Irrigação com efluentes secundários no crescimento, produtividade e concentração de nutrientes no solo e na mamoneira.

Abstract

Castor bean cultivation, due to the high water and nutrients consumption, presents the ideal characteristics for receiving wastewater from treated sewage. Economics of fertilizer, recycling of water and nutrients and increased productivity are the main advantages of this practice. The objective of this study was to investigate, under field conditions, the effect of three configurations of domestic wastewater treatment, water supply and water depth on growth, yield, plant nutritional status and fertility of the soil at the end of the experiment. A randomized block design was used, with 4x2 scheme of factorial analysis with four replications, testing four types of water (Al - effluent from the UASB reactor + Polishing Pond; A2 - effluent from the Digester Decant + Anaerobic Filter + Stabilization Pond; A3 - effluent form the Anaerobic Filter + Stabilization Pond; and A4 - Urban water supply) and two water depths (100% and 120% Crops évapotranspiration). Water was applied using a drip irrigation system every three days. Plant height, stem diameter and number of leaves were evaluated at 29, 43, 57, 71 and 86 days after germination. Productivity of seeds, plant nutritional status and soil fertility were evaluated at the end of the experiment. Based on the results no significant difference in growth and seed production when using treated wastewater. Contribution of nutrients through wastewater favored the growth of plants, but was not enough to increase the production in appropriate levels of mineral fertilization and irrigation. For soil fertility, there was no significant difference in levels of P, K and Na for the three configurations of wastewater treatment. In general, there were no restrictions regarding the contents of P, Ca and Mg in the leaf of castor bean. The concentrations of N, K and Na in the leaf tissues were significantly equal for plants irrigated with treated effluent.