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Indian soils are inherently poor in quality due to the warm climate and erosion. Conversion of land uses like forests to croplands and faulty management practices in croplands further cause soil degradation. This study aimed to understand the extent of these impacts in a small representative part of eastern India, covering Himalayan terai and nearing alluvial plains. Soils were collected from (i) forests, (ii) croplands (under agricultural practices for more than 50–60 years) and (iii) converted lands (converted from forests to croplands or tea gardens over the past 15–20 years). Different soil quality indicators were assessed and soil quality index (SQI) was generated to integrate, scale and allot a single value per soil. Results indicated that continuous organic matter deposition and no disturbances consequence the highest presence of soil carbon pools, greater aggregation and maximum microbial dynamics in forest soils whereas high application of straight fertilizers caused the highest available nitrogen and phosphorus in cropland soils. The SQI scorebook indicated the best soil quality under forests (x¯ 0.532), followed by soils of converted land (x¯ 0.432) and cropland (x¯ 0.301). Comparison of the SQI spatial distribution with land use and land cover confirmed the outcome. Possibly practices like excessive tillage, high cropping intensity, no legume in crop rotations, cultivation of heavy feeder crops caused degraded soil quality in croplands. This study presented an example of soil quality degradation in India due to land use change and faulty management practices. Such soil degradation on a larger scale may affect future food security.

The work deals with the biochemical characterization of rhizospheric isolates including Indole, Methyl Red, Voges Proskauer, Citrate test (IMViC test) based quantitative biochemical assay, PGPR properties like nitrogen assimilation (in microbes), phosphate solubilization etc. A special aspect of finding the correlation between the biochemical tests and PGPR properties were also studied. Methyl red test and tryptophanase assay (by indole test) were found to be positively and negatively correlated with phosphate solubilization. Vogues Proskeur and citrate utilization tests were negatively correlated with the phosphate solubilization. In future, these biochemical tests can be used as determining factors to identify phosphate solubilizing bacteria. Moreover, a group of bacteria was identified by the scatter plot analysis which shows low acid production with high phosphate solubilization. Lastly, we have given a new approach of screening rhizospheric bacteria based on motility on nitrogen deficient media.