Recovery of nitrogen (15N) from urea and cane trash by sugar cane ratoon (Saccharum spp.)

An experiment was carried out to evaluate how mineralized nitrogen from cane trash and urea nitrogen applied to the soil is utilized by sugarcane ratoon. The field experiment was carried out from October 1997 to August 1998 on a Paleudalf soil in Piracicaba, State of Sao Paulo, Brazil. Four treatments were established: (T1) application of a vinasse and urea mixture over the whole soil area covered with cane trash-N-15 (crop residue); (T2) application of a vinasse and urea-N-15 mixture over the entire soil area covered with cane trash (crop residue); (T3) application of a vinasse and urea-N-15 mixture over the whole area without cane trash; (T4) urea-N-15 buried in furrows on either side of the cane rows, with previous application of vinasse on the soil without cane trash. The experiment was installed in a randomized block design with four replications. Components of crop productivity; accumulation of nitrogen in the aerial part of the sugar cane ratoon; and the crop's use of N-15 nitrogen of urea and of mineralized cane trash were evaluated for each treatment. The plant development occurred in a 315 day cycle and was similar in both conditions, with and without cane trash. Ten-16 % of the total nitrogen accumulated in shots of sugarcane ratoon came from the fertilizer and an average of 4 % was absorbed from the mineralized N of cane trash. Mean efficiency of the utilization of urea nitrogen by sugarcane ratoon was 17 %, with no difference among treatments, and that of the cane trash 8 %. Cane trash nitrogen was available to the plant towards the late crop cycle.