Evapotranspiration, crop coefficient and yield for drip-irrigated winter wheat with straw mulching in North China Plain

A field experiment was conducted for three consecutive years (2013.10-2016.6) to study the effects of straw mulching with three drip-irrigation schedules on crop evapotranspiration (ETc), crop coefficient (Kc), grain yield (Y) and water-use efficiency (WUE), and the three drip irrigation lower limits and upper limits were from 55% field capacity (FC) to 75% FC, 65% to 85% FC and 75% and 100% FC respectively. Mulching significantly decrease the total irrigation amount compared with non-mulched when the soil water content was remaining within 65%-85% FC. Mulching also significantly (p < 0.05) decrease the seasonal crop evapotranspiration (ETcs) and increased Y when soil water content was remaining within 75%-100% FC. Under the same sufficient drip irrigation schedule, mulching significantly increase the WUE. Mulching decreased the total cumulative soil evaporation (Es) amount to 19-34 mm, and mean daily Es was significantly reduced by 25%-41% compared with non-mulching. The Kc of well-watered treatments agreed well with the corrected Kc-FAO curve, and the corrected Kc-FAO for this study field may underestimate the real Kc of winter wheat for the mid-season. Generally, straw mulching did not significantly alter the Kc value (p > 0.05) compared with non-mulched treatments under the same drip-irrigation schedule when winter wheat entered the fast development stage. The straw mulching not only clearly decreased evaporation coefficient Ke, but also increased basal crop coefficient Kcb of winter wheat. In addition, with the same less water irrigation or seasonal crop evapotranspiration (ETcs) consumption, mulching had potential advantage of improving Y. Finally, the treatment with soil water content remaining within 65%-85% FC and combined with straw mulching, was an optimal combination of drip-irrigation schedule with agronomy for winter wheat irrigation management in the North China Plain.