Trinexapac‐ethyl Affects Seed Production in Crimson Clover

Abstract

Core Ideas Crimson clover canopy height was reduced with trinexapac‐ethyl applications. Seeds m–2 in crimson clover was increased by trinexapac‐ethyl applications. Seed yield responses to trinexapac‐ethyl were dependent on spring weather conditions. Seed weight reductions were inversely proportional to trinexapac‐ethyl rate. This is the first study to document effects of trinexapac‐ethyl on crimson clover seed crops. ABSTRACT Trinexapac‐ethyl (TE), a plant growth regulator (PGR) and lodging‐control agent, increases seed yield in red clover (Trifolium pratense L.), but the effects of TE are unknown in crimson clover (Trifolium incarnatum L.) seed crops. The objectives of this study were to determine TE application rate and timing effects on crop canopy characteristics, seed yield, and seed yield components of crimson clover. On‐farm trials were conducted at two locations (Banks and St. Paul, OR) in 2012 and 2013 and at the Hyslop Research Farm near Corvallis, OR, in 2015 and 2016. Treatments were TE PGR application rates (0, 105, 140, 210, 280, 420, and 560 g a.i. ha−1) and two application timings (stem elongation, Biologische Bundesanstalt, Bundessortenamt und CHemische Industrie [BBCH] 32; inflorescence emergence, BBCH 51). Application of TE PGR reduced height of the seed crop canopy. Seed yield was increased in 2012 and 2013 with rates ≤280 g TE ha−1 when applied at the BBCH 32 timing. Seed yield increases attributable to TE ranged from 12 to 36%. However, no effects of TE application on seed yield were observed in 2015 and 2016, likely as a result of dry and warm spring weather. Seed yield increases in 2012 and 2013 were a result of TE‐induced increases in seeds m−2. Seed weight was reduced by TE application, and these reductions were inversely proportional to TE rate. Seed yield responses in crimson clover to TE PGR varied across years and locations, with seed yield increases occurring in wet and cool spring weather conditions.