Changes in the physico-chemical and biological quality attributes of soil following amendment with untreated coffee processing wastewater

Discharge of untreated coffee processing wastewater (CPW) into natural water bodies without adequate treatment poses serious threat to environment. In India, due to high cost incurred in construction of ‘Effluent Treatment Plants’, coffee growers are employing rudimentary land based wastewater storage and treatment facilities at on-farm levels, which affects the soil quality. In the present study, we investigated the effects of untreated CPW at different loading rates (250 m3, 500 m3, 750 m3, and 1000 m3 per hectare) on soil physico-chemical and biological properties. Higher loading rates of CPW (75–100 L/m2) were found to significantly increase (p < 0.01) the electrical conductivity (EC), bulk density (BD), water holding capacity (WHC), organic carbon (OC), available nitrogen, available potassium, while the soil pH and available phosphorus were significantly reduced (p < 0.01) by higher loading rates. Application of higher volumes of CPW (75–100 L/m2) significantly reduced the soil respiration, dehydrogenase (DHA), urease activity and Fluorescin diacetate activity (FDA) at both the soil depths (0–15 and 15–30 cm). Significant decrease in populations of pelops, eulohmannia and springtail was observed with the application of higher volumes of CPW (75–100 L/m2). CPW at a rate of 25–50 L/m2 found to significantly increase the population of culturable bacteria (p < 0.01), fungi (p < 0.05) yeast (p < 0.01) and actinomycetes (p < 0.01), while their populations were drastically reduced above 75 L/m2. In functional microflora, application of CPW at a rate of 25–50 L/m2 found to significantly increase the population of Pseudomonas fluorescence (p < 0.01), phosphorus solubilisers (p < 0.05), Azotobacter sp. (p < 0.01) and Beijerinkia sp. (p < 0.05) at 0–15 cm.

► The present study evaluated the risk of storing untreated coffee processing wastewater at on-farm level on soil properties.
► The changes in soil properties were depend on the quantum of CPW stored.
► Storing of CPW at lesser volume (250 m3/ha) increased soil nutrients and other soil biological properties.