Nitrogen Cycling And Balance In Wheat-maize Rotation Field In Piedmont Plain Of MT Taihang In The North China Plain

The main nitrogen (N) cycling pathways, such as nitrification-denitrification, N₂O emission, ammonia (NH₃) volatilization, nitrate (NO₃-N) leaching, net soil N mineralization, N uptake by crops, were monitored in 1 ha wheat-maize rotation field. The relative significance of different N loss was evaluated. The characters of N inputs and outputs from farmland of Piedmont Plain of MT Taihang were quantified and the N balance was analyzed so as to provide some important information for establishing optimized N management for diminishing N losses and increasing N use efficiency. The results indicated that NH₃ volatilization and NO₃-N leaching loss were the important pathways of N losses and were the important causes for low N use efficiency. The annual NH₃ volatilization was 60 kg N ha^-1 and NO₃-N leaching loss was 6⁸4 kg N ha^-1, according for 15% and 1.4%²0.3% of the applied N fertilizer, respectively. The nitrification-denitrification loss was not very important pathway of N loss, but the effect on environment cannot be overlooked. The annual nitrification-dinetrification loss was 2.02¹0.49 kg N ha^-1, according for 0.51%¹.37% of applied N. NH₃ volatilization, nitrification-denitrification and NO₃-N leaching were mainly occurred after N applied and irrigation or heavy rainfall events and the loss under maize was larger than that under wheat.The N balance was surplus in wheat-maize rotation field under traditional agricultural management in the study area. The N surplus under wheat was+115.5⁺124.5 kg N ha^-1, higher than that under maize. The N balance under maize was lightly surplus or little wane as the result of heavy N losses and the value was -54.6⁺14.3 kg N ha^-1. In order to improve crop yields and N use efficiency and to keep N balance in farmland the measurements should be taken, such as improving N application methods especially N deep application to decrease NH₃ volatilization and reducing irrigation amount especially avoiding heavy irrigation at one time to diminish NO₃-N leaching.