Biomass Allocation and Productivity of Tree Seedlings in Responses to Soil Chemical Changes Under Treated Wastewater Irrigation in Indian Desert

Treated wastewater is an invaluable resource in meeting the growing demand of freshwater in tree crop irrigation in dry areas with additional benefits of land degradation reduction and biomass production. Seedlings of Acacia nilotica, Azadirachta indica, Eucalyptus camaldulensis, Prosopis cineraria, P. juliflora, Tamarix aphylla, Salvadora persica, S. oleoides and Tecomella undulata were planted and irrigated with bore-well (BW) and treated wastewater (WW) at ½ET (evapotranspiration) and ¾ET. Changes in soil properties and plant biomass allocation in different parts were assessed for species efficacy in phytoremediation of wastewater-contaminated soils and enhanced biomass yield. Irrigation enhanced soil pH, EC, SOC, available nutrients (greater in 0–30-cm soil layer than in 30–60-cm soil layer) and plant biomass. Wastewater irrigation had stronger effect in enhancing soil EC, SOC, NH4-N and NO3-N (3.50–76.92%), whereas increased quantity of irrigation showed stronger effects on PO4-P, K, and root and shoot biomass (7.63–51.20%). High biomass in A. nilotica, A. indica, E. camaldulensis and P. juliflora plants was supported by increased root biomass to exploit increased level of water and nutrients. Indigenous S. oleoides, T. undulata, P. cineraria and S. persica showed greater potential of salts and nutrient absorption from the wastewater-contaminated soils. Moderate increase in pH and EC with simultaneous increase in SOC, nutrients and biomass exhibited beneficial use of wastewater in dryland afforestation. A. nilotica, A. indica, E. camaldulensis and P. juliflora were most efficient in utilising treated wastewater and beneficially can be utilised in urban afforestation and sustainable development of dry areas.