Defining a dryland grain sorghum production function for the Central Great Plains

Authors: Nielsen, David; Vigil, Merle

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/2017
Publication Date: 7/12/2017
Publication URL: https://handle.nal.usda.gov/10113/5763057
Citation: Nielsen, D.C., Vigil, M.F. 2017. Defining a dryland grain sorghum production function for the Central Great Plains. Agronomy Journal. 109:1582-1590.

Interpretive Summary: Grain sorghum is a potentially productive dryland crop for diversifying Central Great Plains cropping systems. A water use-yield production function was defined from 11 years of water use and yield data collected at Akron, CO that demonstrated a strong linear relationship between water use and yield. Yield increased by 33.1 kg/ha per mm of water use (13.4 bu/a per inch of water use). The production function was used to estimate yields using a long-term precipitation record that predicted the probability of producing at least a grain yield of 4000 kg/ha (64 bu/a) would be 18% if available soil water at planting was 111 mm (4.4") and 92% if available soil water at planting was 259 mm (10.2"). The water use-yield production function and the probability graphs generated by this project will help farmers determine the risk involved in incorporating grain sorghum production into their cropping systems.

Technical Abstract: Grain sorghum (Sorghum bicolor L. Moench) is a drought tolerant C4 species capable of making use of limited available water supplies and is suitable for dryland crop rotations in the central Great Plains. In order for farmers to assess the production risk encountered when utilizing sorghum in rotations, a water use-yield production function would be useful. Previously published production functions vary widely in reported slope of the relationship between water use and grain yield, with many of those slopes being much less than expected for a C4 species. The objectives of this experiment were to determine a water use-yield production function applicable to grain sorghum grown in the central Great Plains and to use that production function with a long-term precipitation record to assess production risk. Sorghum water use and yield data were collected from 2006 to 2016 at Akron, CO and a production function was determined by linear regression (Yield [kg ha-1] = 33.1 X (water use [mm] – 259). A grain yield of at least 4000 kg ha-1 would be expected to occur 18% of the time if plant available soil water at planting was 111 mm and 92% of the time if 259 mm was available. Both the production function and the probability exceedance graphs will be useful to farmers in assessing production risk as they consider incorporating grain sorghum into dryland crop rotations in the central Great Plains.