Determining soil quality indicators for alluvial plains in the semi-arid tropics

Evaluating soil quality in the alluvial plains of the semi-arid tropics is vital to understand the impact of existing land management practices, thus facilitating the adoption of more sustainable agricultural methods. We analysed soil profiles using 146 horizon-specific samples from 24 pedons, representing seven soil series from the sub-tropical to semi-arid River Cauvery Delta basin, Tamil Nadu, India. Using principal component analysis (PCA), we identified minimum datasets (MDS) from 30 different soil properties. The plough layer's MDS were clay content, exchangeable sodium percentage (ESP), very coarse sand content, soil pH and soil organic carbon (SOC). For the subsurface layer, sand content, ESP, SOC, diethylene-triamine-pentaacetic acid extractable zinc (DTPA-Zn), and very coarse sand content were identified as the MDS. Soil quality index (SQI) values were 0.47-0.72 for the plough layer and 0.46-0.56 for the subsurface soil, suggesting limited soil function support in subsurface soils. Surface soil-site suitability criteria displayed a moderate correlation with SQI values derived via PCA, with additive (R-2 = .545) and weighted additive indices (R-2 = .659). Both simple additive index and weighted derived SQIs demonstrated a moderate association with rice yield (R-2 = .50 and .55, respectively). This research indicates the potential to identify soil quality indicators in alluvial plains of semi-arid tropics.