Physicochemical changes of semiarid soil submitted to treated wastewater, with and without cultivar

Abstract

This work evaluated the changes in physicochemical attributes in semiarid soil submitted to domestic sewage submitted to anaerobic treatment, in the presence or absence of the cultivar. The experimental unit was set up in the rural area of Ouro Verde, municipality of São Domingos, state of Bahia, Brazil. Five treatments were tested by diluting wastewater and supply in the percentages 0 %, 25 %, 50 %, 75 %, and 100 %. Soil samples were taken at depths of 0 - 35 cm (P1), and 35 - 70 cm (P2) from the sampling units with cultivar, control units without cultivar, and the unit without treatment (white). The cultivar was of corn (Zea mays L.), of the family Poaceae, which has a relatively short cycle (60 - 120 days). At the end of the experiments, after the harvest, the control units presented average Ca, P, K, and OM percentages from 5% to 66 % higher than white, while in the sample units, the percentages were 4% to 44 % higher, due to consumption by the cultivar. The contribution of TKN in the sampling units was the minimum sufficient for consumption by the cultivar. Compared to the control units, the sampling units presented Na, SAR, PST, and EC percentages higher by 35 - 113 % in P1, and by 29 – 456 % in P2, which indicates a higher consumption of cation by the cultivar in P2; change of ion distribution in the soil cation exchange site; as well as predisposition of the soil to sodification (increase of PST) and salinization (increase of EC). Consequently, the application of treated domestic effluents for agricultural activity, although it adds nutrients to the soil, has negative effects due to the increase in soil sodicity and salinity.