TEMPERATURE RESPONSES OF BIOMASS–MANURE MIXTURES DURING VERMICOMPOSTING: TREATMENT AND SEASONAL COMPARISONS

Abstract

Temperature is a practical process indicator in vermicomposting because it reflects the balance between microbial heat generation and heat loss and influences earthworm activity. This study described weekly substrate temperature in seven biomass–animal dung mixtures during two 12-week vermicomposting batches at Jorhat, Assam, India, in 2022 (Season I, June–August; Season II, October–December). Biomass (Eichhornia crassipes, Ipomoea carnea and banana pseudostem, with rice stubble replacing 30% of the biomass in three treatments) and animal dung (cow dung, poultry litter or their mixtures) made up 60% and 40% of each mixture by weight, and Eisenia fetida was used. The experiment comprised seven substrate treatments, each maintained in three replicate tanks (21 tanks in total). Substrate temperature was recorded separately in each replicate tank twice daily, and treatment-wise mean temperatures were calculated. The overall mean temperature was 28.14°C in Season I and 25.78°C in Season II, a difference of 2.36°C. Treatment-averaged temperature peaked in week 5 in Season I (29.77°C) and in week 6 in Season II (27.47°C), then declined to 26.21°C and 22.74°C by week 12. Differences among treatments were small (≤0.62°C) but consistent: the 12-week mean increased with the poultry-litter share of the dung fraction, T4 (poultry litter only) exceeded T1 (cow dung only) in all 12 weeks of both seasons, and replacing 30% of the biomass with rice stubble changed the mean by no more than 0.08°C. Substrate temperature remained between 22.0 and 30.4°C, and the seasonal difference in substrate temperature was far smaller than the difference of about 6.8°C in ambient air temperature between the two periods. The recorded temperature range of 22.0–30.4°C roughly indicated a predominantly moderate-temperature processing environment, with no sustained high-temperature phase observed in either season. However, the mean temperature throughout the production cycle increased with the poultry-litter share of the dung fraction in both seasons.