The Variable Response of Dryland Corn Yield to Soil Water Content

Authors: Nielsen, David; Vigil, Merle; Benjamin, Joseph

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/2008
Publication Date: 11/20/2008
Citation: Nielsen, D.C., Vigil, M.F., Benjamin, J.G. 2008. The Variable Response of Dryland Corn Yield to Soil Water Content. Agricultural Water Management 96:330-336.

Interpretive Summary: Growing corn in the semi-arid central Great Plains is expensive due to high costs of seed, herbicides, and fertilizers. Profitable production is risky due the highly variable nature of growing season precipitation. Farmers desire a decision support tool that will help them to determine the potential success of raising a profitable corn crop before they invest in the expensive inputs needed for production. Such a decision support tool could be developed if a reliable relationship exists between corn grain yield and available soil water at planting. This study determined that the relationship between yield and available soil water was so highly variable for corn that no reliable decision support tool could be developed. However, the study did find that the relationship between yield and available soil water varied consistently with amount of precipitation between 15 July and 25 August such that a decision support tool was developed that provides the probability of obtaining a given corn yield with a given amount of available soil water at planting. The results of that decision support tool confirm that profitable corn production under dryland conditions is a risky and speculative activity in the central Great Plains of the United States.

Technical Abstract: Farmers in the central Great Plains would like to diversify crop rotations from the monoculture of the traditional winter wheat-fallow system. Corn (Zea mays L.) could work well as a rotation crop, but inputs are expensive and farmers would like to know the chances of producing a certain yield before investing in seed, fertilizer, herbicides, etc. Information on the yield response of corn to available soil water at planting could help guide the crop choice decision regarding corn. This study was conducted to determine if a predictive relationship exists between dryland corn yield and available soil water at planting time and, if such a relationship exists, to use it to assess the risk in obtaining profitable yields. Yield and soil water data from 10 years of a dryland crop rotation study at Akron, CO were analyzed by linear regression to determine predictive relationships. The yield-soil water content production function was found to be highly variable, with slopes ranging from 0.0 to 67.3 kg ha-1 per mm of available soil water in the 0 to 1.8 m soil profile at planting. The differences in yield response to soil water were related to the amount and timing of precipitation that fell during the corn growing season. Because dryland corn yield is highly dependent on precipitation during reproductive and grain-filling stages, soil water content at corn planting cannot be used alone to reliably determine whether corn should be planted in a flexible rotational system. The predictive relationships developed in this study indicate that under typical amounts of available soil water at corn planting, profitable corn production under dryland conditions is a risky and speculative activity in the central Great Plains of the United States.