Temporal Variation in Leaf Nutrient Concentrations of Irrigated Jatropha curcas under Nitrogen Fertilization

Abstract

Cultivation of Jatropha curcas L. has been promoted because of its potential as a non-edible oilseed crop for clean-energy applications and its adaptation to arid and semi-arid environments. This study evaluated temporal variation in foliar macro- and micronutrient concentrations in irrigated J. curcas under different nitrogen fertilisation doses. The field experiment was conducted in a semi-arid region of north-eastern Brazil using a randomised block design with split plots. Four nitrogen doses were evaluated, and post-treatment foliar sampling was conducted at 145 and 271 days after standardisation pruning; the 75-day sampling was used only as a pre-treatment baseline covariate. Healthy, mature leaf blades free from pest and disease damage were collected for nutrient analysis. Nitrogen, phosphorus, potassium, calcium, magnesium, iron, zinc, and manganese were determined. Nitrogen fertilisation did not significantly influence the foliar concentrations of the evaluated macro- or micronutrients under the studied conditions. Sampling period significantly affected the macronutrients and the foliar concentrations of iron and zinc, whereas manganese did not vary significantly with sampling period. Across the sampling periods, macronutrient concentrations followed the order N > Ca > K > Mg > P, while micronutrient concentrations followed Fe > Mn > Zn. These findings indicate that temporal variation in leaf nutrient status was more evident than the response to the tested nitrogen doses during the evaluated period.