Abstract

The present study aimed at identifying the correct nitrogen and phosphate fertilization for the maximum productivity of Jatropha curcas plants. The study was carried out at the experimental field of the Ipameri Campus of the State University of Goiás. Three-year-old physic nut plants under full production were used. After analysis of the soil classified as Oxissol, pH correction was performed in accordance with technical recommendations for the species. The experiment followed a randomized block design with a 4 × 2 factorial arrangement [four doses of N (0, 100, 200 and 300 kg/ha) and two levels of phosphate fertilization (0 and 50 kg/ha). Fertilization was made in semicircle following the crown projection, 20 cm away from the stem. The lower leaf concentration of phosphorus in plants treated with 50 kg ha^-1 in relation to plants fertilized with phosphorus shows there was no deficiency in the plants that did not get phosphorus and possibly the 50 kg ha^-1 represented the excess of phosphorus due to the high content of organic matter. However, the high organic matter was not sufficient to meet the demand for nitrogen due to the high demand for J. curcas for this nutrient. Seed productivity presented a significant increase in relation to nitrogen fertilization. For 3-year-old plants cultivated at a spacing of 4 × 2 m, a fertilization of 81 kg ha^-1 is thus recommended.

Key words: Biofuel, mineral nutrition, growth, nitrogen, phosphorus.