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Title: Soil and rainfall factors influencing yields of a dryland cropping system in Colorado

Author
item Sherrod, Lucretia
item Ahuja, Lajpat
item HANSEN, NEIL - Colorad0 State University
item Ascough Ii, James
item WESTFALL, DWAYNE - Colorad0 State University
item PETERSON, GARY - Colorad0 State University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2014
Publication Date: 5/1/2014
Citation: Sherrod, L.A., Ahuja, L.R., Hansen, N.C., Ascough II, J.C., Westfall, D.G., Peterson, G.A. 2014. Soil and rainfall factors influencing yields of a dryland cropping system in Colorado. Agronomy Journal. 106:1179-1191.

Interpretive Summary: The semi-arid Great Plains of the United States experience a large variation in crop yields due to variability in rainfall, soil, and other factors. We analyzed crop yields (24-year period) from a no-till rotation of wheat-corn or sorghum-fallow at three sites, each with three soil types along a catena in eastern Colorado to investigate: 1) the effect of soil properties across sites and landscape positions on crop yields; and 2) the degree in which the annual variability of crop yields was explained by soil water at planting and rainfalls during fallow, vegetative, and reproductive crop growth stages. Mean 24-years wheat and corn + sorghum yields were strongly related to soil organic C. In addition, the corn and sorghum yields were also impacted by the potential run-on of water from upslope area. We believe that the strong correlation of yields to soil carbon reflects the long-term effect of the water factors on soil productivity at different locations. However, the water factors explained less than 50% of the inter-annual variability in crop yields pooled over all soils and sites, but varying from 37 to 73% in wheat yields in individual soils at the site level and 19 to 63% in yields pooled over soils at the site level; for corn yields, the corresponding percentages were 40-45%, 16-64%, and 26-57%, respectively. Preceding fallow rainfall made the highest contribution to R2 to wheat yields whereas rainfall during reproductive period was the strongest contribution for corn or sorghum.

Technical Abstract: The semi-arid Great Plains of the United States experience a large variation in crop yields due to variability in rainfall, soil, and other factors. We analyzed crop yields (24-year period) from a no-till rotation of wheat(Triticum aestivum)-corn (Zea mays L.) or sorghum[Sorghum bicolor (L.) Moench]-fallow at three sites, each with three soil types along a catena in eastern Colorado to investigate: 1) the effect of soil properties across sites and landscape positions on crop yields; and 2) the degree in which the variability of crop yields is explained by water variables. Specifically, we explored multivariate regression relationships between: 1) mean yields and soil organic carbon (SOC), length of slope (SL), soil porosity (POR), and effective porosity (EP); and 2) annual crop yields and rainfall during the preceding fallow period, soil water at planting, and rainfall during vegetative and reproductive stages. Mean wheat and corn or sorghum yields were strongly related to the soil properties (Wheat R2=0.89; Corn/Sorghum R2=0.98). Soil organic C made the most significant contribution to R2 for all crops. This result may reflect the long-term effect of water factors on soil productivity at different locations. However, the water factors explained from only 37 to 73% of inter-annual variability in wheat yields in individual soils at the site level, 19 to 63% in yields pooled over soils at the site level, and 35 to 40% pooled over all soils and sites. For corn yields, the corresponding percentages were 16-64%, 26-57%, and 40-45%, respectively. Preceding fallow rainfall made the highest contribution to R2 to wheat yields whereas rainfall during reproductive period was the strongest contribution for corn or sorghum.