Consideration of dryland corn seeding rate after drought

Nebraska, like many parts of the western Corn Belt, is experiencing one of the most severe droughts in decades. Soil moisture storage throughout the rooting depth was largely depleted by the end of the growing season, particularly in dryland fields. Soil water recharge during the coming winter and spring will be critical to setting plant population for next year’s corn in dryland systems. This is because yield response to plant population in dryland fields could be muted if soil water storage is low at the start of the growing season and rainfall during the growing season cannot meet crop water demand.

Using the Hybrid-Maize model, we simulated dryland corn yield responses to different plant populations at two locations: North Platte (representing west central Nebraska) and Mead (representing southeast Nebraska). Each simulation scenario was a combination of two factors:

• plant population of 20,000, 25,000 or 30,000 per acre, and
• soil moisture, of silt loam soil, at planting of 100% (about 3.1 inches water/foot), 75% (about 2.6 inches water/foot), or 50% (about 2.2 inches water/foot) of field capacity (F.C.) throughout a 5-foot rooting depth.

For both locations, simulations were run over 31 years (1982 to 2012) of weather data, using May 1 as the sowing date. A hybrid maturity of 2500 GDD (CRM of about 103 days) was used for North Platte while a maturity of 2700 GDD (CRM of about 113 days) was used for Mead. Simulation results presented below are means of 31 years of simulations at each site.

click image to zoomFigure 1. Hybrid-Maize model simulations of dryland corn yield response to three plant populations (20, 25 and 30 thousand per acre) at North Platte (upper) and Mead (lower), Nebraska in a silt loam soil with three soil moisture contents at planting (100%, 75% and 50% of field capacity, or equivalent to absolute water content of 3.1, 2.6 and 2.2 inches per foot). Each data point represents a mean of 31 years using actual weather data from 1982-2012. In North Platte (Figure 1, upper graph), dryland corn yield does not respond to increasing population from 20k to 30k per acre if soil moisture in the 5-foot rooting zone is poor (i.e., 50% F.C., or 2.2 inches/foot) at time of planting and the growing season has average rainfall (i.e., 10.4 inches). This is because low water availability throughout the growing season limits yield response to greater plant numbers. If soil water is 75% F.C. (i.e., 2.6 inches/foot) or higher by the time of planting, there is a moderate response in dryland yields to increased plant population for a season with average rainfall.