Cellulose Decomposition Potential of Soil as Affected by Vegetable Cultivation: A Case Study in Kegalle District, Sri Lanka

Abstract

The potential of microbial communities for organic C decomposition is a crucial factor determining CO2 emissions from soil, C storage, and short-term nutrient turnover. We conducted a study to assess cellulose decomposition potential (CDP) of soils as affected by vegetable cultivation. Ten sites cultivated with vegetables and five sites under natural vegetation, distributed in Atulugama and Kanangama Grama Nilaldhari divisions in Kegalle District of Sri Lanka, were selected for the study. The cultivated lands have been managed with organic fertilizers (n=4), synthetic fertilizers (n=3), or a combination of both types of fertilizers (n=3). Soils collected at 0-15 cm depth were used in a laboratory incubation experiment to assess CDP in triplicates for two weeks. The in situ CDP was studied by placing litter bags containing two types of cellulose materials, i.e. cotton wool or cellulose filter papers, separately for four and six weeks, respectively. They were placed at 5 cm depth in the field in two replicates. Vegetable cultivation had significantly (p<0.05) reduced soil organic C content. There was no significant correlation (p>0.05) between CDP observed under laboratory and field conditions. The effect of land management on CDP was significant (p<0.05) only in laboratory incubation, in which soils collected from the lands cultivated with synthetic fertilizers alone had nine-fold high CDP compared to uncultivated soils. In situ decomposition of added cellulose filter papers and cotton wool after four weeks ranged from 13-100% and 61-65%, respectively. Nearly 44% of sites exhibited values >80% for CDP. In conclusion, vegetable cultivation affected CDP differently depending on the nature of cellulose input and the history of fertilizer management.