Improving ryegrass‐clover pasture dry matter yield and urea efficiency with gibberellic acid

BACKGROUND The effects of spraying gibberellic acid ( GA 3 ) at 20 or 30 g ha −1 , with or without application of urea, on pasture dry matter ( DM ) yield, herbage nitrogen (N) concentration and feed quality were investigated in 2011 and 2012 for managed pastoral systems in New Zealand across a range of sites, in both autumn and spring. RESULTS On the Waikato site (autumn and spring, 2012), and at all five sites in 2011, liquid urea applied with GA 3 at 20 or 30 g ha −1 consistently produced significantly higher pasture shoot DM yield, relative to liquid urea alone. Application of GA 3 alone reduced feed quality by lowering metabolizable energy, crude protein and organic matter digestibility values. However, a reduced feed quality was not observed when GA 3 was applied together with liquid urea. Liquid urea applied with GA 3 also reduced total N and nitrate‐N concentration in herbage, relative to liquid urea applied alone. CONCLUSION Application of GA 3 together with liquid urea provides an opportunity for the strategic use of urea to meet both production and environmental goals. © 2014 Society of Chemical Industry