Relatório de estágio integrado.Salinidade da água de irrigação e adubação nitrogenada no crescimento e produção da mamoneira BRS energia.

Abstract

The cultivation of the castor bean has been gaining importance and prominence in the Brazilian political and economic scenario seeking besides new sources of energy, income generation and job opportunity for small farmers, especially in semiarid region where evapotranspiration often exceeds rainfall causing the accumulation of high amounts of salts in the soil naturally through irrigation water which constitutes major obstacle to the production system. In this context, the objective of this study was to evaluate the vegetative, physiological and productive behavior of irrigated castor bean cv. BRS Energia with increasing water salinity and nitrogen, in a study conducted from October 2010 to February 2011 under protected cultivation at the Federal University of Campina Grande, PB using the statistical design randomized block in 5 x 5 factorial, with three replications. The treatments consisted of five levels of electrical conductivity (ECw) of irrigation water of 0.6; 1.6; 2.6; 3.6 and 4.6 dS m-1 combined with nitrogen fertilization of 50; 75; 100; 125 and 150 mg N per kg of soil. The salinity of irrigation water promoted reduction in height 11.2% in the initial stage (20 DAS) and in the development stage (80 DAS), in stem diameter of 8.9%; the number of leaves and leaf area 7.2 and 16.8%, respectively, with per unit increase in ECw, and on root biomass production (16.0%) and the stem (18.2%). Nitrogen fertilization favored the increase in the number of leaves at 80 and 100 DAS in approximately 8.2 % for addition of 25 mg of N per kg of soil. The interaction between salinity of irrigation water and nitrogen rate significantly influenced the biomass of castor bean, per unit decreases with increasing ECw ranged from 12.3 to 18.1% for the dry mass of leaves, from 18.1 to 19.8% for dry mass of cluster and 16.6 to 19.4% for dry mass of shoots when fertilized with doses of 50 and 150 mg of N per kg of soil, respectively; and when irrigated with water of 0.6 dS m-1 EC the biomass in leaf and shoot cv. BRS Energia had increased by 16.9 and 5.5% for each increment of 25 mg of N per kg of soil. Physiological variables leaf mass ratio and absolute growth rate, showed significant response to the salinity of the water. Production variables seed number, fruit number and weight of seeds per plant reduced respectively by 81.7, 79.4 and 88.6% when ECw of 0.6 and 4.6 dS m-1 were compared besides a variation in fruit weight per plant 4 of 18.1, 20.0, 19.4, 20.6 and 19.8% with unit increase in salinity of irrigation water when the plants were fertilized with doses of 50, 75, 100, 125 and 150 mg N kg-1, respectively. The nitrogen and phosphorus in leaves of castor bean BRS Energia presented linear increases with per unit increase in ECw of 14.18 and 11,0 %. The oil content in seeds increased with water salinity until Ecw of 1,22 dS m-1 in the lowest dose of N (50 mg N kg-1 soil), the maximum oil content observed being 55,35%. as been found, the compost is at the lowest dose (50 mg kg-1) increase in the oil content until the salinity of 1.22 dS m-1 obtaining the maximum oil content (55.35%).