Development and application of a decision support system for optimizing cropping patterns under saline agriculture conditions in Rechna Doab, Pakistan

Secondary salinization processes in arid climates can be managed with effective policy decisions through stakeholder engagement. In developing countries such as Pakistan, effective management solutions also need to consider limited resources such as small land holdings, the poor economic status of farmers, and limited modeling and mathematical skills. This paper is part of a research project conducted to address such challenges via the development of a comprehensive but simple decision support system using a participatory modeling approach. The paper discusses the process of optimizing management on temporal and spatial scales with the consideration of soil salt balance, water availability, and market values of crops. Two major components of the system are: (i) a system dynamics model that describes socio-economic factors such as market values; and ii) a physically based model that simulates the salt balance in the root zone with conjunctive use of canal and tube well irrigation water. The integrated dynamic model was calibrated (R2 = 0.90) and validated (R2 = 0.82) against observed data sets of groundwater depth. Three policy decisions were examined: 1) Base case 2) Bioremediation by growing salt tolerant fodder such as Sudan grass; and 3) Optimum land allocation with different favorable crops (i.e. maximize crop returns while minimizing yield reduction due to salt and water stress). Bioremediation techniques are shown to be helpful in reducing the salt balance of the crop root zone in the long term. Optimizing cropping patterns are found to be effective as a short term solution, but this keeps on increasing the salt balance due to conjunctive water application.