LIU Xiao-bing;S J Herbert;JIN Jian;M Hashemi;WANG Guang-hua

;Northeast Institute of Geography and Agro—ecology, CAS, Harbin Heilongjiang 150040, PRC

row spacings;light interception;water and nutrient uptake;weed control;soybean

Growing soybeans in different row-spacings introduces competition. Competition begins when the immediate supply of a single necessary factor falls below the combined demands of all plants. This paper reviews the main competition factors of genotypes,light, water, nutrients and weed in responses to row spacings for the past four decades. It demonstrated that responses of soybean genotypes to row width differ among cultivars, which depend on seasonal rainfall and irrigation. Determinate types producemore yield in narrow-rows, and cultivars with lodging resistance should be adopted in narrow-spacings, but indeterminate soybean should also be used to optimize yields in certain system. Narrow-compared with wide-row soybean (Glycine max) cultivation increases light interception (LI) and dominant components for the increase come from LAI, light extinction coefficients and branch types. Water use efficiency (WUE) and evapotranspiration are not influenced by row spacing, but seed yield could be increasedif irrigation is applied. Nutrient uptake is significantly affected by row spacing, seed yields and uptake of N, P, K in plants increases with decreasing row spacing, and the effects depend on the fertilizer levels. Other factors rather than row spacingaf-feet nitrogen fixation. Weed density, peak time and periodicity of weed emergence are not affected by row spacing, but better complementary weed control by the herbicides at the used doses can be obtained in narrow spacing due to the reduced weed number and dry weight. More researches are required to investigate the physiological responses, nutrient and water uptake and translocation, light utilization at different layers of canopy and soil environment changes in different row-spacings.