Changes in Physico-Chemical Characteristics of Soil Following Application of Rice Mill Wastewater Under Pot Irrigation Conditions

A study was undertaken to investigate the physico-chemical characteristics of soil irrigated with rice mill wastewater during winter crop period under pot irrigation conditions. Prior to the pot experiment, the physicochemical characteristics of the rice mill wastewater were measured. The wastewater revealed an alkaline pH (8.0) with DO (0.9 mg/l), COD (630 mg/l), TDS (670 mg/l) and total suspended solids (530 mg/l) and BOD (450 mg/l). Moreover, the wastewater was rich in sodium (235 mg/l), total phenols (35/l) as well as silica (58 mg/l). Twenty cemented pots of 40 cm(b) × 40(l) × 80(h) cm were used for the pot experiment. Pots were filled with 10 kg of soil each, different concentrations (0, 25, 50, 75 and 100%) of rice mill wastewater were prepared in dilution with tap water and irrigated to the pots before plantation of rice saplings. For each concentration four replicates were taken. Twenty days old Jaya T 90 variety of rice saplings, which were planted in the field, was transferred to the pots with three saplings in each pot. The experiment was carried out during the month of winter (December–February) when prevailing atmospheric temperature was between 10–30 °C. After experiment was over (i.e., at the time of harvest after 105 days) four random soil samples from each pot were again collected for physicochemical analysis. The textural parameters like clay and silt were found to be increased remarkably in the experimental pots over control pots. The clay, silt and fine sand contents were increased from 10.66–34.66%, 15.97%–63.28% and 1.4–4.49% respectively and coarse sand content was decreased from 6.6–24.42% in 25–100% rice mill wastewater irrigated pots. Parameters like conductivity, OM, OC, C/N ratio, Na⁺, SO^2– ₄, PO^2– ₄, Cl^–, phenols, SAR, CEC, ESP and %Na showed significant increased in 25% to 100% effluent irrigated soil, whereas the parameters like Nitrogen, Ca⁺⁺, Mg⁺⁺ and K⁺ were decreased over the control plots.