Reducing Environmental Risk by Improving N Management in Intensive Chinese Agricultural Systems

Key Laboratory of Plant and Soil Interactions, Ministry of Education, China, and College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 03/2009; 106(9):3041-6. DOI: 10.1073/pnas.0813417106
Source: PubMed


Excessive N fertilization in intensive agricultural areas of China has resulted in serious environmental problems because of atmospheric, soil, and water enrichment with reactive N of agricultural origin. This study examines grain yields and N loss pathways using a synthetic approach in 2 of the most intensive double-cropping systems in China: waterlogged rice/upland wheat in the Taihu region of east China versus irrigated wheat/rainfed maize on the North China Plain. When compared with knowledge-based optimum N fertilization with 30-60% N savings, we found that current agricultural N practices with 550-600 kg of N per hectare fertilizer annually do not significantly increase crop yields but do lead to about 2 times larger N losses to the environment. The higher N loss rates and lower N retention rates indicate little utilization of residual N by the succeeding crop in rice/wheat systems in comparison with wheat/maize systems. Periodic waterlogging of upland systems caused large N losses by denitrification in the Taihu region. Calcareous soils and concentrated summer rainfall resulted in ammonia volatilization (19% for wheat and 24% for maize) and nitrate leaching being the main N loss pathways in wheat/maize systems. More than 2-fold increases in atmospheric deposition and irrigation water N reflect heavy air and water pollution and these have become important N sources to agricultural ecosystems. A better N balance can be achieved without sacrificing crop yields but significantly reducing environmental risk by adopting optimum N fertilization techniques, controlling the primary N loss pathways, and improving the performance of the agricultural Extension Service.

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Available from: Peter Christie, Jun 18, 2015
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    • "Thus, farmers prefer to use inorganic fertilizers rather than organic fertilizers to preserve crop yield, particularly in intensive agricultural systems under fluctuating environmental conditions (Smith et al., 2007). However, the long-term oversupply of inorganic fertilizers, especially nitrogen fertilizer, has resulted in nitrate pollution of groundwater, eutrophication of surface waters, acid rain and soil acidification, greenhouse gas emissions, and other forms of air pollution (Ju et al., 2009). In particular, Guo et al. (2010) reported that soil acidification had become a major problem in intensive Chinese agricultural systems. "
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    • "Agriculture practices are constantly contributing to this kind of contamination. Excessive fertilization in intensive agricultural areas has caused some serious environmental problems because of water and soil enrichment with NO 3 − of agricultural origin (Ju et al., 2009). Recently nitrate pollution has also been correlated with urban areas. "
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