NITROGEN DEPOSITION IN CASUARINA-EQUISETIFOLIA (FORST) PLANTATION STANDS IN THE DRY TROPICS OF SONBHADRA, INDIA

Periodic variations in the concentration, deposition and canopy impact of different forms of N on annual N deposition through rainfall throughfall and stemflow in 5 and 8 year old stands of Casuarina equisetifolia were studied. Throughfall and stemflow ranged from 70 to 76% and 5-6% of annual precipitation, respectively. The total N deposition by rainfall was 11.1 kg ha(-1) year(-1), and by throughfall was 13.6 kg ha(-1) year(-1) and 16.5 kg ha(-1) year(-1) in 5-year-old and 8-year-old plantations, respectively. The quantities of N deposited through stemflow in the two plantations were nearly identical, accounting for 1.6 kg ha(-1) year(-1). Observations of the monthly deposition of NH4-N, NO3-N, Kjeldahl-N and organic-N revealed that maximum deposition occurred in July and the minimum in September. Organic-N deposition was 17% less (5-year) than the rainwater content. Net deposition of N, as an effect of canopy, was 7-8.7 kg ha(-1) year(-1), which was added directly to the available nutrient pool of soil.