부산대학교 도서관

A field trial was carried out on Cuban Oxisol planted with coffee trees, (Coffea arabica L.) using three N-fertilizer sources (15NH4N03, (15NH2) 2CO and K15N03) under Pinus cubensis Griceb shade to estimate the N-balance in plant - soil - fertilizer system. The sources were applied at the rate 100 kg N/ha with the an enrichment of 5 % of 15N. At harvesting time, between 32.2 % and 41.4 % of the 15N, were taken up by the plants, according to the sources, with vegetative drop was returned to the system between 2.6 and 4.4 % of the fertilizer applied. About 0.4 % of N in ammoniacal form remained in the soil and the non-measured losses were between 53.6 and 64.3 % of the fertilizers applied.