Níveis de reposição da evapotranspiração da mamoneira irrigada com água residuária.

Abstract

The castor bean crop {Ricinus communis L.) in the Northeast of Brazil is nowadays considered as an alternative to produce biodiesel, and to develop the economy of the region and consequently the economy of the country. During November, 2005 and May, 2006 an experiment was installed at the greenhouse of the Agricultural Engineering Department in the Federal University o f Campina Grande, PB. The objective of this research was to study the effects and the potential of domestic wastewater on growth, development, production and nutrition of the plant as well as the soil chemical properties at the end of research. The plants grown in drainage lysimeters with 100 kg o f soil Eutrophic Argisoil during six months. The experimental design was in randomized block in 5x2 factorial scheme with 3 replications; each replication represented by mean of 2 plants during 90 days after sowing when a destructive analysis was made. After this period each plot was represented by one plant. 5 levels of reposition of the crop évapotranspiration - ETc were tested (0.60, 0.75, 0.90, 1.05 and 1.20 ETc) and 2 cultivars, BRS Nordestina and BRS Paraguaçu. The repositions of water were accomplished every 2 days. Contribution o f nutrients through wastewater favored the growth and development of plants, with improvements in the pH and water use efficiency (kg seeds/m3 water) and the oil content in the seeds, but was not enough to increase the production in levels of mineral fertilization. Continuous application of domestic wastewater, with EC 1.40 dS m"1 and sodium adsorption relationship - SAR 3.55 (mmol L~')1 / 2 , used in this research, along the time, can damage the structure and infiltration of water in the soil because of sodium. Castor bean irrigated with 60% of évapotranspiration had plant height, stem diameter, number of leaves and leaf area reduced in 32.47, 25.67, 47.41 and 105.00%, respectively. The BRS Paraguaçu had plant height significantly higher than the growth of BRS Nordestina, along the research. Under application of wastewater, all concentrations of micronutrients (CI, Fe, Zn, Cu, Mn and Na) contained in the roots were significantly higher in BRS Nordestina than the other one. Due to the redistribution for shoot, the leaves o f the castor bean contain larger rales o f macronutrients that the roots.