Crescimento e desenvolvimento da mamoneira em função da irrigação com águas salinas e matéria orgânica.

Abstract

This study was carried out aiming to evaluate the effects of irrigation with saline waters, reproducing ion ratios found in produced water from Petrobras in Rio Grande do Norte, and incorporation of castor cake, as organic matter, on growth, development and production of castor bean, besides water and ionic balance in the soil-water-plant system, in greenhouse of UFCG. The experiment was installed in randomized block design, in 5 x 2 factorial, with five levels of water salinity (0.2, 0.8, 1.6, 2.4 and 3.2 dS.m"1, at 25 °C) and without and with addition of castor cake (100 g) in substrates, resulting in ten treatments with three replications. The pots were filled with soil material from Carnaubais - RN, and fertilized with nitrogen, phosphorus and potassium. The percentage of germination and velocity of emergence decreased 5.72 and 7.71% per unit increment of electric conductivity of irrigation water (ECw), due to irrigation waters salinity, and were 40.8 and 26.6% higher in treatments without castor cake. During growth and development phase, a negative effect in plants by addition of cake was observed in the initial phase, with decrease of 22.8% in plant height, 9.3% in stem diameter and 23.8% in leaf area, 40 days after sowing (DAS); and for the salinity increases, possibly associated to the fermentation of castor cake in soil, after 80 DAS the decreases per unit increment in ECw were 6.56% in plant height, 5.69% in stem diameter and 18.15% in leaf area. As propagation of the effect of growth and development phase, unit increment in ECw promoted decrease of 14.58% in number of fruits, while addition of castor cake reduced the value of inflorence emission by 6.5%. The volume of water consumed was reduced by salinity of irrigation water, with decrease of 9.54% per unit increment in ECw. It was concluded that the increase of the salinity in irrigation water promoted significant negative effects in germination, growth and development of castor bean and raised the ECse and soil pH, reflecting in water consumption and yield of the crop. While the castor addition of cake caused damage to the crop in its initial phase.