Using Plant Growth Regulator in Oats Grown for Grain Back »

Written collaboratively by David Karki and Anthony Bly.


South Dakota Oat Production

South Dakota (SD) is a major oat producer in the nation. In 2016, the state ranked number one for oat grain production with more than nine million bushels harvested from 110,000 acres. The average oat grain yield for the state’s 2016 growing area was 82 bu/a. This has not only increased interest in oat among SD crop producers, but also with private industry such as General Mills Inc., a leading multinational consumer food manufacturer. Amid growing local interest from different sectors in producing food grade quality oats, the importance of management guidelines for efficient crop production cannot be overstated.

Among other small grain crops grown in the Region, oat is most prone to plant lodging when faced with high winds. In order to counter this issue, there has been an emerging interest in using plant growth regulator on oats. Plant growth regulator can be used to reduce plant height and increase stem diameter to prevent severe lodging.

Growth Regulator Research

With growers’ interest emerging, SDSU Extension and research faculty teamed up and initiated a study in 2016 in Northeast SD to evaluate the effects of plant growth regulator. The study was conducted at the SDSU Northeast Research Farm (NERF) near South Shore, SD. Along with growth regulator, another variable, nitrogen rate was added to the study. A total of five nitrogen rates (80, 100, 120, 140, and 200 lbs/a) were used with an additional ‘control’ treatment in the study which did not receive any nitrogen. The pre-study soil test results however showed that the field had 64 lbs/a of nitrogen. Therefore, this study treated 64 lbs/a nitrogen as ‘control’.

Urea was applied to the field on April 13th and planted the next day to oat the variety ‘Horsepower’. The herbicide Bronate was tank-mixed with growth regulator Palisade (Active ingredient- 12% trinexapa-ethyl) and applied on June 7th (Bronate at 13 oz/a; Palisade at 14 oz/a).

Observed Results

Plant Height
Plant height was affected by both nitrogen rates and growth regulator. Plant height ranged from 32” (control plot with palisade applied) to 38.3” (200 lbs/a N with no palisade applied) which was expected. However, contrary to expectations, no effects of growth regulator on lodging were observed. On the whole trial, only two individual plots had lodged plants which could be due to drier and cooler weather conditions when plants were at early vegetative stage and much drier later in the season. Further, the tested ‘Horsepower’ variety is considered one of the shorter SD varieties. The interaction effects of nitrogen rate and growth regulator were non-significant for plant height.

Grain Yield
Grain yield did not show significant difference for growth regulator, however, applied nitrogen had highly significant effects on grain yield (Figure 1). The interaction effect of nitrogen rate and growth regulator showed significant effects on grain yield.

Due to non-significant statistical effects of growth regulator, the yield was averaged across growth regulator treatment to assess the yield response to applied soil nitrogen (Figure 2). Applying more nitrogen beyond 120 lbs/a did not show much of a response as only 3 bu/a were gained when nitrogen was increased to 200 lbs/a (e.g. 157 bu/a for 120 lbs/a N vs. 160 bu/a for 200 lbs/a N). Yield to applied nitrogen ratio was about 75% when the nitrogen response ceased to show effect on grain yield.

Conclusion

The preliminary results from the study show that further studies on nitrogen recommendation for oats could be valuable for oat growers in SD. The study was extended into 2017 growing season as well and the results are being collected and analyzed at the present time.  



Figure 1. (Above) Oat yield response to applied nitrogen and growth regulator ‘Palisade’.
 


Figure 2. (Above) Oat yield response to applied soil nitrogen.
 

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