Rationale of International Land Evaluation Methods under Aberrant Climatic Conditions in Shrink-swell Soils of Indian Semi Arid Tropics

A host of parametric land evaluation techniques like Land Capability Index (LCI), Storie index, Requier's method and Sys parametric method are in use for land evaluation under tropical environments. But these methods need assessment/refinement for applicability under aberrant rainfall condition which has been witnessed in central peninsular India in the recent times. In the present study an attempt has been made to assess the suitability of these methods in shrink-swell soils in dry sub-humid agro-ecosystem under varying rainfall regime through the analysis of farmers’ field data. Analysis of soil and crop yield data for five years reveals that Sys method bears reasonably good correlation (R²=0.7497) with cotton yield. However, in dry year, the index is low, whereas in wet and normal years it is reasonable. The most notable observation is that in spite of reduction in land index in dry year the soil suitability class remains unchanged, indicating the non-universality of the method. But reclassifying the index class, high correlation with cotton yield (R² = 0.972) is obtained. The index class has been revised with index more than 50 highly suitable, 50–30 moderately suitable, 30–20 marginally suitable and less than 20 not suitable for cotton to accommodate the rainfall variability. Therefore, the proposed index class is more appropriate and may be used for cotton suitability evaluation in shrink-swell soils of central India under varying rainfall regimes.