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SOIL & WATER MANAGEMENT & CONSERVATION

In-Season Optical Sensing Improves Nitrogen-Use Efficiency for Winter Wheat

^a College of Resources & Environ. Sciences, China Agricultural Univerisity, 100094, Beijing, China
^b College of Ecology & Environmental Science, Inner Mongolia Agricultural University, 010019, Hohhot, Inner Mongolia, China
^c Dep. of Plant and Soil Sciences, Oklahoma State Univerisity, Stillwater, OK, 74078
^d Institute of Agriculture, Resource, and Environment, Hebei Academy of Agriculture and Forestry Sciences, 050051, Shijiazhuang, Hebei Province, China

^* Corresponding author (chenxp{at}cau.edu.cn).

Optical sensor-based N management strategies are promising approaches to improve N-use efficiency (NUE) and reduce environmental pollution risk. The objective of this study was to evaluate an active optical sensor-based in-season N management strategy for winter wheat (Triticum aestivum L.) in the North China Plain (NCP). Initially, 10 field experiments were conducted at four villages in NCP in the 2004/05, 2005/06, and 2006/07 growing seasons to evaluate the in-season N requirement prediction developed by Oklahoma State University. Then the N application rates, winter wheat grain yield, NUE, economic returns, residual N content after harvest and apparent N loss were compared among three different management systems on a total of 16 farmer fields in 2005/2006 and 14 farmer fields in 2006/2007. The systems included a sensor-based system, a soil test-based approach crediting soil residual mineral N (N_min) to different depth at different growth stages, and common farmer practices. Averaged across site-years, the sensor-based, soil N_min–based N management strategies, and farmer practices produced similar grain yields but used 67, 88, and 372 kg N ha^–1, respectively. Nitrogen-use efficiencies were 61.3, 51.0, and 13.1% for the three methods of N recommendations, correspondingly. Their residual N content in the soil and apparent N loss were 115, 122, and 208 kg N ha^–1, and 4, 15, and 205 kg N ha^–1, respectively. The optical sensor-based N management strategy is relatively easy to use, has better potential to improve NUE and economic returns, and reduces residual soil N content and apparent N loss than other methods currently used in the NCP.

Abbreviations: CK, check • Con, conventional N fertilization • GDD, growth degree days • INSEY, in-season estimated yield • NCP, North China Plain • NDVI, normalized difference vegetation index • N_min, soil residual mineral N • NUE, nitrogen use efficiency • Opt, optimized N fertilization • PNG_YPN, predicted non-N limiting grain N uptake • PNG_YP0, predicted grain N uptake without additional N • RI, response index • YPN, non-N limiting yield potential • YPO, yield potential without additional N