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Effects of water and nitrogen availability on nitrogen contribution by the legume, Lupinus argenteus Pursh

Goergen, Erin, Chambers, Jeanne C., Blank, Robert
Applied soil ecology 2009 v.42 no.3 pp. 200
Lupinus argenteus, forage legumes, nitrogen, nutrient availability, nitrogen fixation, soil water content, nodulation, plant growth, dry matter accumulation, nitrogen content, root growth, biogeochemical cycles, carbon nitrogen ratio
Nitrogen-fixing species contribute to ecosystem nitrogen budgets, but background resource levels influence nodulation, fixation, and plant growth. We conducted a greenhouse experiment to examine the separate and interacting effects of water and N availability on biomass production, tissue N concentration, nodulation, nodule activity, and rhizodeposition of Lupinus argenteus (Pursh), a legume native to sagebrush steppe. Plants were grown in a replicated, randomized design with three levels of water and four levels of N. Additional water and N increased biomass except at the highest N level. All plants formed nodules regardless of treatment, but plants grown without N had the largest, most active nodules. Organic N was deposited into the rhizosphere of all plants, regardless of treatment, indicating that Lupinus can influence N availability while actively growing, even under water stress. High tissue N concentrations and low C:N ratios indicate that Lupinus also can provide substantial amounts of N through litter decomposition. The ability of Lupinus to affect N availability and cycling indicates that it has the potential to significantly influence N budgets and community composition within the sagebrush steppe.