Diagnostic leaf to evaluate the nutritional status of Jatropha

Folha diagnóstica para a avaliação do estado nutricional do pinhão-manso

ABSTRACT

The analytical determination of nutrient levels in recently mature leaves in order to diagnose nutritional status is based on the fact that leaves are metabolically active and more sensitive to variation in nutrients of the soil. In most of cases, there is a direct well known between foliar content and the development and yield of the plant. However, for a more accurate interpretation, it is essential to establish the index leaf. There are few published studies about Jatropha with contrasting results. In order to establish the index leaf, in adult plants, the macronutrient levels were evaluated in samples collected in experimental plots, in which doses of nitrogen and phosphorus were applied, in two parts of the floral branches (in the top and in the middle thirds); and in three positions of leaves of the floral branch (between the 1^st and 3^rd, 6^th and 8^th, and 13^th and 15^th leaves below the inflorescence). The location of the leaf on the plant significantly affects nutrient contents. Nitrogen, phosphorus, potassium and sulfur tend to have higher concentration in young tissues. Calcium and magnesium showed higher levels in the basal leaves of floral branches. Samples collected in the top third of plants (between the 6^th and 15^th leaves of the floral branch) are more sensitive to variations of nitrogen and phosphorus fertilization. Therefore, we indicate the 6^th to 15^th leaves of the top third plants as index leaves estimate nutritional status of Jatropha.

Key words:
leaf analysis; index leaf; nitrogen; phosphorus