Hydrologic separation and their contributions to N loss in an agricultural catchment in hilly red soil region  

作　　者：Yaji WANG Lei GAO Xinhua PENG 

机构地区：[1]State Key Laboratory of Soil and Sustainable Agriculture,Institute of Soil Science,Chinese Academy of Sciences,Nanjing 210008,China [2]University of Chinese Academy of Sciences,Beijing 100081,China

出　　处：《Science China Earth Sciences》2019年第11期1730-1743,共14页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant Nos. 41571130053 & 41771263);the Frontier Program of the Institute of Soil Science (Grant No. ISSASIP1648)

摘　　要：The impacts of hydrological processes on N loss is of great value to understand the N transport at catchment scale,which is far from clear. Rainfall, soil water, groundwater and stream water and their N concentrations were monitored from March 2017 to February 2018 in Sunjia agricultural catchment of the red soil critical zone. Objectives of this study were:(1) to determine the dynamics of N concentration of different waters and their N loads;(2) to assess their contributions to N load of streamflow in the paddy and upland mixed agricultural catchment. Our results showed that the N concentrations of soil water(4.8 mg L^(-1)) and groundwater(6.0 mg L^(-1)) were the highest, approximately 2 to 5 times higher than those of stream water(2.7 mg L^(-1)), rain water(1.7 mg L^(-1)) and irrigation water(1.2 mg L^(-1)). The N net loss of the catchment(38.2 kg ha^(-1) yr^(-1))accounted for 15% of the total fertilizer N input. Rainy season(April–June) was a high-risk period of N loss, contributing to more than one third of the total annual loss amount. Using end-member mixing analysis model(EMMA), we found groundwater(whose discharge accounted for 25% of the catchment streamflow) was an important source for the N loss in the agricultural catchment. Even in this catchment with coexisting upland and paddy field ecosystems, identified end-members could be used to predict the N load well(R^2>0.87, p<0.001). These results can deepen our understanding of the relationship between hydrological process and N transport in the red soil critical zone and are also helpful to improve the water and fertilizer management in subtropical agricultural catchment.The impacts of hydrological processes on N loss is of great value to understand the N transport at catchment scale,which is far from clear. Rainfall, soil water, groundwater and stream water and their N concentrations were monitored from March 2017 to February 2018 in Sunjia agricultural catchment of the red soil critical zone. Objectives of this study were:（1） to determine the dynamics of N concentration of different waters and their N loads;（2） to assess their contributions to N load of streamflow in the paddy and upland mixed agricultural catchment. Our results showed that the N concentrations of soil water(4.8 mg L-1) and groundwater(6.0 mg L-1) were the highest, approximately 2 to 5 times higher than those of stream water(2.7 mg L-1), rain water(1.7 mg L-1) and irrigation water(1.2 mg L-1). The N net loss of the catchment(38.2 kg ha-1 yr-1)accounted for 15% of the total fertilizer N input. Rainy season（April–June） was a high-risk period of N loss, contributing to more than one third of the total annual loss amount. Using end-member mixing analysis model（EMMA）, we found groundwater（whose discharge accounted for 25% of the catchment streamflow） was an important source for the N loss in the agricultural catchment. Even in this catchment with coexisting upland and paddy field ecosystems, identified end-members could be used to predict the N load well（R2>0.87, p<0.001）. These results can deepen our understanding of the relationship between hydrological process and N transport in the red soil critical zone and are also helpful to improve the water and fertilizer management in subtropical agricultural catchment.

关 键 词：End-member MIXING analysis model HYDROLOGICAL SEPARATION GROUNDWATER N load Red soil critical ZONE 

分 类 号：S15[农业科学—土壤学]