Effect of Prohexadione Calcium, a Plant Growth Regulator, on Peanut Growth and Yield in Arkansas, Georgia, Mississippi, South Carolina and North Carolina.

Prohexadione Calcium (ProCal) is a plant growth regulator which is commonly used on virginia market-type peanuts to manage excessive vine growth. The use of ProCal on runner market-type cultivars has been minimal. However, cultivars with more vigorous growth habit has renewed interest in growth regulators. Therefore, the objective of this research was to evaluate ProCal on virginia and runner market-type cultivars at reduced rates in small-plot and on-farm trials in a multi-state project. Application rates of ProCal were 508 g/ha (1X, labeled), 381 g/ha (0.75X), 254 g/ha (0.5X), and a non-treated check. Cultivar and treatment responses were evaluated based on canopy height, yield, grade, and return on investment (ROI). Plants treated with ProCal had greater row visibility and plants were often shortened when ProCal was applied, although response varied by location and year. ProCal did not significantly increase yield over non-treated in any small-plot peanut trial regardless of rate. Reduced rates of ProCal significantly increased yield in all of the on-farm trials compared to the non-treated check. Yield increases ranged from 453 to 731 kg/ha for all ProCal treatments compared to the non-treated check. The greatest ROI was seen in the 0.75X rate resulting in an increase in revenue of $210/ha. Based on the data from these trials, ProCal effectively reduced vine growth which supports previous work. Since there was a significant increase in yields and ROI in all of the on-farm trials and not in small-plot trials, it can be assumed that the growth and yield response to ProCal may be more pronounced in on-farm trials where soil characteristics vary across a field, affecting growth, digging, and yield potential. The response in small-plot trials might be masked due to the overall uniform soil characteristics and production management utilized.