Constraints to Improving Nitrogen Fixation in Chickpea in the Central Dry Zone of Myanmar.

Myanmar (Burma) is one of the poorest countries in the world. Around 70% of Myanmar’s population is based in rural areas and are engaged in crop and livestock farming activities as a key source of income. Myanmar is the world’s second largest exporter of pulses, i.e., food legumes, after Canada. Myanmar farmers grow green gram, black gram pigeon pea, groundnut, chickpea and other legumes across an area of 4.4 million hectares, in rotation with rice, sesame, maize and other crops. Export markets are principally to India, with expanding markets in Vietnam and China. Pulses are widely grown in Myanmar’s CDZ by small-holder farmers, typically with minimal inputs. Despite the importance of legumes in Myanmar, there is little knowledge of the extent to which soil rhizobial populations contribute to N₂ fixation by crop legumes. Chickpea rhizobial populations were estimated in 20 soils in the Central Dry Zone of Myanmar and seven field experiments were established to determine whether the combined inputs of phosphorus (P) fertiliser and rhizobial inoculation improved chickpea nodulation, nitrogen fixation and grain yields. Chickpea rhizobial populations in 17 of the 20 sampled soils were less than 1000 rhizobia / g soil, indicating potential for increasing N₂ fixation through inoculation. Inputs of P fertiliser increased nodulation at two sites and increased grain yield at four sites. Rhizobial inoculation increased nodulation at one site and increased grain yield at three sites. There were no interactions between phosphorus and rhizobial inoculation for either nodulation or grain yield. Nitrogen fixation contributed, on average, 82% of chickpea nitrogen but did not differ among treatments. Despite significant responses, the impacts of P fertiliser and rhizobial inoculants were moderate and were likely to have been constrained by effective agronomic management, particularly nutrient deficiencies and crop protection. Further work to explore these issues is planned.