Development of a land quality index for sorghum in Indian semi-arid tropics (SAT)

The present study demonstrates the development of crop specific land quality index (LQI) for sorghum [sorghum bicolor (L.) Moench] under semiarid tropics of India. The method developed as LQI is a function of climatic quality index (CQI) and soil quality index (SQI). The CQI defined as growth index was derived from the compound product of water satisfaction index and radiation index. The SQI was developed as multiple attributes of soil properties related to sorghum suitable soil quality such as soil depth, available water capacity (AWC), drainage and slope. The LQI was correlated with the actual sorghum yield obtained from benchmarks soils and it was found that LQI bears good agreement with the yield. From the yield correlation, the LQI class has been fixed as LQI value < 1.0 rated as high, 1-1.5 as moderate and > 1.5 as low corresponding to the maximum attainable yield of > 50%, 40-50% and less than < 40%, respectively. The study also indicated that CQI value of < 0.25 and SQI value of < 5 correspond to good sorghum growing area. Finally, the isoline maps of CQI and SQI maps were superimposed through TYDAC-SPAN-GIS system to arrive at LQI class map. The map indicates that out of a total area under sorghum (11.7 m ha), 43% falls under high LQI class, and 38% under moderate, and 19% under low LQI class. The moderate and low LQI areas need proper rehabilitation measures for increasing sorghum yield. The LQI developed may help in planning and management of soils not only under Indian SAT but also in areas of similar soil and climatic conditions occurring elsewhere. (C) 2001 Elsevier Science Ltd. All rights reserved.