Evaluation of Decomposition Rates and Suitability of Various Crop Residues for Vermicompost Production

Aims: Evaluation of decomposition rates and suitability of various crop residues for vermicompost production. Study Design: Randomized block design (RBD) . Place and Duration of Study: Centre for Organic Agriculture Research and Training Farm, Department of Agronomy, Dr. PDKV, Akola during experimental period of October 2018 to February 2019. Methodology: The experiment was laid out in randomized block design with eight treatments and replicated thrice. The treatments comprised various crop residues: soybean straw, rice straw, wheat straw, sunhemp stalk, foxtail millet straw, pigeonpea stalk, cotton stalk, and a mixture of available grasses and crop residues. Eisenia foetida earthworm species was utilized for the study. Results: The present study was formulated to evaluate decomposition rate and suitability of various crop residues for vermicompost production. To examine these parameters such as periodical changes in mean temperature, change in weight and recovery ratio, time taken for maturity, moisture content (%) at maturity and periodical changes in C: N ratio of crop residue during vermicomposting preparation are studied. The result showed that, as vermicompost preparation proceeded, the temperature was steadily decreased towards maturity in all crop residue used as substrate for vermicompost production. The maximum final weight (11.0 kg), higher percentage of vermicompost yield recovery (55.0%) was achieved in soybean straw (T1) substrate followed by sunhemp straw (T4), which has final weight (10.5 Kg) and yield recovery of vermicompost (51.2%) respectively. The highest reduction in the final volume of vermicompost was observed in rice straw (T2) (0.036 m3) being at par with soybean straw (T1) (0.039 m3), sunhemp stalk (T4) (0.043 m3) and wheat straw (T3) (0.044 m3) and minimum reduction in final volume was recorded with pigeonpea stalk (T6) (0.069 m3). Vermicompost maturity was significantly earlier in soybean straw (T1) (65 DAF) followed by foxtail millet straw (T5) (68 DAF) and traditional heap method (T8) (72 DAF). At maturity, the lowest C:N ratio (%) exhibited in vermicompost derived from soybean straw (T1) (17.24%), followed by vermicompost from sunhemp stalk (T4) (18.09%) and the traditional heap method (T8) (18.41%). Conclusions: Soybean straw proved to be the most suitable substrate for producing high-quality vermicompost, followed by sunhemp and pigeonpea stalk after assessing different parameters. Among parameters especially, the C:N ratio of crop residue at maturity is low, which positively affected the composting duration and quality of vermicompost.