Residual effect of castor cake on growth and yield of cotton irrigated with wastewater

This study aimed to evaluate the residual effects of organic fertilization with castor cake on growth, leaf nitrogen accumulation and yield of cotton plants irrigated with treated wastewater. Cotton plants were grown in pots with soil from a previous experiment with sesame plants submitted to the treatments which resulted from the factorial combination between five levels of castor cake (0, 2, 3, 4 and 5 t ha(-1)) and two types of irrigation water (potable water and treated wastewater) with three replications. At 30, 50, 70, 90 and 110 days after plant emergence, plant height, total leaf area and the nitrogen leaf content using a portable chlorophyll meter were determined. Crop yield was evaluated based on number of bolls per plant, mean weight of bolls, mass of hundred seeds, percentage of fiber and seeds, and oil content in seeds. A residual effect of castor cake levels on growth of cotton plant was observed. Irrigation with wastewater resulted in better plant growth and cotton yield; it also increased nitrogen content in leaf.