Urea Fertilization: Effects on Growth, Nutrient Uptake and Root Development of the Biodiesel Plant, Castor Bean (Ricinus communis L.)

Abstract

An indoor pot culture experiment was conducted in the growth chamber during the period of vegetative growth to evaluate the influence of inorganic nitrogen fertilizer in the form of urea on nutrient uptake, growth and root development of castor bean plant. The Nitrogen Fertilizer treatments imposed in the experiment were: Control (N0), no nitrogen and others at the rate and 60lb N/acre (N1), 90lb N/acre (N2) and 120lb N/acre (N3) respectively. Effect of higher nitrogen concentration indicated considerable increases in castor growth including vegetative growth and the plant components biomass. Elevated nitrogen fertilizer increased height and other morphological and physiological parameters (Leaf and petiole length, intermodal distance, root numbers) including the root, shoot dry wt, root/ shoot ratio, nitrogen  and crude protein content  in plants. Among the plant components, shoot, root dry weight and root shoot ratio had the greatest decrease under N deficiency, while root/shoot carbon ratio increased under N deficiency. No statistical difference was observed with treatments in shoot and root N% and shoot C% in plants although root carbon content was significantly higher with lowest nitrogen level compared to elevated levels. Significant increases of carbon content in plants at N0 showed some tendency of this crop to adjust with lower nitrogen levels. Also no statistical difference was observed in root and shoot N ratio, while the root and shoot carbon ratio was found significant at N0 compared to other treatments. However the concentration of carbon and nitrogen were found higher in shoot than root in all applied treatments. After harvesting the residual nitrogen effect in soil was also found significant with elevated nitrogen level compared with other treatments and control.