Adubação nitrogenada como atenuador dos efeitos da salinidade da água de irrigação utilizada para produção de forragem no semiárido

Abstract

The quality and quantity of agricultural crops are under continuous and serious threat of several abiotic stresses, with salinity being one of the most important. Salinity affects the metabolism of plants by primary effects through water deficit, ionic toxicity and nutritional imbalance, in addition to the side effects that are oxidative damages. Studies carried out in the field demonstrate a positive effect of nitrogen fertilization on soil salinity and water used for irrigation. In this sense, the objective was to evaluate the effect of nitrogen fertilization and irrigation with saline water during the production of sorghum and millet in the Brazilian semi-arid region. The research was conducted, under field conditions, at UAST, Serra Talhada-PE. The experiment was carried out in a randomized complete block design, arranged in subdivided plots, with four replications, arranged in the 4 x 4 factorial scheme, referring for 4 irrigation blades (28, 36, 44, 52% ETc) and 4 doses (0, 100 , 200, 300 kg ha-1) of nitrogen, adopting the Sorghum + Milheto system, being sorghum the main crop. Seeding was carried out on April 7, 2017, placing 30 seeds per linear meter on the average, spacing 25 cm between sorghum and millet. The irrigation blades were based on the ETc, being obtained by the equation ETc = ETo x Kc (of the sorghum). Nitrogen fertilization consisted of 1/3 in sowing and 2/3 in coverage. At the end of the crop cycle, plant height, stem diameter, number of live and dead leaves counted, yield Green and dry mass was estimated, N-total, Na+, K+ and Cl- contents were determined. The data were submitted to analysis of variance and the variables adjusted to the regression model, using SAS Software. According to the results obtained in this experiment, it can be concluded that nitrogen fertilization and irrigation with saline water benefited the growth of the sorghum and millet crop expressed in height, stem diameter, number of lives and dead leaves, green and dry biomass. Nitrogen fertilization favors the absorption of N-total and potassium by plants, however, it inhibited the absorption of chloride and sodium ions in the same condition, that is, nitrogen attenuated the salinity effects of irrigation water. The consortium favors an increase in biomass production. There was greater accumulation of N-total and chloride in the shoot of millet when compared to sorghum crop.