NLOS-OG: a management tool for nitrogen fertilization in organic greenhouses

P.P. Dion, M. Thériault, D. Hunt, S. Bittman, S. Pepin, M. Dorais
Because of the complexity of the nitrogen (N) cycle and the diversity of its molecule forms in the soil, N fertilization management is based on complex conceptual or computational models. For organic farming, N is provided via organic amendments and biological fixation. However, lack of precise tools that predict the N mineralization rate of N sources lead some producers to over-fertilize, resulting in the buildup of salinity, N leaching and possible loss of profits. Consequently, better knowledge of N availability following organic fertilization, to improve synchronization of N supply with crop N demand, is crucial to advance sustainable organic horticulture. Our objective was to determine the mineralization rate of commonly-used organic N fertilizers by adapting a broad N management tool to guide N fertilization in organic greenhouse. We conducted a one-year incubation experiment to determine whether N mineralization of a mix of organic fertilizers can be predicted from mineralization rates determined individually for each fertilizer, and if the prediction is accurate across N application rates. We adapted the existing N management model NLOS ( to greenhouse organic horticulture and employed data from the incubation experiment to model organic fertilizers with low C/N ratio. We also report a N budget from an organic tomato greenhouse crop as validation of the model. In its current state, our model slightly underestimates mineral N in organic greenhouses, while allowing good and easily obtained estimates of N availability and losses. A web-based interface for the model (NLOS-OG) will soon be freely available. This new tool will help growers manage N by improving the synchronization of supply of organic fertilization with crop demand. The NLOS-OG tool is available at
Dion, P.P., Thériault, M., Hunt, D., Bittman, S., Pepin, S. and Dorais, M. (2020). NLOS-OG: a management tool for nitrogen fertilization in organic greenhouses. Acta Hortic. 1296, 1093-1098
DOI: 10.17660/ActaHortic.2020.1296.138
amendment, leaching, mineralization, STELLA model, nitrogen cycle, organic fertilizer, uptake

Acta Horticulturae