PhD Oral Defense: Soil nitrogen dynamics following green manure plow-down determined by ion exchange membranes and the nitrogen uptake of arugula (Eruca sativa L.)

PhD Oral Defense of Leonardo Xavier León Castro, Natural Resource Sciences.

Green manure crop mixtures contain legumes that capture N2 from the atmosphere. When green manure is plowed down, the decomposing residues are a source of N fertilizer for the following crop. The challenge is to determine how quickly the green manure releases N and what proportion of the N requirements of the next crop can be met by green manure. Ion exchange membranes (IEMs) hold promise in evaluating the N supplied by green manure, and they act as a sink for plant-available N. The objectives of my thesis were to 1) determine the pattern of N release from field pea-oat green manure under field conditions with IEMs, and relate this to the N demands of arugula (Eruca sativa L.); 2) to determine if IEMs could detect small changes in N dynamics in different soil types that were amended with green manure residues having a low C/N ratio; and 3) to determine how tillage practices that reduce the size of green manure residues may accelerate N release from green manure, as determined by IEMs, and  meet crop N requirements.  

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