Mechanism Of Controlled Release And Common Urea Combined Application To Increase Yield And Reduce Emission Of Maize

Single-use base fertilizer application of controlled release urea（CRU）and common urea（U）was a simple method to optimize nitrogen supply in maize production season.In order to explore the influence mechanism of controlled release urea combined with common urea on maize growth,grouting process and N₂O emission reduction,field experiments were conducted on two typical soil types（sandy soil and clay soil）in Northeast China for four consecutive years from 2018 to 2021.This paper mainly studied the root growth and development of maize at the spinneret stage,leaf senescence after spinneret,filling characteristics and their relationship with yield under the combined application of controlled release and common urea,analyzed the profile N₂O distribution and emission characteristics during the growth stage of maize,and further studied the relationship between surface and profile N₂O emission.The environmental effects,costs and comprehensive benefits during the life cycle of maize were evaluated,which provided a new insight into the mechanism of increasing yield,reducing emission and increasing efficiency of maize by MCU method,and had practical significance for optimizing nitrogen management in maize production.The main research results are as follows:1.Compared with MCU0%（common urea 100%）,MCU30%（controlled release urea 30%,common urea 70%）promoted maize root growth by distributing more nutrients and formed more crown roots and lateral roots to increase root length.Under the condition of sufficient late nitrogen supply,the root character of MCU30%was well developed,which could increase nitrogen uptake after spinning,delay leaf senescence,and improve grain filling and grain weight after spinning.On average,the yield of MCU30%on sandy soil and clay soil is 11.8 t ha^-1and13.3 t ha^-1,which are 22.3%and 11.7%higher than that of MCU0%,respectively.Compared with MCU0%,the final total green area（GLA）of MCU30%in sand soil is 49%higher.2.Compared with MCU0%,MCU30%,fast nitrogen fertilizer and slow nitrogen fertilizer are applied in a reasonable combination,which is suitable for crop nutrient absorption.The early fast fertilizer is suitable to reduce the early N₂O emission and section N₂O residue.The mean N₂O emission flux MCU30%of sandy soil and clay soil decreased by 18.9%and 19.4%,respectively,compared with MCU0%,and the cumulative N₂O emission of MCU30%decreased by 18.8%and 19.1%,respectively,compared with MCU0%.The results of profile N₂O showed that the concentration of N₂O in the near surface and deep soil changed little,and the emission of N₂O mainly occurred in the topsoil during the growth period.The input of nitrogen fertilizer increased the contribution of N₂O in the surface soil,indicating that nitrogen fertilizer was the main factor affecting the emission intensity of N₂O.3.Compared with MCU0%,MCU30%increased the cost of fertilizer,but the environmental cost in the process of fertilizer production,transportation and use was reduced,and the yield was increased,thus increasing the economic and social benefits.On both soil types,the value increment and social benefit of MCU30%were the highest.On sandy soil,the value increment of MCU30%(18,400 yuan ha^-1)was increased by 27.8%compared with that of MCU0%(14,400 yuan ha^-1).On clay soil,MCU30%(14,400 yuan ha^-1)increased by 25.2%compared with MCU0%(11,500 yuan ha^-1).In conclusion,MCU30%combines the fast available nitrogen with slow available nitrogen fertilizer,and the ratio is suitable for the growth and development of maize during the growth period,promotes the growth of root system,improves the nutrient absorption after spinning,further improves the source-sink relationship during the filling period,and finally increases the number of grains per ear and grain yield,while reducing the emission of N₂O.Increased economic and social benefits.The results of the study explain the mechanism of 30%controlled release urea and 70%common urea mixed to promote maize increase yield and reduction emission,and provide an important basis for productivity and optimal nitrogen management under the state of one-time light and simplified fertilization in Northeast China.