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• Three crop rotations were studied in Chongqing over five years. • Reduced fertilizer promoted grain yields and environmental and economic benefit. • The rice-wheat rotation produced the highest grain yield and economic benefit. • The maize-wheat rotation was not suitable for Chongqing. • The rice-flooded fallow rotation is the most suitable system for Chongqing. A suitable crop rotation with optimum fertilizer application can balance the need for high crop yields with minimal environmental risk. This has not yet been achieved in China, and the Chinese Government now requires rotations that include a fallow period with the aim of improving soil quality. As a step towards achieving these aims, a 5-year field experiment was carried out to evaluate the effects of different rates of nitrogen (N) fertilizer in three typical and acceptable crop rotations on grain yield, nitrogen use efficiency (NUE), N balance and economic benefit at Jiangjin, Chongqing, China. The rotations were rice-flooded fallow (RF), rice-wheat (RW) and maize-wheat (MW). Three fertilizer treatments were tested over five years. The RW rotation with reduced fertilizer application had the highest grain yield and generated the highest economic benefit. The MW rotation was not suitable for the region that we studied because high precipitation can cause serious disease problems for the wheat. The RF rotation with reduced fertilizer application proved to be the best system for ensuring food security, increasing economic benefit and reducing environmental risk. [ABSTRACT FROM AUTHOR]

Reactive nitrogen (Nr) plays a key role in the atmospheric environment and its deposition has induced large negative impacts on ecosystem health and services. Five-year continuous in-situ monitoring of N deposition, including wet (total nitrogen ( W TN), total dissolved nitrogen ( W TDN), dissolved organic nitrogen ( W DON), ammonium nitrogen ( W AN) and nitrate nitrogen ( W NN)) and dry ( D NH 3 , D HNO 3 , D pNH 4 + , D pNO 3 − and D NO 2 ) deposition, had been conducted since August 2008 to December 2013 (wet) and May 2011 to December 2013 (dry) in Yan-ting, China, a typical agricultural area in the central Sichuan Basin. Mean annual total N deposition from 2011 to 2013 was 30.8 kg N ha −1 yr −1 , and speculated that of 2009 and 2010 was averaged 28.2 kg N ha −1 yr −1 , respectively. Wet and dry N deposition accounted for 76.3% and 23.7% of annual N deposition, respectively. Reduced N ( W AN, D NH 3 and D pNH 4 + ) was 1.7 times of oxidized N ( W NN, D HNO 3 , D NO 2 and D pNO 3 − ) which accounted for 50.9% and 30.3% of TN, respectively. Maximum loadings of all N forms of wet deposition, gaseous NH 3 , HNO 3 and particulate NH 4 + in dry deposition occurred in summer and minimum loadings in winter. Whether monthly, seasonal or annual averaged, dissolved N accounted for more than 70% of the total. N deposition in the central Sichuan Basin increased during the sampling period, especially that of ammonium compounds, and has become a serious threat to local aquatic ecosystems, the surrounding forest and other natural or semi-natural ecosystems in the upper reaches of the Yangtze River. [ABSTRACT FROM AUTHOR]