Cultivar effects on nitrogen fixation in peas and lentils
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- Abi-Ghanem, R., Carpenter-Boggs, L. & Smith, J.L. Biol Fertil Soils (2011) 47: 115. doi:10.1007/s00374-010-0492-6
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Increasing nitrogen fixation in legume crops could increase cropping productivity and reduce nitrogen fertilizer use. Studies have found that crop genotype, rhizobial strain, and occasionally genotype-specific interactions affect N fixation, but this knowledge has not yet been used to evaluate or breed for greater N fixation in US crops. In this study five USDA varieties of lentils (Lens culinaris Medik.) and five varieties of peas (Pisum sativum L.) were tested with 13 to 15 commercially available strains of Rhizobium leguminoserum bv. viciae to identify the better N fixing rhizobial strains, crop varieties, and specific pairings. Peas and lentils inoculated with individual strains were grown in growth chambers for 6 week. Plants received (15NH4)2 SO4 (5 at.%) starter fertilizer to measure N fixation by isotope dilution. Below- and above-ground biomass, numbers of nodules, and the proportion of plant N supplied by fixation (PNF) were determined. The percent of N fixed was significantly affected by crop variety and significantly correlated with number of nodules in both lentils and peas. This implies that one strategy for enhancing crop N fixation is developing varieties that have higher rhizobium infection rates. Total N fixation in lentils was significantly influenced by both crop variety and rhizobial strain. Eston variety lentil and Shawnee variety pea had the highest PNF of 80.8% and 91.3%, respectively. The different strains of R. leguminoserum affected PNF in lentils but not in peas. These findings suggest that N fixation improvement in lentils and peas may be addressed most effectively by breeding crops for greater N fixation hosting capacity.