Dryland Corn Seeding Rate and Row Configuration Impacts on Biomass, Grain Yield, and Water Use.

The lack of plant-available water reduces crop yield potential in the Northern Great Plains. Practices shown to improve soil water relationships in dryland corn include altering seeding rate and row configuration, though these have not been reported in regions that receive limited annual precipitation like the average 325 mm of the NGP. A study was initiated in 2007 to determine seeding rate and row configuration impacts on dryland corn yield and water use. Two sites in north eastern Montana were planted at four rates (2.47, 3.71, 4.94, or 6.18 plants m^-2) in a factorial design (five reps) in conventional 0.61 m rows or in a skip-row configuration with every third row not planted. Soil water in skip-row plots was monitored during the growing season with a neutron probe. Above-ground biomass yield showed a slight inverse relationship with planting rate, and was on average 8.5% greater in conventional than skip-row corn. Grain yield showed a strong inverse relationship with planting rate and ranged from 1.0 to 3.5 Mg ha^-1 for the highest and lowest seeding rates, respectively, indicating a greater proportion of total biomass was made up of grain as planting rates decreased. Grain yield averaged 7.5% greater in conventional than skip-row corn for the two lower planting rates, though for the two higher planting rates yield was 15.4% greater for skip-row than conventional corn. Soil moisture monitored at the 0.91 m depth in the skipped row indicated little difference between the highest and lowest seeding rates. Conversely, moisture at the 0.46 m depth suggested the highest seeding rate depleted available soil moisture earlier in the season, limiting grain fill potential. The first year’s data suggests that for areas with low rainfall, improvements in corn grain yield can be made by adjusting seeding rates to 2.47 plants m^-2 or lower.