Stimulating Growth of Late-Planted Winter Wheat with Gibberellic Acid.

Introducing winter wheat as a rotational crop into irrigated cropping systems is limited by the overlap of irrigated wheat's optimal planting dates and preferred fall harvest dates. Can gibberellic acid (GA3) be used as a seed treatment to stimulate growth and establishment of late-planted winter wheat in the fall? Field trials were conducted at Scottsbluff. Seeds of wheat, Triticum aestivum cvs. Goodstreak and Wesley, were treated with 0, 125, 250, 500, or 1000 ppm GA3. Planting was on 20 Sep, 4 Oct and 16 Oct, 2006. Goodstreak height was promoted by GA3 applied at 125 ppm on all planting dates. Plants from seeds treated with 125 ppm GA3 and planted on 4 Oct were as tall as those seeded two weeks earlier. A similar height stimulation was observed with Wesley but GA3 was applied to seed at 500 ppm. In winter wheat, height stimulation was still observed in Mar 2007 but height stimulation was no longer observed in May or June. In May 2007, biomass was measured and showed that plants from seed treated with 1000 ppm GA3 and planted in mid-Oct had less fresh weight then untreated plants. At harvest, grain yields of GA3-treated Goodstreak and Wesley wheats were similar to untreated plants indicating no adverse effect. There was also no adverse effect on wheat seed viability due to GA3. Based on this first year of a GA3 rate-response study, growth stimulation by GA3 overcame the two-week delayed planting and could be used as a seed applied tool to allow winter wheat to establish itself with later planting.