Trinexapac-ethyl Winter Wheat (Triticum aestivum L.) Cultivar Evaluations with Variable Rates of Nitrogen

In the southeastern region of the United Sates, soft red winter wheat (Triticum aestivum L.) is grown in double-crop production systems. The plant growth regulator (PGR) trinexapac-ethyl is applied to improve wheat morphology by reducing height and increasing stem wall diameter, which can promote maximum yields. An experiment was conducted from 2014 to 2015 to evaluate the effects of trinexapac-ethyl with varying N rates on growth, lodging, and yield of five soft red winter wheat cultivars. Soft red winter wheat was treated with trinexapac-ethyl at 233 or 256 g ai ha-1at 60 d after planting, or as a split application of 128 g ai ha-1 60 and 108 d after planting. Nitrogen fertilizer at 112 or 168 kg ha-1 was applied at Feekes’ stage 3-4. Crop heights, spike counts per m2, and node length from the flag leaf to the base of the floral spike were collected 144 d after planting, with final yields, grain moisture, and test weight determined after harvest. There were no interactions for the main effects of PGR by nitrogen rate, PGR by cultivar, or cultivar by nitrogen rate. Trinexapac-ethyl at 256 at Feekes 4, or split applied at 128 g ha-1 at Feekes 4 and 7, significantly reduced soft red winter wheat height, and distance from the flag-leaf node to base of the floral spike as compared to the non-treated control. While there were no yield differences for trinexapac-ethyl treatments, height reductions and improved stem strength would reduce lodging that can often lead to crop failure.