Monitoring Of Nitrogen In SOIL Solution and In Orange Xylem SAP For Fertigation Management.

The citrus industry is a great important segment for the socio-economic structure in Brazil, once Brazil is the largest producer of orange. Fertigation is a technique that is expanding in the scenarios of Brazilian citrus. The application of fertilizers, especially nitrogen, by fertigation, is generally accomplished through preset doses without adequate monitoring the nutritional status of plants and the soil solution. There are techniques for monitoring nutritional status and soil fertility that have great potential for use in irrigated citrus, such as analysis of soil solution and xylem sap. In this sense it was aimed to evaluate the sensitivity of the analysis results of the orange sap and soil solution as the nitrogen applied by fertigation. The experiment was conducted in the municipality of Reginópolis-SP- Brasil in a orchard of Valencia sweet orange trees budded on Swingle citrumelo with 8 years old, during the period from September 2010 to August 2011. The experimental design was a randomized block design, with five treatments and four replications. The treatments consisted of five doses of N and K₂O, 0%, 25%, 50%, 100% and 200% (based on the conventional recommendation).  To assess the nutritional plant status and nutrient dynamics in soil, there were carried out a chemical analyzes in the leaf, xylem sap and soil solution. The concentrations of N-H₄- and N-NO₃ in the xylem sap and soil solution increased with the increasing levels of N. N-NO₃ concentrations in the xylem sap and soil solution have a strong positive correlation (0.82 **). The results of chemical soil solution and xylem sap were sensitive to the N doses applied.