Response of Diverse Legume Species to Ingenious Nitrogen-Fixing Bacteria on Delmarva Peninsula.

Legume crops have the ability to fix atmospheric nitrogen through a symbiotic relationship with rhizobia and bradyrhizobia. This association improves soil fertility, sustainability, and reduces contamination of soil and water bodies by chemical fertilizers amendments. This study was conducted, in 2014, and was repeated in 2105 and 2016 growing seasons, to identify high performance genotypes of soybeans (Glycine max), pigeon peas (Cajanus cajan), and mung beans (Vigna radiata), examine their adaptability to the Delmarva environmental conditions, and to study their response to ingenious nitrogen-fixing bacteria. Soybeans have been grown on the Delmarva Peninsula for centuries and are well-established, with the soils harboring mainly soybean bradyrhizobia. Pigeon pea and mung bean were included in this study because of their tolerance to elevated temperature and drought, which the Delmarva Peninsula is prone to during the growing season. Four genotypes of each of soybean, pigeon pea, and mung beans were grown in replicated field plots (n=4) in a randomized complete block design at the UMES Agricultural Experiment Station. When 50% of the plants were at flowering stage, 5 plants from each replicate were randomly selected from the middle row and dug up carefully. Nodule numbers, nodule dry weight, nodule efficiency, shoot and root dry weight, per plant, as well as seed yield were determined. Our results indicate that seed yield, nodule numbers, and nodule efficiency varied among legume species and also among varieties. Average nodule numbers per plant were 39.1, 9.4, and 4.8 for soybean, mung bean, pigeon pea, respectively. Nodule efficiency were 89.4, 31.0, and 46.1% for these plant species, respectively. The high efficiency of soybean nodules is due to its well-establishment on the Delmarva Peninsula. The pigeon peas and mung beans were able to nodulate with native rhizobia and bradyrhizobia, but not at the same rate as the soybeans. More studies are needed to insure the maximum adaptability of mung beans and pigeon peas to the Delmarva environmental conditions.