Physio-chemical characterization of cumin and coriander growing soils of semi-arid zones of India and its bioprospecting for plant growth promoting rhizobacteria

Cumin and coriander are indeed vital spices in Indian cuisine and are predominantly cultivated in the arid zones of India like- Rajasthan and Gujarat. The quality and yield of any crop are strongly influenced by soil characteristics and the environmental conditions of the geographical region. In this study, a field survey was carried out for numerous locations of cumin and coriander growing areas to understand the physicochemical and microbial properties of cumin and coriander growing soils of Rajasthan and Gujarat. A total of 31 soil samples were collected and analysed for electric conductivity (EC), pH, organic carbon (OC), nitrogen (N), phosphorus (P), potassium (K) and total microbial counts. A considerable variation was found in soil pH levels of different soil samples which ranged from pH 6.80 to pH 9.03. The EC was found in the range of 0.56 to 0.99 ms/cm. The organic carbon, available nitrogen, phosphorus and potassium were found respectively in the range of 0.29 to 0.92 %, 135-382.8 kg/ ha, 6.16-18.25 kg/ha and 261.0 kg/ha to 412.5 kg/ha. Bacteria were isolated from these soils and based on morphological differences total of 54 bacteria were further studied for plant growth-promoting (PGP) characteristics. The isolates were screened to produce catalase, Indole Acetic Acid (IAA), citrate utilization, phosphate and solubilization. Fifty-one showed IAA production, 18 were found to utilize citrate and 44 were capable of degrading carbohydrates. Isolates that showed higher PGP activities were identified, which may be utilized to improve plant growth and boost crop yield.