Effects of nitrogen and lime on growth of Leucaena leucocephala cv. Cunningham on a red-yellow podzolic soil in south-eastern Queensland

Abstract

Field and glasshouse experiments were conducted on an acidic red-yellow podzolic soil of low nitrogen status from south-eastern Queensland to examine the use of nitrogen and lime in promoting leucaena growth. In the field, application of 25 kg nitrogen ha-l at planting increased shoot dry weight by 77, 88, 52 and 51% at weeks 5, 15, 32 and 52 respectively. Equivalent responses to lime (2.5 t ha-1) were 8, 3 1, 64 and 74% respectively. In the glasshouse, shoot, root and nodule dry weights were increased by nitrogen application rates of 50, 100 and 200 kg ha-1. Number, size and dry weight of nodules were suppressed at the highest rate (400 kg ha-1). Nitrogen concentration in youngest fully expanded leaves was increased to over 5% by nitrogen, and a critical nitrogen content of 4.5% (90% of maximum growth) is suggested. Inexplicably, lime application reduced shoot, root and nodule weights at high nitrogen applications. The apparent partial effectiveness of commercial leucaena Rhizobium and the implications of starter nitrogen and lime for leucaena establishment are discussed.