Implications of organic management on yield,tuber quality and soil health in yams in the humid tropics

Global consciousness of food safety, health and environmental issues has stimulated interest in alternative agricultural systems like organic farming. Since information on organic farming of tuber crops is meagre, a field experiment was conducted in split plot design over a five-year period at Central Tuber Crops Research Institute, India. The aims were to evaluate the impact of organic, conventional and traditional production systems on yield, proximate composition and mineral content of tubers and soil physico-chemical and biological properties in three species of Dioscorea (white yam: D. rotundata, greater yam: D. alata and lesser yam: D. esculenta). The production systems were assigned to main plots and species to subplots. Organic farming (20.34 t ha-1) produced significantly higher yield over conventional practice (18.64 t ha-1) by 9%. All the species responded well to organic management, which lowered the bulk density and particle density slightly and improved the water holding capacity (by 15%) of soil. Tuber quality was improved with significantly higher Ca (72.67 mg 100g-1), slightly higher dry matter, crude protein, K and Mg contents. Organic plots showed significantly higher available K, by 34% and pH, by 0.46 unit and higher soil organic matter by 14%. The dehydrogenase enzyme activity (1.174 μg TPF formed g-1 soil h-1), population of bacteria, fungi and P solubilizers were promoted by 14%, 23%, 17% and 22% respectively. Thus organic farming was found to be an eco-friendly management strategy in yams for sustainable yield of quality tubers besides maintaining soil health. Technology involving farmyard manure, green manuring, neem cake, biofertilizers and ash was standardized. Keywords: Alternative farming; Dioscorea spp.; Productivity; Tuber quality; Soil quality.