Best crop management practices increase rice yield and
   nitrogen use efficiency

【Objectives】Rice is one of the main staple crops in China. In order to meet the increasing demand of rice production for growing population with even reduced rice cultivation area, rice farming systems must be managed to achieve the goal of high rice productivity and primary resources (e.g. nitrogen and water) use efficiency while without further degradating environmental integrity. 【Methods】 Based on 403 on-farm trailsconducted in China’s major rice producing provinces (Including Hunan, Hubei, Guangdong, Anhui, Jiangsu and the Great Chongqing Area) from 2008 to 2011, nitrogen application rate, rice yield, nitrogen use efficiency (partial factor productivity, agronomic efficiency and recovery efficiency), nitrogen uptake and dry matter accumulation dynamics of rice plant during the main period of rice growth (tillering stage, panicle initiation stage, full heading stage and mature stage) were compared between treatments of conventional farmers’ practices (FPs) and the best crop management practices (BCMPs). The main technology of best crop management practices was optimum nitrogen management with side dressing while control the total amount of application, customized application rate of phosphorus and potassium by monitoring available phosphorus and potassium in the soil, increased transplanting density and optimized water management through controled dry and irrigation cycles after midseason drainage. 【Results】 Compared with FPs, the yield of BCMPs was 7917.0 kg/hm2 and increased significantly by 690.6 kg/hm2(9.6%) (P0.05) while nitrogen fertilizer application was significantly reduced by N 41.4 kg/hm2(20.3%) (P0.05). The nitrogen partial factor productivity, agronomic efficiency and recovery efficiency of BCMPs were significantly higher than those of FPs by 36.2%, 75.3% and 13.6 percentage points,respectively (P0.05). Nitrogen uptake and dry matter accumulation of rice plant under FPs were greater than those of BCMPs during earlier stage. After full heading stage, nitrogen uptake and dry matter accumulation of rice plant under treatment of BCMPs were greater than those of FPs. During mature stage, the nitrogen uptake of rice plant under treatment of FPs and BCMPs were 151.7 kg/hm2 and 165.9 kg/hm2, and dry matter accumulation were 12914.2 kg/hm2 and 13796.1 kg/hm2, respectively (P0.05). The dry matter accumulation after flowering was significantly different between FPs and BCMPs, which was 4045.2 kg/hm2 and 4654.5 kg/hm2, respectively (P0.05). Panicles number per square meter, spikelet number per panicle and 1000-grain weight of BCMPs were 243.2, 154.2 and 26.9 g respectively, which were significantly greater than those of FPs (P0.05). 【Conclusions】 Improved crop management practices as BCMPs could increase yield by 9.6% while reduce nitrogen and water use. These best crop management techniques are convenient and easily adopted practices that may be applied widely in rice cropping systems. This study provides the guide for sustainable rice-based cropping systems.