Disponibilidade de nutrientes e crescimento de porta-enxertos de citros fertilizados com fertilizantes convencionais e de libera？？o lenta

the slow release fertilizers are used to reduce the frequency of fertilization because provides gradually the nutrients to the plants. however the release of nutrients should be the same that nutrient demand by plants. the aim of this study was to evaluate availability of n, p and k and growth of two citrus rootstocks when slow release and conventional fertilizers were applied. two fertilizations systems in a commercial substrate were appraised (with controlled-release fertilizer and with only conventional fertilizers), two rootstock ('rangpur lime' tree and tangerine 'sunki' tree) and five sampling times (30, 60, 90, 120 and 180 days after the transplanting) with five repetitions and two plants per plot. the uses of slow release fertilizer increase stem diameter, leaves number, p contents in leaves of rootstocks and p and k disponibility in substrate, when compared with use of conventional fertilization.