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Waste water irrigation in the regulation of soil properties, growth determinants, and heavy metal accumulation in different Brassica species

Sahay, Seema, Iqbal, Saba, Inam, Akhtar, Gupta, Meetu, Inam, Arif
Environmental monitoring and assessment 2019 v.191 no.2 pp. 107
Brassica juncea, Brassica napus, Brassica nigra, Brassica rapa subsp. oleifera, NPK fertilizers, agricultural land, cadmium, chromium, cole crops, copper, freshwater, groundwater, heavy metals, irrigation scheduling, irrigation water, lead, leaves, monitoring, nickel, nitrogen, phosphorus, physicochemical properties, potassium, soil nutrients, soil properties, sowing, wastewater, wastewater irrigation
To evaluate the impact of waste water (WW) irrigation, four Brassica species, namely B. campestris, B. juncea, B. napus, and B. nigra, were grown for 2 years in the agricultural field. First-year experiment (2014–2015) was conducted with the comparative effect of WW and ground water (GW) under a uniform dose of NPK (N₈₀P₄₅K₄₅, kg ha⁻¹). WW irrigation proved efficacious over GW to increase growth, physiological, and yield parameters. Increase in all parameters was due to the use of WW which leads to the improvement in the physico-chemical properties of soil as compared to resulted soil from GW application. Second-year experiment (2015–2016) therefore deals with WW irrigation only but under interaction with two levels of NPK fertilizers (N₈₀P₄₅K₄₅ and N₆₀P₃₀K₃₀, kg ha⁻¹). Results of this year revealed that maximum enhancement in growth, physiological, and yield parameters was observed at WW × N₆₀P₃₀K₃₀ and the input of WW × N₈₀P₄₅K₄₅ was not of benefit. WW × N₆₀P₃₀K₃₀ treatment was beneficial also because, at this treatment level, the accumulation of Cr, Cu, Pb, Ni, and Cd in leaf and seed was comparatively lesser in amount than that of WW × N₈₀P₄₅K₄₅. The study concluded even though the use of WW was applicable to save freshwater, enhance soil nutrient status, and make N, P, and K balance at their lower inputs, WW irrigation caused accumulation of heavy metals in all Brassica crops far above the safe limits during a quite longer irrigation time (70 days and 105 days after sowing (DAS)). However, WW was safe to use only up to 35 DAS. Therefore, the study suggested that there should be regular monitoring of heavy metal concentrations in irrigation water as well as in various crop vegetables.