Trash conservation measures associated with burnt and green harvested cane, and minimum tillage, are being adopted by canegrowers. These new management systems pose questions about how to apply N fertilizers. Experiments were conducted to evaluate the efficiency of fertilizer N uptake by the crop. Urea, labelled with 15N , was either broadcast or buried in three trash management systems: with and without trash after harvesting cane burnt, and with trash after harvesting cane green. The proportion of applied fertilizer-N recovered in a cane crop was 33% when labelled urea was buried, and 18% when broadcast. The presence of trash mulches from burnt or green harvested cane had negligible effects on the uptake of fertilizer-N. Of fertilizer-N applied, 25% was detected in soil 12 months after application, and there was no difference between burying and broadcasting urea. The fate of the lost fertilizer-N was not determined. Leaching did not appear to be a significant loss process in this gleyed podzolic soil, but ammonia volatilization probably occurred when urea was broadcast and it is suspected that denitrification accounted for the majority of the fertilizer-N losses.
Impact of pre-harvest burning versus trash conservation on soil carbon and nitrogen stocks on a sugarcane plantation in the Brazilian Atlantic forest region