Saturday, 15 July 2006

Seed priming with molybdenum alleviates molybdenum deficiency and poor nitrogen fixation of chickpea in acid soils of Bangladesh and India.

C. Johansen1, A.M. Musa1, J.V.D.K. Kumar Rao2, D. Harris3, A.K.M. Shahidullah1, and J. G. Lauren4. (1) Peoplesí Resource Oriented Voluntary Association (PROVA), B/220, Kazihata, G.P.O. Box 15, Rajshahi, Bangladesh, (2) International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Global Theme - Agroecosystems, Patancheru, India, (3) CAZS Natural Resources, University of Wales, Bangor, United Kingdom, (4) Cornell University, Dept. Crop and Soil Sciences, Ithaca, NY 14853

Molybdenum (Mo) is a major limiting nutrient for chickpea production (Cicer arietinum L.) on the acid surface soils of the High Barind Tract (HBT) Bangladesh and eastern India. Nitrogen fixation by chickpea on these soils is generally poor but seed-coat inoculation of Rhizobium has given inconsistent results. Initial experimental work showed that nodulation, plant growth and grain yield were improved with addition of Mo to the soil. Multilocational farmer field trials testing soil applications of 500 g Mo ha-1 had grain yield responses of 58-173% across the HBT as well as an additional slight, non-significant, response to Rhizobium inoculation. Despite these positive responses to soil applied Mo, compound fertilizers containing Mo are unavailable in Bangladesh, and it is impractical to evenly broadcast the small amount of Mo required (<500 g Mo ha-1). Studies in Nepal and at ICRISAT, India have indicated the feasibility of supplying sufficient Mo and Rhizobium to the seed by adding these in the seed priming water. Earlier work has shown that seed priming, soaking the seed in water for 8 hr overnight prior to sowing, substantially increased chickpea yield in the HBT. The effect of adding Mo alone or Mo with Rhizobium to priming water was compared with soil application of Mo in farmer fields during 2003-04. Although adding Mo alone to the priming water did not significantly improve yield over the control, there were significant responses of 37-90% across the HBT by adding both Mo and Rhizobium to the priming water, which was similar to that obtained when Mo was applied directly to the soil. Likewise at 48 trials in eastern India the mean yield increases over control without Mo ranged from 17% to 22% when Mo was applied through seed priming water and 20% to 25% when Mo was applied to the soil. Additional on farm evaluations in 2004-05 had mean responses to Mo + Rhizobium addition, compared to priming with water only, of 9 to 25%. Since Mo is an essential element for human nutrition as well as plants, we also determined the Mo content in chickpea grain produced from control, soil Mo and priming Mo treatments. Relative to the controls, Mo contents increased 1.2 to 8.9 fold in grain from the Mo + Rhizobium priming treatments and 1.3-17 fold in grain from the soil applied Mo treatments. Chickpea grain Mo contents tended to be higher in the treatments where Mo was applied to soil as compared to Mo in the priming water. Variability in the Mo content of chickpea grain appears to be due to soils, varietal differences or abiotic/biotic stresses (drought, Botrytis gray mold). Our results suggest that poor nitrogen fixation by chickpea, due to Mo deficiency in the HBT of Bangladesh and eastern India can be effectively alleviated by a simple low-cost seed priming technique which is within the scope of resource-poor farmers. In addition increased levels of Mo in chickpea grain produced by Mo additions to priming water can be helpful in improving human intakes of this essential element.

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