Potential of meadowfoam (Limnanthes alba) seed meal as an organic source of nitrogen

Meadowfoam (Limnanthes alba Hartw. Ex Genth.), a member of the Brassicales order, is grown for its oil, which generates seed meal as a by-product. The potential of meadowfoam seed meal (MSM) for agronomic purposes is relatively unexplored, although MSM has shown promise for weed and pest control. Because of its high protein content, MSM may also be useful as an organic N fertilizer. The objective of this research was to characterize the dynamics of C and N released from MSM during its decomposition. The potential of MSM to produce plant-available N was evaluated in a laboratory incubation using rates similar to those applied in field studies of its weed control potential. Respiration (CO2 production rate), the activities of two enzymes involved in the degradation of MSM (β1,4-glucosidase and leucine aminopeptidase), and inorganic N (NH4+ and NO3−) were measured during a 56-d period. Respiration peaked during the first week, indicating rapid MSM decomposition, which was coincident with maximum potential activity of leucine aminopeptidase. Inorganic N (dominantly NH4+) peaked later, at two weeks, when about half of the N in the added MSM had been mineralized. Nitrification was delayed until six weeks, presumably because of inhibitory effects of the MSM, a phenomenon observed with seed meals of other brassicaceous plants. These results demonstrate the potential use of MSM as a slow-release, organic N amendment in crop production systems.