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.