FALL APPLICATIONS OF MCPA TO IMPROVE TILLER SYNCHRONY AND REDUCE LODGING IN WINTER-WHEAT

Poor developmental spike synchrony in wheat (Triticum aestivum L.) can reduce the effectiveness of chemical treatments keyed on reproductive events. The broadleaf herbicide (2-methyl-4-chlorophenoxy) acetic aci d (MCPA) can be used to retard the development of wheat tillers if app lied to winter wheat in the fall prior to the initiation of tiller pri mordia. Fall applications of 0.5 kg ha-1 MCPA were sufficient to reduc e the tillering rate by 20-30% while providing a slight, but statistic ally nonsignificant, increase in yield. Significant increases in kerne ls spike-1 were observed in the MCPA treatments. The effect of MCPA on kernels spike-1 could be modulated by nitrogen fertility and planting density. A linear relationship between spike. number m-2 and planting density could be observed with MCPA treatments. Reductions in total n umber of spikes m-2, but an increase in kernels spike-1, resulted in s ignificant improvements in tiller synchrony. Improved tiller synchrony is important in optimizing chemical treatments where applications are based on the developmental stages of the spike. Significant reduction s in plant height and subsequent reductions in lodging under high nitr ogen fertility and high plant populations were observed with MCPA trea tments.