IS ORGANIC TUBER PRODUCTION PROMISING? FOCUS ON IMPLICATIONS, TECHNOLOGIES AND LEARNING SYSTEM DEVELOPMENT

Summary

Alternative soil management practices like organic farming assume special significance in the context of global warming and climate change for sustainable and safe food production. Organic farming enables a clean environment by promoting soil quality and sequestering soil organic carbon. Cassava, yams (white yam, greater yam and lesser yam) and edible aroids (elephant foot yam, taro and tannia) are tuberous vegetables with good taste and nutritive value. Seven field experiments were conducted in series at the Central Tuber Crops Research Institute, Thiruvananthapuram, India, over a decade (2004-2013) to compare the varietal response, yield, quality and soil properties under organic farming over conventional system in these crops and to develop a learning system based on the data generated. The industrial as well as domestic varieties of cassava, the elite and local varieties of elephant foot yam and taro and the three species of Dioscorea (yams) were on a par under both systems. However, the industrial variety of cassava yielded more under organic farming than conventional practice. The yield trend over the years as well as pooled analysis indicated the significantly superior performance of organic farming in elephant foot yam. Organic farming produced slightly higher yield in cassava and trailing genotypes of yams. This indicates that elephant foot yam was the most responsive to organic management followed by yams and cassava. Taro and dwarf white yam preferred chemical farming as slight yield reduction (2-5%) was noticed under organic farming with almost similar tuber quality. Thus organic management promoted yield by 8%, 20%, 9%, 11% and 7% over conventional practice in cassava, elephant foot yam, white yam, greater yam and lesser yam respectively. The tuber quality was improved with higher dry matter, starch, crude protein, K, Ca and Mg contents. The anti-nutritional factors, oxalate content in elephant foot yam and cyanogenic glucoside content in cassava were lowered by 21 and 12.4% respectively. Organic plots had significantly higher water holding capacity, pH, available K, Fe, Mn and Cu, higher soil organic matter, available N, P, exchangeable Ca and Mg, dehydrogenase enzyme activity and microbial count. Cost-benefit analysis in elephant foot yam indicated that the net profit was 28% higher and additional income of Rs. 47,716 ha-1 was obtained due to organic farming. The on station technology developed for elephant foot yam was validated and popularized through on farm trials in 10 sites (5 ha) under National Horticulture Mission funded programme. The technology is included in the Package of Practices Recommendations for crops of Kerala Agricultural University. A learning system was developed using artificial neural networks (ANN) to predict the performance of elephant foot yam organic production system. Use of organically produced seed materials, seed treatment in cow-dung, neem cake, bio-inoculant slurry, farmyard manure incubated with bio-inoculants, green manuring, use of neem cake, bio-fertilizers and ash formed the strategies for organic production. Organic farming is an eco-friendly management strategy that enables 10-20% higher yield, quality tubers and maintenance of soil health in tuber crops.