Impact of Treated Wastewater Irrigation on Soil Chemical Properties, Potato Yield, Tuber Quality, and Heavy Metal Accumulation under Semi-Arid Conditions

Abstract

Treated wastewater is becoming a source of water for agriculture in arid and semi-arid regions where freshwater supplies are scarce. The aim of this study was to assess the effects of wastewater-treated irrigation on the water quality, soil chemical properties, growth and yield of potato (Solanum tuberosum L.), tuber quality, microbial contamination, and accumulation of heavy metals under field conditions in Al-Shuwaija, Wasit Governorate, Iraq. Randomized complete block design (RCBD) with two irrigation water sources (river water and treated wastewater) was used. Standard laboratory methods were used to analyze the water, soil and plant samples, and analysis of variance (ANOVA) at p ≤ 0.05 was used to assess the effects of the treatments. Both treated wastewater and river water were found to have significantly higher electrical conductivity, TDS, COD, BOD, total nitrogen, sodium, chloride, bicarbonate, sodium adsorption ratio, sodium percentage, and cadmium and nickel concentrations than treated wastewater. The use of treated wastewater for irrigation increased the soil fertility by raising both the organic carbon and organic matter, cation exchange capacity, total nitrogen, and nutrient availability, and increased soil salinity and the level of trace metals. Irrigating potato plants with treated wastewater resulted in better vegetative plant growth, such as height, biomass, and number of leaves. River water irrigation, however, produced significantly more tubers, weight of tubers, total yield, marketable yield, and marketable yield percentage. The quality parameters of tubers, such as dry matter, starch, and specific gravity, were lower under TW irrigation. In addition, treated wastewater resulted in higher Cd, Ni, Pb, Cr, Zn, and Cu content in tubers and higher counts of coliform bacteria and Escherichia coli in treated wastewater. Hence, treated wastewater can be used as an alternate source of irrigation water, but it must be monitored for salinity, microbial contamination, and heavy metal accumulation.