen in the water of T3 rice fields is at a higher level,which may be due to the promotion of returning straw to the field for two years.The volatilization of ammonia in the paddy field.T3 rice field methane,nitrous oxide,GWP and GHGI are all at high levels,but combining the two-year results,the methane emissions of T3 in the first year are significantly higher than that of conventional treatment without straw return(T1)and straw return.Field conventional treatment(T2),but the methane emission under T3 treatment in the second year is no longer significantly different from T2 treatment.The same is true for GWP and GHGI.The nitrous oxide emissions of T3 in the first year are significantly lower than that of straw not returning to the field.The conventional treatment T1 and the conventional treatment T2 of straw returning to the field increased somewhat in the second year,but their influence on the warming potential was less than that of methane.In summary,the treatment of densification and nitrogen reduction under straw returning to the field combined with no-tillage in wheat season(T3)can alleviate the problem of the tight growing season of the rice-wheat dual cropping mode,and significantly increase the accumulation of nutrients and nitrogen in the above-ground plants of rice and wheat.The harvest index and nitrogen partial productivity increase the dry matter accumulation above the ground and the growth quality of the population after anthesis,and finally increase the yield of rice and wheat,which are mainly manifested in the thousand-grain weight and the number of effective ears,respectively.At the same time,T3 can ensure the increase of soil p H,organic matter,available potassium,and available phosphorus content,thereby providing a better living environment for plants.Regarding the paddy field environment,T3 can significantly reduce the loss of nitrogen and phosphorus in surface runoff water caused by the return of straw to the field,and in the long run can reduce the methane emissions of the paddy field,thereby reducing the global warming potential of the paddy field and the intensity of greenhouse gases.