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Fertigation of crops with untreated wastewater predominates in developing countries. Use of wastewater for crop irrigation poses a potential risk of food chain poisoning with toxicants. However, direct and indirect interaction of wastewater with soil properties and crop productivity has been rarely investigated. The current work was, therefore, planned to quantify the impact of canal water, biologically treated and untreated wastewater on soil properties, growth, biochemical, nutrient turnover and yield of pea (Pisum sativum L.) plants. Seeds of P. sativum were sown in soil filled pots irrigated with five different water types [canal water (CW), biologically treated wastewater (BTW), 50%, 75% and 100% wastewater (WW50, WW75 and WW100)]. The plant samples were collected after 35 days for biochemical analysis, while yield parameters were recorded at maturity. The results revealed a significantly higher growth and yield of pea plants irrigated with BTW followed by WW50 and CW irrigated plants as compared to other wastewater treatment types. Application of untreated wastewater (WW75 and WW100) resulted in stunted growth due to decrease in total chlorophylls, carotenoids, activities of SOD and POD enzymes, and increase in lipid peroxidation (MDA and H2O2) as compared to CW, BTW, and WW50. Pre- and post-harvest soil analysis revealed that application of concentrated wastewater caused soil alkalinization and subsequently limited the nutrient absorption by P. sativum plants. Growth enhancement of P. sativum under BTW might be a direct consequence of balanced accumulation of nutrients owing to alteration of soil properties. It was concluded that wastewater must be treated biologically or diluted with 50% of fresh canal water before application to agricultural fields in order to maintain soil nutrient level and sustainable crop productivity in the areas with less availability of fresh canal water.

In developing countries, wastewater fertigation for crop cultivation is a common practice. The wastewaters being used include both untreated and biologically treated, although the former predominates the later. Biologically treated wastewater has certain advantages, but its direct and indirect interference with soil properties and crop productivity has not been systematically documented. The present study was aimed to investigate the effect of clean water, untreated and treated (biologically) wastewater on soil properties, growth and yield attributes of the mung bean (Vigna radiata L.). Pot experiments were conducted where plants were irrigated with three types of water; untreated wastewater, biologically treated wastewater and clean irrigation water (control). Results revealed that wastewater (biologically treated and untreated) fertigation led to soil basification as compared to control. Furthermore, pre- and post-harvest soil analysis revealed that initial nitrogen and phosphorus levels (N = 8 mg kg −1 , P = 5.2 mg kg −1 ) decreased after clean water irrigation (N = 0.9 mg kg −1 , P = 1.1 mg kg −1 ). Fertigation with biologically treated wastewater and untreated wastewater enhanced N and P where the former increased the levels moderately (N = 39 mg kg −1 , P = 47 mg kg −1 ) while the later to toxic ones (N = 61 mg kg −1 , P = 75 mg kg −1 ) as reflected from crop yield attributes. Application of untreated wastewater significantly decreased total soluble proteins, plant chlorophyll contents and the activities of carbonic anhydrase (CA), catalase (CAT) and aminocyclopropanecarboxylate oxidase (ACO) as compared with treated wastewater. However, biologically treated wastewater exerted no deleterious effects on the studied parameters, as compared with untreated wastewater and clean irrigation water, but significantly increased the plant biomass and yield. It is concluded that treatment of wastewater should be performed before its application to agricultural fields to maintain soil nutrient level and for sustainable crop productivity.