Alterations in calcium, magnesium and potassium contents in a red-yellow clay soil irrigated with a fish-culture effluent in a protected environment

Abstract

With the objective of observing the alterations in calcium, magnesium and potassium contents in a soil irrigated with fish-culture effluent in a vegetable house at UFERSA, an experiment was carried out using a totally randomized outline with four repetitions, with the treatments resulting in a factorial scheme (2x3x2): 2 irrigation waters (well - WL and fish-culture effluent - FE), 3 sources of phosphorus (natural phosphate - NP, soluble phosphate – SP, and control - CO) and 2 substrates (with organic matter – CM, and without organic matter - SM), resulting in 12 treatments. The soil used in the experiment was a red-yellow clay soil, and for the preparation of the substrate, bovine manure mixed in the proportion of 3:1 (soil / manure) was used as the source of organic matter. The experiment was conducted in pots with a capacity of 20 dm3 of soil, which were irrigated according to the treatments during 60 days. It was observed that the simple super-phosphate increased the exchangeable calcium in the soil in relation to the control. The contents of exchangeable magnesium and potassium in the soil increased with the addition of organic matter. It was also observed that the effluent increased the potassium content in the soil. Irrigation with fish-culture effluents is a viable alternative for the semi-arid conditions, since the majority of soils in that region is poor in nutrients, and the addition of nutrients present in the effluent works as a fertirrigation.