Teor e acúmulo de nutrientes em folhas e frutos de pinhão-manso

Knowledge about the nutritional demand of a crop is essential for fertilizer recommendation. In this study nutrient concentration and accumulation in leaves and fruits of Jatropha curcas L. were measured and nutrient extraction by fruits harvested between the 1st and 4th year of cultivation were estimated. The study was carried out at the Paraiso Farm, iin Vicosa, Minas Gerais State. Four leaf and fruit samples, each one containing 15 leaves or 20 fruits were randomly collected from an area with 6.000 Jatropha curcas L. trees, all planted in April 2006, at a spacing of 4 x 2 m. Expanded leaves between the 6th and 8th leaf below the inflorescence were collected for analysis. Only normal leaves (without signs of nutritional deficiency, insect attack and/or diseases) were used. Fruits were collected at maturity (yellow husk). The sampled leaves and fruits were washed, dried, weighed, and had their nutrient content analyzed. The nutrient concentration in Jatropha curcas L. leaves were ranked in the following order: N > Ca > K > Mg > P > S > Mn > Fe > B > Zn > Cu; and in the fruits the order was: N > K > Ca > P > Mg > S > Mn > Fe > B > Zn > Cu. The N/K ratio was 2.3 in the leaves and 1.4 in fruits, which indicates that K requirements increase when the plant begins fruit production. Although P is only the 4th (in fruits) and the 5th (in leaves) most demanded nutrient by the crop, it should be supplied in higher amounts than those accumulated in leaves and fruits due to soil adsorption. This study suggests that high nutrient amounts are extracted at Jatropha curcas L. harvest, thus the crop requires adequate fertilization to avoid soil exhaustion along the successive cultivation years.