Improving Dryland Organic Winter Wheat Performance with the Inclusion of Composted Cattle Manure and Cover Crops
[Thesis]
Helseth, Christina
Norton, Urszula
University of Wyoming
2020
103
M.S.
University of Wyoming
2020
Winter wheat (Triticum aestivum, L.) production in semi-arid environments is challenged by nutrient- deficient soils and droughts. A high rate (50 Mg ha−1) of composted cattle manure (compost) applied as a single event was shown to retain soil health benefits in a similar climate in Utah after sixteen years but has not been evaluated in the Northern High Plains. To expand potential benefits, planting spring cover crops during the fallow has been recommended. This study quantified the effects of a single compost application (0, 15, 30, and 45 Mg ha−1) combined with annual cover crop planting on soil and crop performance after four to five years. Soil, plant, and greenhouse gas monitoring was conducted seasonally. Results showed no synergy between compost and cover crops but these two practices affected soils and crop yield in different ways. The 45 Mg ha−1 of compost elevated soil organic carbon (SOC), total nitrogen (N), and available phosphorus. Elevated soil labile N in the fallow and no increases in nitrous oxide emissions point to efficient soil labile N conservation. Cover crops were not beneficial: they reduced soil water content, reduced wheat grain protein, and did not suppress weeds. They did, however, add SOC and labile N to the soil and increased methane assimilation. The results of this study suggest that the application of a high rate of compost should be a stand-alone treatment. More research is needed for the integration and management of cover crops.