Analysing farming practices to develop a numerical, operational model of farmers’ decision‐making processes: An irrigated hay cropping system in France

Conventional water management in the Crau plain needs to be modified to ensure higher irrigation efficiency, better crop production and quality, and reduced environmental impacts. Because experimental approaches to test modifications of water management are difficult in relation to border irrigation, simulation may provide an alternative. We describe the development of a conceptual model of the decision‐making process that determines the irrigation management of a cropping system, on which a simulation model is to be based. Interviews focused on water management were carried out, to understand how farmers manage their irrigation and how their decisions determine the technical system applied on the farm. These interviews were then analyzed using the ‘model for action’ concept, to generate a conceptual model of the decision system, which is organized as a sequence of decision rules describing irrigation management. This model contains five elements: (1) spatial and temporal factors relevant to decision‐making in terms of irrigation and hay cropping; (2) no interaction between the grassland cropping system and the sheep rearing system; (3) five rules to describe irrigation management in the cropping system; (4) major water distribution constraints; and (5) two inter‐related operations, hay mowing and irrigation. The rules for irrigation decision‐making are written as: ‘If <Indicator> <Operator> <Threshold> Then <Action1> Else <Action2>’. This conceptual model was used as the basis of a decision support system that includes models of grass growth and hydrology.