APPLICATION OF N-15-LABELED UREA TO SUGAR-CANE THROUGH A DRIP-IRRIGATION SYSTEM IN MAURITIUS

Nitrogen (N) fertilizer use efficiency by sugar cane in Mauritius rare ly exceeds 40%. Since drip-irrigation delivers water uniformly and dir ectly to the root zone with little run-off, application of N via the d rip-irrigation system could therefore provide a means of enhancing fer tilizer N use by sugar cane. A study was initiated in Mauritius to det ermine what benefits would accrue from applying urea (120 kg N per ha) to sugar cane through the drip-irrigation network. The data obtained showed that the efficiency of fertilizer N when measured at harvest wa s nearly doubled by supplying the N daily over 10 to 20 weeks by ferti gation. Increased yields of sugar or cane did not, however, accompany the improved N use efficiency. Furthermore, when N was applied through the drip-irrigation network, recovery of N at harvest did not accurat ely reflect N use efficiency.