Nitrogen (N) fertilization is important for sugarcane crops, for both
agronomic and environmental reasons. Better use of N from fertilizer is
required for crop management, and in order to achieve it, adequate N nutrition
monitoring is necessary. Sap extract analysis is a sensitive technique that has
been adopted in other crops to tackle this objective, and can be used for
sugarcane. The aim of this study was to evaluate the behavior of N and the
response of sugarcane after N fertilization, using sap and leaf tissue
analysis. The study was undertaken in two experimental areas in 2012/2013
season, using ratoon cane, following application of 0, 50, 100, and 150 kg·ha-1 of N. The youngest visible leaves were sampled from sugarcane at five time
points between 0 and 150 days after fertilization, to evaluate the nitrate,
ammonium, and total N content of sap extract, and total N content of leaf
tissue. At the first sampling point (30 days after N fertilizer application),
mineral N in sap increased as a result of N fertilization in medium-textured
soil, and remained high until 120 days after fertilization in clayey soil. The
total N content of sap followed a similar behavior. Stalk yield was only
observed to increase in sugarcane grown in the clayey soil. Sap analysis proved
to be an efficient method for monitoring N status in sugarcane grown in
different soil types.