Effects Of Returning Rice Straw To The Field On Soil Nutrients And Rice Yield In Cold Regions

The Northeast region is an important rice production base in China.In 2021,the planting area was 53.804 thousand hectares,and the rice yield was 41.383 million tons.According to the grain straw ratio of 1:1.2,the amount of rice straw reached 49.660 million tons.A large amount of leftover straw is burned in the open air,which is an important source of atmospheric pollution in Northeast China after autumn harvest and before spring sowing.Direct returning to the field can solve the problems of resource waste and environmental pollution caused by the serious surplus of straw.At the same time,it can return the nutrient elements in the straw to the soil,improve the soil structure and physical and chemical properties,and increase the supply of soil nutrients.It is the long-term nutrient source of farmland and the most direct method to solve the serious surplus of rice straw in Northeast China.Reasonable straw returning to the field can compensate for potential soil fertility consumption,accumulate nitrogen,activate phosphorus,and return potassium,achieving sustainable agricultural development.It can also improve crop yield and increase nutrient absorption and accumulation.In order to deeply explore the impact of straw returning on soil nutrients and rice yield in the black soil area of Northeast China,Longdao 21 was used as the experimental material and conducted at the Xiangyang Experimental Internship Base of Northeast Agricultural University in2021.Through a long-term（≥10 years）positioning experiment in the community,rice straw not returning to the field（S0）,straw low returning to the field（CL）,and straw high returning to the field（CH）were set up There are six treatments:high yield return of straw every two years（IH）,high yield return of straw every two years（IH2）,and abandonment（AL）.During the maturity period of rice,samples of 0-15cm topsoil and rice plants were collected for analysis to clarify the impact of returning rice straw to the field on soil nutrients and rice yield in the cold region.This provides theoretical basis and reference for analyzing the fertilization effect of returning rice straw to the field on soil and the contribution of rice nutrients and yield in the Northeast cold region.The test results indicate that:（1）Returning rice straw to the field for 14 consecutive years can significantly increase soil nitrogen content.Long term straw returning significantly increased the content of total nitrogen,NH4⁺-N,and NO3^--N.Returning rice straw significantly increased the content of soil acid hydrolyzed total nitrogen,acid hydrolyzed ammonium nitrogen,acid hydrolyzed amino acid nitrogen,and non acid hydrolyzed nitrogen,but had no significant effect on soil acid hydrolyzed amino sugar nitrogen and acid hydrolyzed unknown nitrogen.Returning rice straw to the field increased the proportion of acid hydrolyzed ammonium nitrogen and amino acid ammonia in the acid hydrolyzed nitrogen,but had no significant effect on the proportion of acid hydrolyzed amino sugar nitrogen and unknown acid hydrolyzed nitrogen.（2）Returning straw to the field can significantly increase soil phosphorus content.Long term return of rice straw significantly increases the content of total phosphorus and available phosphorus in the soil.Returning rice straw to the field in cold regions significantly increased the content of Na HCO₃-Pi,Na HCO₃-Po,Na OH-Pi,Na OH-Po and HCl-P in the soil,while the content of H₂O-P and Residual-P in the soil did not reach a significant difference level among different treatments.（3）Returning straw to the field can significantly increase soil potassium content.Long term straw returning significantly increased the total potassium and available potassium content in the soil.The continuous high amount of straw returning to the field treatment showed the most significant improvement in soil potassium content.（4）Returning straw to the field can significantly increase soil organic carbon content.The continuous high-yield straw returning treatment had the greatest increase in soil organic carbon content.（5）Returning rice straw to the field increased the nitrogen content in rice roots,but did not have a significant impact on the nitrogen content in stems,leaves,and grains.Returning rice straw to the field can increase the phosphorus content in rice roots and stems,but has no significant impact on the phosphorus content in leaves and grains.Returning straw to the field can increase the potassium content in rice roots,stems,leaves,and grains to varying degrees.Compared with the non returning treatment,continuous long-term high-yield rice straw returning can increase the accumulation of nitrogen,phosphorus,and potassium in the entire plant of rice.（6）Returning straw to the field increased the number of grains per panicle,thousand grain weight,and seed setting rate.Through analysis of rice yield for many consecutive years,it was found that the straw returning treatment had a trend of increasing rice yield compared to the straw not returning treatment,but did not reach a significant level of difference.