Irrigação com água salina e adubação nitrogenada na cultura do girassol.

Abstract

The use of technology in the proper management of low quality water and nitrogen, become indispensable practices in the cultivation of oil as an alternative renewable energy source, socially just and environmentally sound economically viable. Given the context, we sought to study the components of growth and production yields, dry matter and nutritional status of sunflower as affected by salinity of irrigation water and nitrogen fertilizer levels in research experiments conducted by two tests under conditions of field at the site Macaquinhos property, located 8 km south of the municipality of San Remigio, PB, in the periods from November 2011 to February 2012 and November 2012 to February 2013. It used a scheme in randomized block split plot, testing salinity levels ranging from 0.15, 1.5, 2.5, 3.5 and 4.5 dS m-1 and four nitrogen levels corresponding to the first test (40, 60, 80 and 100 kg ha-1) and the second test (60, 80, 100 and 120 kg ha-1), 5 x 4 factorial design with 3 replications and 30 crop per plot. Nitrogen fertilizer was applied as treatments and potassium with 80 kg ha-1 of K2O in installments three times, and third applied in the furrow before sowing and 2/3 split coverage applied in third at 20 and 1/3 to 40 days after emergence, and fertilization with phosphorus (80 kg ha-1 P2O5) and boric acid (2 kg ha-1) were made in the foundation. Watering was carried out every two days by means of a drip irrigation system, drip tape using a flow rate of 6.0 L h-1. The depth of irrigation water was calculated based on Kc crop and reference evapotranspiration (ETo) estimated by class A pan method, installed in UFPB, Campus II, Areia PB-meteorological station, located at 8 km away straight from the experimental area. The results were evaluated by analysis of variance test for 'F' at the level of 0.05 and 0.01 probability and in cases of significance, conduct analysis of linear and quadratic polynomial regression using the statistical software SISVARESAL. The growth of sunflower stem diameter, height, number of leaves and leaf area, production and productivity of the achenes, the oil yield, dry biomass of the chapter without achenes and the dry mass of the plant in all intervals from 15 to 90 DAE, with the exception of dry biomass at 30 DAE, were negatively affected by salinity of irrigation water from the ECa 0.15 dS m-1 and positively affected by increased nitrogen fertilization for all variables and all ranges. The salinity of irrigation water adversely affects the content of P and K to 75 to 45 and 75 positively and N content at 30 and 90 DAE and the variation of nitrogen fertilization affects the N content at 15 and 90 and the negatively P content at 60 and 90 DAE. Among the variables, leaf area at 15, the dry weight of the plant at 15, 30, 45 and 75, the N content at 45, 60 and 90 DAE, the dry matter of the chapter with achene and head diameter of sunflower, are the most sensitive to increasing salinity of irrigation water and oil content in sunflower achenes, is the variable most negatively affected with increasing doses of N.