EFFECT OF BIOGAS SLURRY ON COMPOSTING PROCESS AND QUALITY OF CATTLE MANURE-BASED COMPOST AND VERMICOMPOST

Regarding the increasing demand of good organic manure, we made an attempt to generate a modified vermicompost from biogas slurry amended cattle manure. For this, six trials including control were run in pots by adding 2−10% (w/w, fw.) biogas slurry to cattle manure for 21 days for composting and 60 days for vermicomposting using E. eugeniae earthworms (10 per 500 g) under aerobic condition keeping moisture level of 70±5% within the overall temperature range of 13−39°C. The use of bacterial inoculants increased the agricultural quality of the compost and accelerated the composting process. After being maturity, pH of the vermicompost reached to 7.66, indicating that it has excellent nutrient releasing capability. Since EC of the produced vermicompost is less than 1.60 dS m−1, it has high cation-exchange capacity, which is beneficial to soil texture and plant health. An increment in 163% of available P in the vermicompost (6.35 ± 0.78 mg g-1, dw) than that in the compost and the highest increment of 264% with respect to control indicated that it was a better organic fertilizer and hence might be an alternative to P2O5. The worm-processed material for trials T1-T5 showed 10.0–32.5% more exchangeable K than control (T0). An increment of 43.84% in total N and an decrease of 15.6% in total organic C makes the vermicompost ideal for use for its lowest C:N ratio of 15:1, whereas it was 35:1 in compost. Each of the N-P-K contents was elevated significantly that made it a potential organic fertilizer. Comparison of the key parameters with vermicomposts of buffalo, pig, goat, horse, chicken and sheep manures of different countries confirms that the produced vermicompost could serve as an excellent organic manure.