Effects of gibberellic acid application after anthesis on the feeding value of double-purpose rice (Oryza sativa L.) straw at harvest

This study was to investigate the effects of gibberellic acid (GA) application after anthesis on the feeding value of double-purpose (grains as human food and straw as animal roughage) rice (Oryza sativa L.) straw at harvest. Three japonica rice cultivars Huaidao 6, Nanjing 43 and Nanjing 46 in 2009 and Huaidao 6, Nanjing 43 and Yangfujing 8 in 2010 were cultivated in Nanjing under the same management of Jiangsu area. They were sprayed GA with 45 g hm−2 on the 15th d after anthesis in 2009 and on the 1st, 7th and 15th d after anthesis in 2010. At harvest, the feeding value related traits of rice straw, single panicle weight (PW) and 1000-grain weight were determined in 2 years. The fermentation quality related traits of fresh rice straw silage were determined in 2010. Nonstructural carbohydrates (NSC) and crude protein (CP) contents in rice straw were significantly increased by spraying GA, especially on the 15th d after anthesis, and the fermentation quality of rice straw silage was improved with the increase of NSC and CP contents. PW was also significantly increased by spraying GA after anthesis. The results indicated that spraying GA after anthesis could significantly improve the feeding value of straw and the panicle weight for double-purpose rice.

► We found that the contents of nonstructural carbohydrates (NSC) and crude protein (CP) were higher than the controls by spraying GA after anthesis.
► We found that the fermentation quality of fresh rice straw silage was improved with the increase of NSC and CP contents in rice straw.
► We found that single panicle weight (PW) was higher than the control by spraying GA on the 15th d after anthesis with 45 g hm−2.
► We found that the rice plant height was significantly higher than the control by spraying GA on the 1st d, but not on the 7th d and 15th d after anthesis.
► We concluded that spraying GA on the 15th d after anthesis significantly improved the feeding value of rice straw and single panicle weight.