Spacing between rows: effects on water-use efficiency of double-cropped wheat and soybean

SUMMARYProductivity and water resource usage efficiency are crucial issues in sustainable agriculture. The aims of the present research were to compare and evaluate the soil moisture content (SMC), evapotranspiration (ETa), yield, water-use efficiency (WUE), and net return of winter wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.] under different plant population distribution patterns and to identify the possible ways to improve water utilization. Using the same plant population for a given crop, the experiments consisted of four spacings between rows (row spacings) for winter wheat (cvar Shannong 919) under both rainfed and irrigated conditions and five row spacings for summer soybean (cvar Ludou 4) under rainfed conditions. For winter wheat, the stem number with row spacing of 49 cm was the lowest in all treatments. The SMC was enhanced by irrigation, particularly at the 10–40 cm depth. The yield and WUE were negatively correlated with row spacing and were greater with narrower row spacing than with wider rows. For soybean, SMC in uniform distribution (spacing between plants) treatments was greater at lower depths than at shallower depths for each row spacing treatment. A high yield, WUE and net return of winter wheat and soybean can be achieved with narrower row spacing. Combining winter wheat row spacing of 14 cm with soybean row spacing of 18 cm and soybean row spacing of 27 cm is a highly suitable planting system for the plains of Northern China.