Gibberellic Acid Promotes Early Growth of Winter Wheat and Rye

Abstract

Winter wheat ( Triticum aestivum ) planting in Nebraska is recommended for mid Sep but summer crops are often harvested around Oct 1. Also, weather may delay planting. Could gibberellic acid (GA 3 ), a growth stimulant, overcome the delayed seedling growth from late planting? Irrigated field trials were planted from 2005 to 2010 applying GA 3 to wheat seed of cvs. Goodstreak and Wesley. In 2005, dip, spray and furrow GA 3 applications to seed were tested. Dip and spray gave similar results. Furrow application was calculated too costly. Further tests used seed dips. In 2006 to 2008 planting, wheat was planted about 15 Sep, 1 Oct and 15 Oct. Trials planted in 2007 and 2008 included winter rye ( Secale cereale ) cv. Rymin. Heights in mid Nov showed a reduction with later planting. When planted about 1 Oct and 15 Oct, the delayed growth of Goodstreak, compared to planting two weeks earlier, was fully overcome by GA 3 at 250 ppm. For Wesley, 1000 ppm GA 3 was needed to nearly overcome later planting. Rymin rye gave an intermediate response between the two wheat cultivars. Spring and summer heights were not affected by GA 3 . Spring biomass, yield and harvested seed germination showed no GA 3 effect. In later trials (planted in 2009 and 2010), the cytokinin 6-benzyl adenine (6BA) was added to GA 3 to stimulate tiller formation. In the 1 st year, 6BA at 2000 ppm depressed height, weight and yield without tiller promotion. Repeating the trial with lower rates (31 - 125 ppm 6BA) did not offer an additional advantage to GA 3 . The results indicate that seed application of GA 3 can overcome delayed growth resulting from delayed planting of winter wheat and rye under irrigation.