See more from this Session: Microbe, Plant , and Soil Interactions (Includes Graduate Student Poster Competition)
Monday, October 17, 2011
Henry Gonzalez Convention Center, Hall C, Street Level
Northern Great Plains agroecosystems have benefited from the inclusion of pulse crops into traditional cereal-based crop rotations. In particular, pulse crops can improve the N nutrition of subsequent crops through N sparing and decomposition of N-rich residues from biological fixation of N2 by the Rhizobium-legume symbiosis. Field pea meets ~60% of its N requirement through fixation, a large portion of which is lost from the system when the N-rich grain is harvested. A net input of fixed-N to soil will only occur when the amount of fixed-N remaining in the residues exceeds the amount of soil-derived N that is removed in the grain. However, quantifying the remaining N in crop residues requires an adequate accounting of belowground contributions, including N released from living pulse crop roots as rhizodeposits. This study aims to directly quantify root and rhizodeposit N from field pea at vegetative, flowering, and physiological maturity in a controlled environment experiment through continuous labelling of the soil atmosphere with 15N2. In total, 24 pea plants, each grown in separate pots are supplied with a soil atmosphere enriched to 5.0 atom % 15N excess. The soil and roots are contained within this enriched atmosphere, while the aerial parts of the plant are exposed to ambient atmospheric conditions. The stem of the plant is fed through a hole in the cap of the pot and the hole is sealed with silicone and paraffin wax to avoid gaseous loss. The 15N2 enriched soil atmosphere is continuously circulated through each individual pot at constant flow rate of 200 mL min-1. Oxygen and CO2 concentrations as a result of respiration activity are monitored and adjusted as needed. Preliminary results highlighting the quantity of fixed-N released from field pea as rhizodeposits at vegetative and flowering growth stages will be presented.