Co-composting of green leaves and kitchen waste: characterization of organic amendments, microbial activity and analysis of defence enzymes in plants

Co-composting of green leaves and kitchen waste at low initial carbon-nitrogen (C/N) ratios was carried out to improve the available nutrients. Composting was performed in a pile for a period of 42 days, and physico-chemical factors, including, moisture content, pH, electrical conductivity, total Kjeldahal nitrogen, total carbon, and germination index were investigated. The pH of the compost increased exponentially up to 21 days of treatment and it was found to be as its maximum at day 42 (7.69 +/- 0.09). EC was observed at 3.1 +/- 0.23 mS/cm after day 1 of treatment and it increased to 5.61 +/- 0.48 mS/cm after 14 days of composting. EC decreased after 28 days of the composting process and was stable after 35 days. After 7 days of composting process, organic matter was 74.3 +/- 2.8% and decreased as 54 +/- 3.1% within 21 days. The total organic carbon content was determined as 39.2 +/- 1.8% at day 1 and the stable organic carbon level was determined to be 24.1 +/- 0.9% after 42 days. The total Kjeldahl nitrogen content of the compost was determined as 1.1% before initiating the composting process. After the third and fourth weeks, the total Kjeldahl nitrogen increased gradually (1.7 +/- 0.2%) and it was 1.9 +/- 0.15% in the compost after 28 days. The C/N ratio decreased after 1 week (31) and decreased to 15.7 after 28 days of composting. The C/N ratio was 12.1 after 42 days of composting showing maturity. The microbial population was observed during the composting process, and it varied significantly (p < 0.05). In 1 and 2 weeks of compost, the germination index was 42.3 +/- 2.8% and 48.3 +/- 2.6%, respectively, and it improved to 100% after 42 days of mature compost indicating suitability in soil amendment (p < 0.05). The organic nutrients improved soil microbial activity in the greenhouse. The organic amendments improved the health of the whole plant and improved the yield of green gram (p < 0.05). The applied organic nutrients improved peroxidase, phenylalanine ammonia lyase, and polyphenol oxidase activity in Vigna radiata seeds (p < 0.05).