Long‐term effects of various crop rotations for managing salt‐affected soils through a field scale decision support system – a case study

Abstract Appropriate crop rotations coupled to water use plans are the basic means of managing salt‐affected soils. Recommendation of suitable crop rotations for salt‐affected land requires prediction of their long‐term impact on soil salinity/sodicity build‐up and consequent crop yield reduction. This is conventionally achieved through long‐term field experiments. However, such evaluations are site specific, expensive and time consuming. Appropriate decision support systems (DSS) can be a cost‐effective means in such cases. This study demonstrates the application of one such DSS for recommending the best crop rotation for a salt‐affected field in Gurgaon district of Haryana (India). Before application, the DSS was extensively validated on 11 farmer's fields and one experimental field in Gurgaon and Karnal districts of Haryana. The DSS gave realistic estimates of root zone soil salinity/sodicity and relative crop yield reductions under the local management practices. These estimates were associated with absolute mean relative errors ranging between 0.02 and 0.24. Ten‐year impact assessments of existing (i.e. paddy–wheat, P‐W) and 10 alternative crop rotation plans with the validated DSS showed that pearl millet‐based sequences were, environmentally and agronomically, the most suitable options for the test field. However, a cost–benefit analysis of DSS‐simulated average annual crop yields, under various crop rotations, showed that the economic return of pearl millet‐based sequences was about 13% less than fallow–wheat (F‐W) rotations and 4% less than P‐W rotations. Hence F‐W was recommended as the most beneficial environmental choice and economically the most robust alternative crop sequence for the salt‐affected field.