Emission Characteristics of Organic Carbon and Nitrogen and Phosphorus from Rice Fields under Different Straw and Nitrogen Fertilizers Input
In order to understand the impact of reducing nitrogen fertilizer input under straw application on the emission characteristics of organic carbon,nitrogen and phosphorus in paddy fields,and to provide technical support for the optimi-zation of input application and nutrient management in paddy fields,pot experiment was conducted to study the effects of wheat straw return and fertilizer application on the concentrations of organic carbon,nitrogen and phosphorus in surface water of rice field with silt soil and clay soil,as well as on their potential emissions and on rice yield.The results indicate that the risk of nutrient emissions from surface runoff in silt soil was much higher than that in clay soil,with the basal fer-tilizer period being more pronounced;Phosphorus had the highest emission risk in the field runoff during the basal fertilizer period,organic carbon treated with straw had the highest emission risk in the field runoff during the tillering fertilizer peri-od,and nitrogen had the highest emission risk during the panicle fertilizer period.Regardless of whether it was in silt soil or clay soil,on the basis of straw application,compared to applying constant nitrogen fertilizer,applying a small amount of nitrogen fertilizer could effectively reduce the risk of nutrient emissions from field runoff while ensuring the yield being not significantly affected.Under the condition of returning wheat straw to the field,the application of reduced nitrogen fertilizer compared to constant nitrogen fertilizer resulted in an average reduction of 34.92％,15.47％,35.37％,and 53.93％in COD,DOC,TN,and TP emissions from surface water in silt soil rice fields,while there was 12.01％reduction in rice yield.Meanwhile,the average reduction of COD,TN,and TP emissions from surface water in clay soil rice fields was 24.82％,23.75％,and 2.84％,respectively,while rice yield increased by 3.99％.In summary,reducing the application of nitrogen fertilizer together with returning straw to the field is beneficial for reducing the potential emission risks of COD、TN、NH4+-N 和 NO3_-N in surface water of both silt soil rice fields and clay soil paddy fields.Therefore,in order to stabi-lize rice yield and prevent nutrient runoff in rice fields,the application of nitrogen fertilizer in silt soil rice fields should be reduced and with multiple times during rice cultivation,and wheat straw should be avoided from returning to the silt soil field,while in clay soil paddy field the wheat straw should be mixed with nitrogen fertilizer before returning to the fields.
paddy fieldsstrawreducing nitrogen fertilizer applicationsurface waterorganic carbonnitrogen and phosphorus
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