Cultivo de milho sob irrigação com águas salinas e doses de esterco bovino.

Abstract

Corn cultivation exerts a great socioeconomic expression in the Brazilian scenario, being one of the main cereals cultivated in the Northeast region, which in addition to facing serious problems with scarcity of water resources, mainly in its qualitative aspect, also verified high levels of salts. The objective of this study was to evaluate the cultivation of maize irrigated with water of different saline levels under different doses of bovine manure. The experiment was carried out in a protected environment linked to the Agricultural Science and Technology Center (CCTA) of the Federal University of Campina Grande (UFCG), located in the city of Pombal, PB. The experimental design was a randomized block design, with a factorial scheme (5 x 4), related to five levels of electrical conductivity of the irrigation water (CEa), S1 water supply with CEa of 0.3 dS m-1, S2-CEa of 0.8 dS m-1, S3-CEa of 1.3 dS m-1, S4-CEa of 1.8 dS m-1 and S5-CEa of 2.3 dS m-1, combined with four doses of fertilization, being D1 without fertilization (control), D2-50% bovine manure, D3- 100% bovine manure and D4-125% bovine manure. Growth, gas exchange, chlorophyll a fluorescence, physiological indexes, and dry biomass were evaluated. Growth and dry matter at 30 DAS, and gas exchange, especially stomatal conductance and corn transpiration, are compromised by increased salinity of irrigation water, but this increase influenced a greater increase in chlorophyll a fluorescence and in physiological indices. Increased doses of bovine manure reduced the physiological indexes, but influenced a greater increase in gas exchange, growth and greater accumulation of dried corn phytomass. In the instantaneous efficiency in the use of the water, the manure with bovine manure only favored in a greater increment until the dose of 50%. Increasing doses of bovine manure can somewhat minimize the deleterious effects of salts on stalk diameter and dry matter of corn stalk and leaves at 30 DAS.