DISTRIBUTION AND CYCLING OF NUTRIENTS IN PINUS-RADIATA AS AFFECTED BY PAST LUPIN GROWTH AND FERTILIZER

Abstract

The effect of past lupin (Lupinus arboreus Sims) growth and the application of a balanced mixture of fertiliser on the distribution and cycling of nutrients (N, P, K, Ca and Mg) in a 14-year-old stand of Pinus radiata D. Don growing on a stabilised coastal sand dune was studied. Tree growth continued to respond to fertiliser (960 kg ha-1 N applied during the first 10 years) but growth in the lupin treatment (where lupin was effectively absent since the stand was 5 years of age) was similar to that in the control. Biological N2-fixation by lupin growing under the developing pine canopy was estimated to average at least 80 kg ha-1 year-1 over 5 years. Ecosystem-N (exclusive of roots) in the co..