Wheat residue mulch and anti-transpirants improve productivity and quality of rainfed soybean in semi-arid north-Indian plains

Soybean (Glycine max L. Merr.) is largely grown in moisture-stressed conditions resulting in low yield. A 3-year field experiment was conducted during rainy seasons of 2012-2014 to determine: (i) the effects of straw mulches and anti-transpirants on soil moisture retention, rainwater-use efficiency (RWUE), photosynthesis, growth, yield, and quality of soybean (cv. PS 1347), and (ii) the influence of climate (year) on responses of soybean to straw-mulch and anti-transpirant application. The treatments included two mulching treatments, no-mulch and wheat residue mulch (at 5 Mg ha−1), and the use of anti-transpirants, MgCO3 (5%), glycerol (5%), Na2CO3 (2%), KNO3 (1%) and no-anti-transpirant (control) sprayed 15 days after flower initiation. Wheat straw mulching enhanced surface soil (0-30 cm) moisture content by 20% over plots under no-mulch, improved leaf SPAD (soil plant analysis development) values, net-photosynthetic rates and boosted soybean grain yield by ∼16% over no-mulching. Plots with wheat straw mulching also had ∼18, 18 and 17% higher protein yield, oil yield and RWUE compared with no-mulch plots. Spraying MgCO3 and KNO3 along with wheat residue mulching (5 Mg ha−1) caused significant enhancement in grain-and protein-yield, and RWUE over control. However, Na2CO3 was not a suitable anti-transpirant as it reduced soybean growth, yield and quality. These results suggest that wheat residue mulch and anti-transpirants, MgCO3 and KNO3, can significantly improve the yield and quality of soybean in moisture-stressed rainfed environments.