The fate of fertilizer N in field studies in the volcanic Lesser Antilles with 15N-urea. (330)

Abstract

In the Lesser Antilles, recent replacement of old rural systems by intensive market gardening (MG) has led to a decrease of the soil organic matter (OM) content. A field experiment was designed on different types of soils (vertisol, ferrallitic soils, and andisol), to determine the effect on soil OM content of previous land use, either fallow (F) and pasture (P) or MG and banana plantations (B). The fate of 15N-urea applied to a maize crop was studied under the different combinations of soil type and previous land use history. Plant productivity of maize crops reflected N uptake, but not the N levels in soil OM. In the Lesser Antilles, soil OM does not limit plant productivity. However, immobilization of fertilizer N in soil (and thus a reduction of N losses) was positively linked to soil OM status. Losses, except for the andisol, were less than 30% of applied urea N, an observation which favours the use of urea in this humid tropical area.