Response of Deltapine® Cotton Varieties to Plant Growth Regulator Regimes

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January 20,2021

Response of Deltapine® Cotton Varieties to Plant Growth Regulator Regimes -  2020

 

TRIAL OBJECTIVE

  • The plant growth regulator (PGR) mepiquat chloride benefits cotton production by helping to balance vegetative growth with reproductive growth. PGR applications at the appropriate rate and timing are essential for managing cotton varieties in the coastal U.S.

  • Each season new Deltapine® cotton varieties are evaluated at the Bayer Learning Center at Scott, Mississippi for a response to plant growth regulator applications in the productive Delta system.
  • The primary objectives of this study were to:
    • Evaluate the growth habit of new cotton products in comparison with existing Deltapine cotton varieties.
    • Evaluate cotton variety response to mepiquat chloride application in one of three application regimes.

 

RESEARCH SITE DETAILS

Location Scott, MS    
Soil Type  Commerce silt loam  

Previous
Crop
Corn    
Tillage
Type
Conventional 


 
Planting Date 5/12/20     
Harvest Date 10/1/20  

Potential Yield
 (lbs/acre)
1900    
Seeding Rate
(seeds/acre)
45,000

 
  • This study was set up to encourage excessive vegetative growth in a field following corn with high fertility (120 lb/acre of actual nitrogen soil applied as 32% liquid N) and irrigation applications.  

  • All other agronomic inputs (weed control, insect control, and irrigation) were per local standards for each treatment. 

  • Single replicate strip plots were planted of 6 rows x 400 feet or approximately 0.2 acre/plot. 

  • Application regimes of mepiquat chloride (standard 4.2% formulation) were as follows: (Table 1).
    • An untreated check with no PGR applied.
    • Passive regime (representing older growth management methods) – three application rates and three timings totaling 38 oz/acre applied with delayed early application on July 10, 2020, at a reduced rate.
    • Aggressive regime – three applications at maximum label rates at three timings totaling 48 oz/acre applied.

 

table Table 1. 2020 passive and aggressive PGR treatment rates and application timings.

  • Growth characteristics of new Deltapine® cotton varieties were evaluated as follows:
    • End-of-season plant height measurement indicating the growth nature of the new product.
    • Height reduction measurement from either the passively or aggressively managed treatments versus the untreated check.
    • Representative turnouts from other trials at Scott Learning Center were used to estimate average lint yield per acre to evaluate yield effects of PGR treatments.

UNDERSTANDING THE RESULTS

image Figure 1. 2020 average cotton height by cotton variety and PGR regime.
  • The untreated control treatments averaged 67 inches tall at season end (Figure 1). Passive treatments were an average of 49 inches with 18 inches reduction and the aggressive treatments were 42 inches with 25 total inches in height reduction. This echoes the results from previous years.  
image Figure 2. 2020 average cotton yield by cotton variety and PGR regime.
  • Like 2019, 2020 was not a year where an aggressive PGR approach was needed at the Bayer Learning Center in Scott, Mississippi. This is seen in both the height data and yield results; plots were generally shorter, and the untreated controls had higher yields than historical averages (Figures 1 and 2). 

  • On average across all cotton varieties, both PGR regimes improved yields in this trial by approximately 300 lbs/acre compared to the untreated control (Figure 2). 

image Figure 3. 2020 percent height reduction (compared to untreated control) of aggressive PGR regime on cotton varieties.
  • Earlier, more determinate cotton varieties were more sensitive to higher rates and earlier timings of PGR use as measured in percent height reduction. When comparing the untreated control to the aggressive treatments, cotton variety DP 2123 B3XF and earlier demonstrated greater response to PGR rates and timings as measured in height reduction with 42% reduction in height compared to 30% in the later, less determinate varieties (DP 2127 B3XF and later) (Figure 3). 

KEY LEARNINGS

  • Correct PGR use is essential to optimize the growth habit of modern cotton varieties.  

  • Earlier maturity varieties can be more sensitive to PGR applications compared with later maturity cotton varieties. Therefore, rate and timing of early applications are more important for later maturity cotton varieties for obtaining the needed growth control. This is particularly true in high fertility environments that favor vegetative growth. 

  • Plant growth monitoring and understanding historical varietal response to PGR application can help determine PGR application decisions.  

  • These data can be useful in considering the stress tolerance associated with cotton products. Typically, cotton varieties that are more sensitive to PGR applications can be more sensitive to stress and should be considered when determining field placement. Cotton varieties that are less sensitive to PGR applications are somewhat more stress-tolerant and can typically be planted into more stressful production systems. 

  • Consult your local Bayer representatives for more information about Deltapine® cotton variety placement and management for the 2021 season. 

 
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January 20,2019

Response of Deltapine® Cotton Varieties to Plant Growth Regulator Regimes - 2019 

 

TRIAL OBJECTIVE

  • The plant growth regulator (PGR) mepiquat chloride benefits cotton production by helping to balance vegetative versus reproductive growth. The appropriate rate and timing of PGR applications are essential to the management of cotton varieties in the coastal U.S.

  • Each season a new set of candidate cotton varieties is introduced through the Deltapine® New Product Evaluator (NPE) program.

  • The primary objectives of this study were to:

    • Evaluate the growth habit of new cotton products in comparison with existing Deltapine® cotton products.
    • Evaluate the response of the new candidate varieties to mepiquat chloride application in three different application regimes.

 

 

RESEARCH SITE DETAILS

Location Scott, MS     
Soil Type  Silt loam - mixed  

Previous
Crop
Corn    
Tillage
Type
Conventional  


 
Planting Date 5/17/19    
Harvest Date 10/9/19  

Potential Yield
 (lbs/acre)
2000    
Seeding Rate
(seeds/acre)
41,000

 
  • This study was set up to encourage excessive vegetative growth due to strong background fertility levels, the previous corn crop, irrigation, and relatively high rates of nitrogen fertility (120 lb/acre of actual nitrogen applied as 28% liquid UAN in-furrow at layby). 
  • Deltapine cotton products tested included Bollgard II® XtendFlex® cotton (B2XF) and Bollgard® 3 XtendFlex® cotton (B3XF). Bollgard II XtendFlex cotton provides tolerance to dicamba, glyphosate, and glufosinate herbicides and protection from cotton feeding insects. Bollgard 3 XtendFlex cotton has 3 modes of action to protect against cotton pests and triple stacked herbicide tolerance to glyphosate, glufosinate, and dicamba. 
  • All other agronomic inputs (weed control, insect control, and irrigation) were per local standards for each treatment.
  • Trials were planted in strip plots 8 rows by 240 feet long with a plot size of approximately 0.15 acre.
  • Three application regimes of mepiquat chloride (standard 4.2% formulation) were applied as follows (Table 1):
    • An untreated check with no PGR applied.
    • Passively managed regime (representing older growth management methods) – three application rates and three timings totaling 38 oz/acre applied with delayed early application on July 14, 2019 at a reduced rate.
    • Aggressively managed regime – three applications at maximum label rates at three timings totaling 48 oz/acre applied.
  • Growth characteristics of new Deltapine cotton products were evaluated as follows:
    • End-of-season plant height indicating the growth nature of the new product.
    • Height reduction from either the passively or aggressively managed treatments versus the untreated check.
    • Evaluation of the effects of the PGR treatments on yield.

 

UNDERSTANDING THE RESULTS

image
  • Varieties with a relatively high amount of height reduction are likely more sensitive to PGR applications and generally require less aggressive management. Understanding the nature of each cotton product helps in both proper placement and management decisions.

  • The tallest plants in this experiment were from the untreated plots and averaged 70 inches tall at the end of the season (Figure 2A). This is in contrast to 2018 where the tallest plants ended the season at 89 inches tall (Figure 2B). Compared to 2018, the environmental conditions of 2019 did not favor strong vegetative growth, resulting in less need for growth control.

  • A range of response (in height and height reduction) to PGR application was observed across this experiment (Figures 2A and 3). Several of the cotton varieties showed different levels of susceptibility to PGR application rates and timings.

image
image
image
  • When measured as a percent height reduction with similar rates and timings of PGR as were used in previous years of this study, a similar range of response was observed across cotton products with some products showing greater response to growth control (Figure 3).

  • The aggressive regime utilized the maximum labeled rate of 48 oz/acre split into three applications of 16 oz/acre. The earlier timing and higher application rates offered more power in growth control for some of the tested cotton varieties. Environmental conditions did not favor strong vegetative growth in 2019, resulting in some varieties experiencing yield loss with the aggressive PGR regime compared to the passive PGR regime.

image
image
  • As compared to previous years, cotton yield was considerably higher in all treatments in 2019.  Averaged across all products, the untreated plots yielded 1335 lb lint/acre (Figure 4A).  This contrasts with similar work in 2018 where the untreated plots averaged 653 lb lint/acre (Figure 4B). While environmental conditions were not conducive to excessive vegetative growth in 2019, they were ideal for boll retention and, when coupled with good harvest conditions, led to higher yields. 

  • Across all tested cotton products, the passive PGR application regime increased yield by 370 lb lint/acre over the untreated plots (Figure 4A).

  • The aggressive regime increased yield over the untreated plots by 218 lb lint/acre but were 152 lb lint/acre lower yielding than the passive regime (Figure 4A).

image
  • In 2019, earlier cotton maturities (DP 1725 B2XF brand and earlier) had a reduction in yield potential in the aggressive PGR applications compared to later maturities (Figure 5). 
image
  • As represented in Figure 6, all plots in this trial produced relatively high yields with the lowest recorded yield being 1100 lb lint/acre and the highest yield recoded being approximately 2000 lb lint/acre.

  • As in previous years, the treatment resulting in the tallest plants (greater than 60 inches) in the trial was the lowest yielding, while the plants in the higher yielding plots were between 40 and 60 inches at the end of the season.

  • Contrasting to previous work, some of the more aggressively managed plots were lower yielding as compared to those less aggressively (passively) managed.  End-of-season plant height less than 40 inches typically was associated with reduced yield as compared to the plots with an end-of-season height between 40 and 60 inches.  

  • 2019 was a year where PGRs could have been overused (as in some of the aggressively managed plots) and continues to point out the need for variety characterization, proper/timely scouting, decision making, and PGR applications.

 

KEY LEARNINGS

  • Both the NPE candidate cotton products and current commercial Deltapine® cotton products had high yield potential in the Scott, MS location during 2019.

  • Correct PGR use is essential to optimize the growth habit of modern cotton products. 

  • Newer cotton products are typically more aggressive in growth habit than older ones, making the need for timely monitoring and growth control application critical to the success of a cotton field. As much as a two-fold difference in growth response to PGR applications was observed across the tested cotton products in 2019.  

  • Plant growth and monitoring are the best tools for use in making the decision to use a growth control application with historical varietal response being an additional consideration. 

  • Consult your local Bayer representatives for further information about Deltapine product placement and management for the 2020 season.

 

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