09-08-2013, 03:27 PM
Effect of soil solarization and ammendments on microbial population and physical properties of soil in relation to soil borne diseases.
ABSTRACT
Soil organisms are creatures that spend all or part of their lives in the soil environment. Every handful of soil is likely to contain billions of organisms with representatives of nearly every phylum of living organisms. Soil-borne diseases result from a reduction of biodiversity of soil organisms. Restoring beneficial organisms that attack, repel, or otherwise antagonize disease-causing pathogens render a soil disease-suppressive. Plants growing in such suppressive soil resist diseases much better than in soils low in biological diversity. Soil borne diseases are the major constraints in the successful cultivation of crop and a number of pathogens have been found to be associated with such diseases, of which Fusarium oxysporum, Rhizoctonia solani and Pythium aphanidermatum (fungi), Ralstonia solanacearum (bacterium) and Meloidogyne incognita (root knot nematode) are the most common (Doolittle, 1953; Das and Chattopadhyay, 1955; Darekar and Mhase, 1988). Managing the soil borne diseases though quite difficult, however, various measures have been adopted to manage them with the aim to either eliminate or reduce the primary inoculum in soil in or on the seed or propagating material. Soil solarization is a simple nonchemical technique that captures radiant heat energy from the sun. This energy causes physical, chemical, and biological changes in the soil. These changes lead to control or suppression of soil borne plant pathogens such as fungi, bacteria, nematodes, and pests along with weed seed and seedlings. Soil solarization, a hydrothermal process, was studied for assessment of its effect on physical (temperature, pH and moisture) properties of soil. Soil solarization integrated with different amendments and bioagents increases the efficacy of soil solarization and prolonged effectiveness of soil solarization. Soil solarization with transparent low density polyethylene mulch (25 µm) increased soil temperature by 10-12ºC at 5, 10 and 15 cm depths as compared to non-solarized plots. Maximum increase in temperature was observed at 5 cm depth. Polyethylene mulching facilitated higher soil moisture conservation. The rise in soil temperature resulted in decrease of fungal, bacterial and nematode population, whereas, there was increase in the actinomycetes population. Integration of soil solarization + seed treatment with Mancozeb + Metalaxyl was found most efficacious in reducing the damping off over control, however it was at par with soil solarization + seed treatment with isolate Tv4 (Trichoderma viride) under in vivo conditions.