06-08-2013, 04:55 PM
Root disease management in organic faming systems
ABSTRACT
Conventional farming practices with time have led to decline in soil structure, fertility and microbial diversity and simultaneously given rise to many diseases, soil and root borne diseases. The escalating cost of chemical fungicides, threat of pollution to soil, water, air and development of pathogenic resistance to these chemicals have diverted the attention of scientists. Root diseases are more damaging when soil conditions are poor as a result of inadequate drainage, poor soil structure, low organic matter and low soil fertility. In organic farming systems, famers apply many cultural measures like cultivar choice, promotion of soil health by organic amendments, low tillage and natural habitat diversification. Pathogen suppression under organic farming is dependent upon quality of the residues and the stage of their decomposition and their disease suppressive properties rely on number of factors including microbial activity, microbial population dynamics, nutrient concentrations and other associated chemical and physical factors. Organic amendments coupled with no pesticide use enhance both microbial diversity and biochemical activities in soil which decrease disease inoculum through competition and antibiosis mechanisms and increases defence mechanism by antioxidant production. In organic system plants roots get better colonized by mycorrhizal fungi which protect them from root invading pathogens. Organic farmers also use biological control agents and natural toxic compounds of plant extracts however, these are methods of last resort.