LAUSR

Abstract In North-west china, the soybean (Glycine max L. Merr.) is grown in June, when the climate is dry, and soil has limited moisture contents. Moisture deficiency limits the soybean biomass. We studied the effects of wheat straw mulching and nitrogen on soybean growth, physiology and soil properties in three-year field experiments. The treatments included three straw mulching i.e. S1 (0 kg ha−1), S2 (3000 kg ha−1) and S3 (6000 kg ha−1), and three nitrogen rates i.e. N1 (0 kg N ha−1), N2 (21.6 kg N ha−1), and N3 (27 kg N ha−1). Full mulching (S3) significantly increased moisture retention (7.4%) and decrease soil temperature (3.0%) in 0–20 cm soil depth, increased photosynthesis, SPAD-value, leaf area, leaf area index, growth, and soybean grain yield (20.8%) over no-mulching (S1). The S3 improved the roots mass, nodules number and weight than S1. The application of 27 kg N ha−1 or 100% N fertilizer (N3) had significantly increased photosynthesis, SPAD-value, growth, and biomass and seed yield of soybean over no-N application (N1). It was concluded that using straw mulching (6 Mg ha−1) can change the soil hydrothermal regime for provision of favorable condition for soybean growth when 27 kg N ha−1 was used in semi-arid condition of North-west China.