ESTIMATE OF MINERALIZED ORGANIC NITROGEN IN SOIL USING NITROGEN BALANCES AND DETERMINING AVAILABLE NITROGEN BY THE ELECTROULTRAFILTRATION TECHNIQUE - APPLICATION TO MEDITERRANEAN CLIMATE SOILS

To be able to optimize the nitrogenous fertilizer rate applied to agri cultural crops, the soil's available N must be known, particularly tha t provided by the organic matter's N mineralization. The methodology p roposed to achieve this aim is based on determining the soil's mineral N balance. Many parameters were controlled in this endeavor: mineral N content at three depths (0-30, 30-70, and 70-140 cm), crop absorbed N, leached N and the soil's moisture content. A mineral N balance was established for two types of crop with different cycles: winter cereal (wheat) and spring-summer cereal(maize). Two irrigation systems were also compared. This method enabled the mineralized N to be accurately estimated. It likewise enabled a formula for estimating available N ba sed on the EUF technique.