Deficiencies of macronutrient on the growth and biomass yield of castor bean cultivar Iris

Abstract

The objective of this study was to evaluate the effects of macronutrient deficiencies on the growth and biomass yield of castor beans (Ricinus communis L.) cultivar Iris. The experiment was carried out under greenhouse conditions. It was used a completely randomized design, with the treatments in a split plot arrangement with six replications for N, P and K, and three replications for Ca, Mg and S. The plots corresponded to treatments and sub-plots, the evaluations performed weekly right after the treatments started. Nutrient solutions containing all macronutrient and those from which one of these elements was omitted were the treatments used. Visual symptoms of deficiencies were observed in all treatments. The following determinations and measurements were made: stem diameter, plant height, axial root length and the shoot : root ratio. Plants were harvested at 91 days after the  treatments started, then various parts were separated. Visual symptoms of deficiencies were observed for each treatment with N, K, Ca, Mg and S being the first to show up and that of P being the last. Deficiencies of N, Ca, Mg and S were the most limiting for castor bean stem diameter as well as the plant height, whereas K and P had less effect. There is a close relationship between the plant height and stem diameter. The axial root length as well as the shoot : root ratio was not affected by the treatments. N, Ca, S and Mg deficiencies were the most limiting for the dry matter yield, being followed, in a decreasing order, by K and P, showing up the nutritional requirements of the castor beans ‘Iris’.