Correlation between leaf nutrient contents and grain, oil and protein productivities in Jatropha curcas L

In plants, several chemical elements are found in different concentrations and formulations. Some of these elements influence each other, either through positive stimulation or inhibition. This study evaluated the correlation between nutrient contents and production components of Jatropha (Jatropha curcas L.). The experiment was conducted at the Federal University of Viçosa-MG, Brazil. A randomized block design with four replications was used. The treatments consisted of six Jatropha clones transplanted 4.5 years ago, from the municipalities of Janaúba and Bomfim, in Minas Gerais, Brazil. Yield was determined by harvesting the ripe and dried fruits, and the oil and protein contents in the grains were obtained by nuclear magnetic resonance. To determine nutrient contents, leaves were collected when the plants were in flowering, with yellow fruits and when the fruits were dry. There was a significant and negative association between grain yield and Mg content. Regarding foliar nutrient contents, the positive (r) significant correlations were between the following pairs: (N and S, r=0.554); (N and Cu, r=0.460); (P and Ca, r=0.420); (K and Zn, r=0.511); (K and Cu, r=0.506); (Ca and Mg, r=0.603); (Zn and Fe, r=0.662); (Zn and Mn, r=0.795); (Zn and Cu, r=0.574); (Fe and Mn, r=0.528) and (Mn and Cu, r=0.479); and the negative ones were between: (K and Ca, r=-0.596); (K and Mg, r=-0.673); (Mg and Cu, r=-0.506). Therefore, it was possible to prove the existence of nutritional interaction between some elements, as well as the effects on grain yields. This research will serve as a basis for studies to recommend fertilizer doses, plant improvement through nutritional efficiency, and studies in the area of biochemistry.