The application of irrigation water and nitrogen (N) fertilizer in excess of crop demand reduces profitability and has multiple detrimental impacts on the environment. N dynamics in agroecosystems are extremely complex, and mechanistic crop models are most often required to quantify the impact of improved management practices on reducing fertilizer N losses. In this study, Life Cycle Assessment (LCA) methodology and mechanistic modelling was used to quantify the environmental benefits of improved management of water and fertilizer N by sugarcane farmers in a case study in Pongola, South Africa. A baseline scenario, representing farmer intuition-based irrigation scheduling management, and two additional scenarios in which water, and water and N were more rationally managed, were compared. Results show that improved water and N management can lead to a 20% reduction in non-renewable energy consumption per functional unit (FU), with sustained or even increased yields. Total GHG emissions can potentially be reduced by 25% through more efficient water and N management.Limiting the rates of fertilizer N applied, made possible by decreasing N leaching through improved irrigation scheduling, resulted in the highest reductions for both impact categories.While total water consumption was very similar between the scenarios, more efficient use of † Bénéfices environnementaux de la gestion raisonnée de l'eau et de l'azote en canne à sucre irriguée :Approche combinée de modélisation de la culture et d'analyse du cycle de vie à Pongola, Afrique du Sud  Correspondence to: M. van der Laan,

Soil salinity is a well-researched issue. However, farmers' knowledge and perceptions of salinity management are less known. A questionnaire survey was conducted with 34 sugarcane growers, farming 18,174 ha under irrigation in South Africa. The questionnaire evaluated current knowledge levels, management practices, and perceptions about salinity management. The results reveal several knowledge gaps. Many farmers were not monitoring their soil salinity status or the water quality used for irrigation. A large portion (71%) of farmers observed visible signs of salinity; however, very few were implementing flushing of salts with irrigation. Contrastingly, participants suggested that they perceived the threat of salinity and have sufficient knowledge about causes and the preventative and corrective measures for salinity management. In addition, respondents were satisfied that the benefits of salinity management outweigh the costs. Participants, however, perceived practical difficulty and hassle factors relating to the knowledge and skill required for implementation. In conclusion, extension activities need to extend beyond knowledge sharing to the level of implementation. On-farm testing, demonstration plots, farm visits, and technical tours are recommended. Relevant economic and practical case study information must be gathered and shared with larger farmer groups.adoption, extension, knowledge exchange, soil salinity, sugarcane * Les niveaux de connaissance, les perceptions et les pratiques des agriculteurs irrigants dans le contexte de la gestion de la salinité du sol dans l'industrie sud-africaine de la canne à sucre.

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