Nutrient and irrigation impacts on winter wheat yield and quality

Winter wheat yield in the western United States is limited by two major factors: nutrients (such as nitrogen) and moisture. This research examined the interactions of moisture and nutrient supply on yield, flour quality, agronomic traits, and both organic and inorganic nutrient fate within the soil profile with both hard white (Golden Spike) and soft white (ID 576) winter wheat under line-source irrigation. The line-source irrigation system provides evapotranspiration replacement in the nearest strip while the furthest strips were rain fed only. Nitrogen sources were applied in ten nutrient treatments ranging from 0-224 kg N ha-1 (supplied as inorganic ammonium nitrate) and 0-100 Mg ha-1 dry weight compost (organic material supplied as composted dairy waste). Compost decreased bulk density and increased gravimetric water content at the incorporated depth. The improved gravimetric water content suggests compost-amended soils can hold more moisture over a greater period of time. Compost treatments increased plant tillers and early plant height and dry matter production. When moisture was present, similar yields were obtained from compost and inorganic nitrogen fertilizers, although when moisture was limited, compost increased yield above that achieved by inorganic nitrogen fertilizers. Compost will have a greater impact on final yields in rain-fed climates rather than irrigated when compared to inorganic fertilizers.