Impact of Seeding Rate and Stand Reduction on Irrigated XtendFlex® Soybeans

TRIAL OBJECTIVE

  • Seeding rate and the overall stand health can significantly affect soybean yield potential.
  • Several biotic and abiotic factors can result in soybean stand reduction, including herbicide drift, plant pathogens and disease, drought, soil compaction and crusting, and weed pressure. Altering the initial seeding rate and potentially replanting after stand reduction to hit target yields is a crucial decision for producers.
  • This study’s objective was to determine the effect of two seeding rates and five levels of stand reduction on soybean yield potential.

 

EXPERIMENT/TRIAL DESIGN

RESEARCH SITE DETAILS

  • The trial was arranged as a randomized complete block design with four replications and two treatment factors - seeding rate and percent stand reduction.
    • Seeding Rates: 80,000 and 160,000 seeds/acre
    • Stand Reduction: 0, 20, 40, 60, and 80% were achieved by mixing a non-herbicide tolerant soybean product with the test product so that when the soybean plants were sprayed the desired percentage of stand was removed.
  • The soybean product used was a 2.7 maturity group (MG), XtendFlex® soybean product.
  • The trial was fully irrigated throughout the growing season for a total of 10.0 inches of water.
  • The trial was strip-tilled on 04/14/2022 with a base fertilizer application of 29 lbs of nitrogen/acre, 60 lbs of phosphorus/acre, 25 lbs of sulfur/acre), and 0.25 lbs of Zinc/acre.
  • Weed Control:
    • Pre-Emerge applied on 5/30/2022
      • 32 fl oz/acre Roundup PowerMAX® herbicide
      • 4 fl oz/acre Zidua® SC Herbicide
      • 5 fl oz/acre Willowood Sulfentrazone 4SC herbicide
      • 8 fl oz/acre Dimetric® Liquid herbicide
    • Post –Emerge applied on 6/12/2022
      • 32 fl oz/acre Roundup PowerMAX® herbicide
      • 10 fl oz/acre Section® Three Herbicide
      • 48 fl oz/acre Warrant® Herbicide
      • 22 fl oz/acre XtendiMax® with VaporGrip® Technology (Restricted Use Pesticide)*
      •  8 fl oz/acre SentrisTM  (Volatility Reducing Agent)
      • 0.5% V/V OnTarget® (Drift Reduction Adjuvant)
    • Late Post applied on 7/5/2022
      • 16 fl oz/acre Clethodim 2E herbicide
    • Late Post applied on 7/12/2022
      • 32 fl oz/acre Liberty® herbicide
  • Soybean harvest population counts were taken prior to harvest.
  • Total weight, test weight, and moisture content were collected with a plot combine to calculate yield per acre.

 

*XtendiMax® herbicide with VaporGrip® Technology is part of the Roundup Ready® Xtend Crop System, is a restricted use pesticide and must be used with VaporGrip® Xtra Agent (or an equivalent volatility reduction adjuvant). For approved tank-mix products (including VRAs and DRAs), nozzles and other important label information visit XtendiMaxApplicationRequirements.com. Applicators must check XtendiMaxApplicationRequirements.com no more than 7 days before application of this product for additional labeling, including state restrictions. Where applicable, users must comply with additional requirements found on the website.

UNDERSTANDING THE RESULTS

  • There was a significant interaction between the seeding rate and stand reduction percentage for both final soybean harvest population and yield (Figures 1 and 2).
  • The final soybean harvest populations reflected a consistent reduction with the stand reduction treatments applied (Figure 1).
  • Note that final stands were very low with only about 15,000 plants/acre remaining when the 80,000 seeding rate was reduced by 80% (Figure 1).
  • The higher seeding rate of 160,000 seeds/acre resulted in an average soybean yield of 66.1 bu/acre, compared to 63.4 bu/acre at a seeding rate of 80,000 seeds/acre (Figure 2).
  • There were significant differences in average soybean yield (bu/acre) due to stand reduction within the 80,000 seeds/acre seeding rate. The 20% stand reduction had the highest average yield of 74.4 bu/acre, followed by the 0% stand reduction at 68.5 bu/acre. The 80% stand reduction resulted in average soybean yields that were significantly lower than the other stand reduction levels, averaging just over 42 bu/acre (Figure 2).
  • Greater stand reduction resulted in visually higher weed pressure in the plots. This was possibly due to slower canopy closure allowing increased light penetration to the soil surface for weed seed germination. (Figure 3).

 

KEY LEARNINGS

  • Depending on the seeding rate (seeds/acre), stand reduction due to growing conditions or management practices may result in no difference in soybean yield potential.
  • The relative plasticity of a soybean plant’s growth and seed production can compensate for stand reduction.
  • Reduced soybean stands can potentially increase the potential for weed seed germination and weed competition.
  • Farmers should work with their local seeds sales team member to help identify the best XtendFlex® soybean product for their fields.

 

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