Response of DEKALB® Brand Corn Products to Irrigation and Seeding Rate

​Trial Objective

  • With the increase in limited irrigation due to reductions in pumping capacity or restrictions on the amount of water producers can pump over a certain time frame, it is imperative that Bayer Crop Science tests products under varying irrigation rates to supply better corn product recommendations by irrigation level.
  • The objective of this study was to determine the yield response of key DEKALB® brand corn products for the region based on seeding rate and irrigation amount.

Research Site Details

  • Seven DEKALB® brand corn products were planted at 24,000, 30,000, 36,000, and 42,000 seeds/acre under full irrigation (100% irrigation) and a half irrigation rate (50% irrigation). Corn products and seeding rates were replicated two times under the 50% and 100% irrigation rates.
  • The trial was irrigated with a center pivot system with drop nozzles placed just above the crop canopy.
  • May through mid-June were dry with below normal rainfall. Another dry period followed during the first three weeks of July. Late-season rainfall (mid-August through September) was above normal.
  • Weed control was excellent.
  • 200 lb of actual nitrogen was side-dressed at the V2 stage.
  • The amount of irrigation applied per pass was 0.8 and 0.4 inches at the 100 and 50% treatments, respectively, totaling 7.7 inches in the 100% treatment and 3.85 inches in the 50% treatment.
  • Some stalk lodging was observed prior to harvest.

Understanding the Results

  • Averaged across all products and seeding rates, yields were 20 bu/acre higher for the 100% irrigation than the 50% irrigation treatment. These results are very similar to what occurred in this same trial in 2017.
  • The yield response to increasing irrigation was as high as 33 bu/acre (DKC56-45RIB and DKC60-67RIB brand blends) averaged across all seeding rates. DKC57-97RIB brand blend had the lowest response to irrigation (4 bu/ acre).
  • Increasing the seeding rate from 24,000 to 30,000 seeds/acre provided the largest yield increase for most products. The average yield response across all products was 16 bu/acre with 50% irrigation, and 23 bu/acre at full irrigation.
  • The yield response to increasing the seeding rate from 30,000 to 36,000 seeds/acre was much less, with several products having lower yields, and an average of a 6 bu/acre increase with full irrigation.
  • Increasing the seeding rate from 36,000 to 42,000 seeds/acre had mixed results. Within each irrigation regime, the trend was generally for slightly lower yields.

What Does This Mean for Your Farm?

  • Producers should take care in their corn product selection and seeding rate to maximize their return based on the irrigation environment in each field.
  • While yield will typically increase with increased irrigation applied, producers should weigh the costs of applying that extra water against the increase in crop production, especially under yield-limiting conditions.
  • These data would suggest that even at reduced irrigation levels, the seeding rate should be at least 30,000 seeds/ acre as there is a consistent yield and profit penalty due to under-planting, regardless of product selection.
  • Bayer Crop Science intends to repeat these trials to evaluate product response to irrigation level and seeding rate under changing environmental conditions for the 2019 season. Readers should keep in mind that these results are from one location only, and should look at results from multiple sites before drawing conclusions.
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