Short-term changes in soil properties due to sanitary wastewater irrigation used as a potassium source

Abstract Irrigation with wastewater is an agricultural practice used to supply plants with nutrients that can reduce the nutrient load impact on fresh water sources and save conventional water sources. However, the physical and chemical properties of soil can be altered according to specific wastewater characteristics. This study aimed to investigate short-term changes in soil physical and chemical properties after irrigation of cotton with preliminary treated wastewater (PTW) and tertiary treated wastewater (TTW) as potassium sources in the semi-arid region of Minas Gerais State, Brazil. A randomized complete block design (RCBD) with four replications and five treatments was used: a combination of two wastewaters (PTW and TTW) as potassium topdressing sources and two equivalent doses to 40 and 60 kg K 2 O ha -1 , as well as a control treatment with a conventional mineral fertilizer. After the first soil sampling, the liming, NPK fertilizer, urea and potassium chloride treatments increased the base saturation and electrical conductivity up to 0.4 m soil depth. Wastewater potassium sources did not promote chemical excesses in the four soil depths evaluated, although the sodium content increased up to 0.6 m depth with 60 kg K 2 O ha -1 via TTW. The same dose (60 kg K 2 O ha -1 ) via PTW decreased the soil pH in the top 0.2 m and the water-dispersible clay (WDC) level up to 0.6 m depth due to the better chemical balance of this wastewater. In general, it is recommended to use PTW when providing 60 kg K 2 O ha -1 in topdressing