Effect of Dicamba Formulations and Planting Date on Different Corn Products

• Dicamba, a growth regulator herbicide, is an effective broadleaf herbicide in corn. Producers should consider safened dicamba herbicide formulations to help protect yield potential and to help reduce plant stress from factors such as stalk brittleness or greensnap.¹

• Planting date and corn product selection are some of the major drivers for high yield potential.

• The objective of this trial was to evaluate the yield potential impact on twenty different corn products when the products were planted on two different dates and safened and unsafened dicamba formulations were applied at V5 and V9 corn growth stages.

• Trial was a split-split-plot design with planting date as the whole plot, herbicide as the sub-plot, and corn product as the sub-sub plot with five replications.
• Two corn planting dates of May 5 and May 25 were targeted to provide corn at V9 and V5 growth stages when the dicamba applications were to be applied, respectively.
• Twenty corn products were planted (Tables 1 and 2).
• Residual herbicide program applied on May 22, 2021 to the study area included:
  • Balance® flexx Herbicide (Restricted Use Pesticide) (4 oz/acre)
  • Harness® herbicide (2 pts/acre)
  • Atrazine 4L herbicide (1 qt/acre)
  • Roundup PowerMAX® (1 qt/acre) + Ammonium Sulfate (AMS) (17 lb/100 gallon)
• Three herbicide/fungicide treatments were applied on June 23 to the V5 (May 25th - planted) and V9 (May 5th - planted) growth stage plants:
  • A non-dicamba treated control:
    • Delaro® 325 SC fungicide (0.125 qt/acre) + Roundup PowerMAX® herbicide (1 qt/acre) + AMS (17 lb/100 gallon)
  • An unsafened dicamba formulation (Bold):
    • Sterling Blue® herbicide (0.5 qt/acre) + Delaro® 325 SC fungicide (0.125 qt/acre) + Roundup PowerMAX® herbicide (1 qt/acre) + AMS (17 lb/100 gallon)
  • A safened dicamba formulation (Bold):
    • DiFlexx® Herbicide (0.5 qt/acre) + Delaro® 325 SC fungicide (0.125 qt/acre) + Roundup PowerMAX® herbicide (1 qt/acre) + AMS (17 lb/100 gallon)
• Trial was sprinkler irrigated.
• Fertility program applied through strip-tillage before planting included 60 lb/acre phosphorus, 25 lb/acre sulfur, and 0.25 lb/acre zinc. Nitrogen was applied on 05/10/2021 using a stream bar at 100 lb/acre and side-dressed on 06/21/2021 with 60 lb/acre using 360 Y-DROP®.

• Early planted corn (May 5) did not have a difference in grain yield between the safened dicamba formulation and the control treatment (Figure 1).

• Corn products with the safened dicamba formulation produced an average 9.7 and 6.8 bu/acre greater yield than the unsafened dicamba formulation treatment when corn was planted on May 5 and May 25, respectively (Figure 1).

• Greater average yields were observed when corn was planted early (May 5) compared to late (May 25) (Figure 1 and Table 1).

• Although planting corn late (May 25) reduced average grain yield significantly, it is important to consider that the safened dicamba formulation had significantly higher average yields than the unsafened dicamba formulation when applied to the May 5 corn at the V9 growth stage with a similar trend observed on the corn planted on May 25 at the V5 growth stage (Figure 1).

Table 1. Average grain yield of corn products according to planting date and averaged across dicamba treatments. Bayer Water Utilization Learning Center, Gothenburg, NE. (2021)

• All corn products reached significantly higher average yields with the May 5 planting date compared to the May 25 planting date (Table 1).
• Greater average yield variability was observed with May 5 planting date with five products over 290.0 bu/acre and a low average yield of 246.8 bu/acre.
• Average yields were less variable across the corn products with the May 25 planting date (Table 1).

Table 2. Average grain yield of corn products according to dicamba herbicide formulation treatments across planting dates. Bayer Water Utilization Learning Center, Gothenburg, NE (2021)

• Eight out of 20 corn products reached significantly higher yields (more than 10 bu/acre) when treated with the safened versus the unsafened dicamba formulation (Table 2). No corn product reached significantly higher yields when treated with the unsafened compared to the safened dicamba formulation (Table 2).

• In this study, the safened dicamba formulation treatment with DiFlexx® Herbicide produced a greater average yield than the unsafened dicamba formulation.
• In addition, the safened dicamba formulation showed greater average yield in 40% of the products tested when compared to the unsafened dicamba formulation.
• Farmers should be encouraged to use DiFlexx® herbicide as an option for early weed control in corn to help lower the risk for potential crop damage and decreased yield that can be observed when using unsafened dicamba herbicide products.
• Preference should be given to planting corn early such as the May 5 planting date as it increased yield 33.9 bu/acre, on average, for all corn products tested compared to the May 25 planting date.

Reference

¹Bayer Water Utilization Learning Center Research Book. 2020. Dicamba Formulation Impact on Corn. Gothenburg, NE.