Carryover Potential of Pyrithiobac to Rotational Crops on a Mississippi Black Belt Region Clay Soil

Abstract

Field studies were conducted on a Black Belt region clay soil to evaluate pyrithiobac injury to cotton and potential carryover to grain sorghum, soybean, and wheat. Pyrithiobac was applied PPI, PRE, POST at pinhead square, or POST at first bloom at rates of 70, 140, or 280 g ai/ha to cotton. Cotton injury was 7% or less at all rates and application timings. Cotton yield was not reduced by any treatment. The PRE application to cotton, averaged over rates, reduced yield of wheat planted in the fall compared to the POST pinhead square application or the nontreated check. Pyrithiobac at 140 g/ha applied PPI to cotton the previous year reduced soybean yield; at all other rates and timings no soybean yield reduction occurred compared to the nontreated check. Pyrithiobac at all rates applied PPI to cotton caused grain sorghum injury the following year. The 280 g/ha PPI application delayed grain sorghum maturity; however, this did not translate into a yield reduction.