INITIAL GROWTH of Physic Nut Affected by Phosphorus RATES.

Physic nut (Jatropha curcas L.) is a perennial and monoecious plant, belonging to the family Euphorbiaceae and its cultivation is a potential alternative to the production of vegetable oils with fuel purposes, since it does not compete with food production and can produce up to 2 Mg of oil per hectare. However, studies of culture management are still rudimentary and preliminary in Brazil, and there is a need to improve techniques for cultivation, especially on the fertilizer recommendation. For many authors, phosphorus (P) is the nutrient that deserves more attention in the early development of physic nut, so it is necessary to determine an appropriate P rate and that promotes a good initial growth. We aimed with this work to assess the effect of phosphorus fertilization on initial physic nut seedlings development planted in plastic pots containing 50 kg of a Red Latosol (an oxisol), which had a P content of 8 mg kg-1. The treatments consisted of five P rates (0, 50, 100, 150 and 200 mg kg-1) with four replicates. Soil of all treatments received fertilizer with micronutrients, nitrogen (80 mg kg-1) and potassium (80 mg kg-1) and the soil base saturation was corrected to 60%. The results of the regression analysis of evaluations performed 90 days after planting indicated a quadratic effect to the number of leaves, length of seedlings, stem diameter and SPAD index, corresponding respectively to the maximum values calculated of 31 leaves, 64 cm, 2.8 cm and 49.5. P rates that provided these values were respectively 137, 134, 143 and 143 mg kg-1 P. We concluded that the physic nut crop responds to fertilization and that P rates between 134 and 143 mg kg-1 may be recommended for its initial development.