Physiological attributes of jatropha under different planting densities and nitrogen doses

Aspectos fisiológicos do pinhão-manso sob diferentes densidades de plantio e doses de nitrogênio

ABSTRACT

Nitrogen (N) fertilization associated with planting density is a practice that can improve the physiological aspects and consequently increase the yield of a crop. Thus, this study aimed to evaluate the effects of planting density and N levels on the physiological aspects of jatropha in the ‘Agreste’ region of Paraíba. Treatments consisted of four planting densities (833, 1,111, 1,666 and 2,500 plants ha^-1) representing the plots and five N doses (0, 40, 80, 120 and 180 kg ha^-1) corresponding the subplots. The effects of treatments on CO₂ assimilation rate, internal CO₂ concentration, transpiration, stomatal conductance, water use efficiency, instantaneous carboxylation efficiency and SPAD index were analysed. Except for stomatal conductance, the other variables were influenced by the interaction between planting densities and N levels. The association of the dose of 80 kg ha^-1 with a planting density of 2,200 plants ha^-1 provided adequate conditions for the production of plants with increased photosynthetic activity and efficient use of water.

Key words:
Jatropha curcas; gas exchange; nitrogen fertilizer; water use efficiency