Soil Water and Soil Temperature Influences on Dryland Winter Wheat1

Abstract Effects of wheat straw mulch on soil water and soil temperature in the 0‐ to 7.6‐cm soil layer and their subsequent influence of plant development and grain yields of winter wheat (Triticum aestivum L., ‘Winalta’) were evaluated over a 3‐year period. Mulch rates of 0, 1,680, and 3,360 kg/ha were applied randomly or in bands centered over or between wheat rows planted in 35‐, 70‐, and 90‐cm row spacings. Band applications of straw were applied at the same rates per unit area as that covered by randomly applied straw but in band widths of 18, 35, and 45 cm for the respective row spacings. In a time sequence of correlations, number of tillers and number of adventitious roots were positively correlated with a moist soil‐degree day index (P=.01) based on May soil water and soil temperature measurements, number of adventitious roots was positively correlated with number of heads/ha (P=.01), and number of heads/ha was positively correlated with grain yield (P=.01). Numbers of adventitious roots, tillers, and heads and final grain yields were dependent upon the soil water and soil temperature of the 0‐ to 7.6‐cm soil layer during May. The intermediate straw mulch rate (1,680 kg/ha) applied randomly or in bands over the wheat row significantly increased the number of moist soil‐degree days and grain yields in 2 of 3 years compared to bare fallow or the high straw mulch rate (3,360 kg/ha).