IMPORTANCE OF IMPROVING BIOLOGICAL ACTIVITY OF TEA SOILS IN SOUTHERN PROVINCE OF SRI LANKA.

Abstract

The detrimental effects of soil pesticides on soil micro biota and biodiversity of the teaecosystem are poorly understood. In the current study, microbial activity in southern teasoils of Sri Lanka as affected by application of commonly used soil pesticides and certaincultural practices was evaluated by m-:asuring the soil respiration in vitro and in vivo.

CO2 evolution rates in Southern tea soils were generally low as compared to soils in otherareas. Herbicide and formalin applications significantly (p=O.005) suppressed thebiological activity of Southern tea soils; the nematicide tested was less effective.Incorporation of compost and tea waste significantly (p=O.005) elevated CO2 evolution ratein tea soils than that of in undisturbed, virgin forest soils. Forking strengthened microbialbiomass through improved soil physical conditions. Soil biomass was positively correlatedwith growth of the test plants viz tea and tomato

Southern tea soils with low organic matter contents arc exposed to repeated application ofherbicides and negligence of important agronomic practices due to labour shortage. Suchmalpractices could aggravate potential build up of pesticide residues in the soil. Thus,improvement of soil organic matter status by incorporation of various organic amendments,establishment of green manure crops, rehabilitation of old tea soils and more importantly,restricted usage of agro-chemicals etc. is essential. These practices will assure long-termsustainable productivity and quality of soils as well as help degrade accumulated chemicalresidues and elevate densities of soil microbial communities. As a consequence, increasedefficacy of bio control of nematodes and soil borne pathogens and proper administration ofnatural nutrient cycles could be envisaged.