Impacts of long-fallow wheat stubble management on soil water, microclimate, and wheat yield in a Mediterranean climate

Abstract

Inadequate soil water for timely crop establishment in dryland agricultural production systems of the inland Pacific Northwest is a key limiting factor in crop production. It is important to identify management practices that reduce soil water evaporation in the long fallow season prior to seeding wheat (Triticum aestivum L.) in the fall. In a 2-year study, we assessed the impacts of four residue management approaches (conventional stubble height, high stubble left standing, high stubble mowed in spring, and residue removed) in conjunction with two row orientations (north-south vs. east-west) at low and intermediate precipitation dryland agriculture sites. Soil cores to a 120-cm depth were collected at the beginning and end of each fallow season. Near-surface microclimate data (relative humidity, air temperature, soil temperature, and windspeed) were collected. Taller stubble had significantly lower windspeed compared to short residue heights. Higher soil temperatures were observed where residue was removed, but higher air temperatures were observed in high stubble. Differences in snow capture were noted during one snowfall event with high winds. Row orientation demonstrated little impact on any of the parameters. No statistically significant (p < 0.05) differences were found between treatments in wheat yield, fallow soil water storage, or reference evapotranspiration. The results of this study suggest that while residue management can have effects on microclimate, it did not lead to differences in soil water storage or wheat yield in a climate where little precipitation is received for the last 3 months of the fallow season.