Accumulation of ions in soil fertigated with dilutions of dairy effluents in the Brazilian semi-arid region

Wastewater is an alternative water source with the potential to guarantee agricultural productivity in semi-arid regions, where quantitative and qualitative scarcity is a limiting factor. This study aimed to analyze the effects of the application of dairy effluent dilutions on the alterations of sodium, calcium, magnesium, and nitrogen contents along the profile of an Ultisol cultivated with Cereus hildmannianus in the semi-arid region of Brazil. The experimental design used was a 5 x 5 factorial randomized block design with five dilutions of dairy effluent (T1 - only well water (WW); T2 - 0.1 x annual loading rate according to EPA (1981) (LW) plus WW; T3 - 0.2 x LW plus WW; T4 - 0.3 x LW plus WW; and T5 - 0.4 x LW plus WW) and five depths (0 to 0.10 m; 0.10 to 0.20 m; 0.20 to 0.30 m; 0.30 to 0.40 m and 0.40 to 0.50 m), with five replicates. Cereus hildmannianus cultivation lasted 240 days, and after this period, soil samples were taken to determine the contents of sodium, calcium, magnesium, and nitrogen. Fertigation using dairy effluent with up to 40% of the annual loading rate in Ultisol poses no risk of water and soil contamination by nitrogen leaching. Fertigation using dairy effluent in proportions of up to 20% of the annual loading rate poses no risk of soil degradation due to excessive accumulation of ions.