Effect of gibberellic acid and nitrogen on winter growth of pasture
New Zealand Jour Agric Res 2(6): 1203-1210
The effects and interaction of gibberellic acid and N on pasture production, composition, and N levels were studied on a 2-year-old sward of ryegrass and white clover following mid-April application when the natural growth was slow. The application of gibberellic acid caused a rapid stimulation of growth, reaching a maximum within 4 weeks. Fertilizer N was slower acting, but its production equalled that obtained from gibberellic acid 6 weeks after application. Over the subsequent 6 months gibberellic acid depressed yields significantly, while slight N responses continued. No significant interactions were recorded. Gibberellic acid caused yellowing of the herbage and stem elongation up to the 1st mowing, 6 weeks after application. Yield responses and depressions of individual species resulting from treatment with gibberellic acid are presented. There was evidence of an increase in sward density within 6 weeks of application. Gibberellic acid caused increased yields of N (oven-dry material) up to 6 weeks after application. Samples taken 14 weeks after application showed a lowering of N yields from the acid treatment.