Use of a Bioaugmented Organic Soil Amendment in Combination with Gypsum for Withania somnifera Growth on Sodic Soil

Limited availability of organic matter is a problem to sustain crop growth on sodic soil. Organic soil amendments are a cost-effective source of nutrients to enhance crop growth. A field study was conducted to evaluate the effect of an organic soil amendment bioaugmented with plant growth-promoting fungi (SFOA) in combination with gypsum on soil properties and growth and yield attributes of Withania somnifera, one of the most valuable crops of the traditional medicinal system in the world, on a sodic soil at the Aurawan Research Farm of CSIR-National Botanical Research Institute, Lucknow, India. The SFOA used was prepared by pre-enriching farm waste vermicompost with plant growth-promoting fungi before mixing with pressmud and Azadirachta indica seed cake. The application of SFOA at 10 Mg ha(-1) after gypsum (25.0 Mg ha(-1)) treatment significantly (P < 0.05) increased root length (by 96%). and biomass (by 125%) of Withania plants compared to the control without SFOA and gypsum. Similarly, the highest withanolide contents were observed in leaves and roots of Withania plants under 10 Mg ha(-1) SFOA and gypsum. Combined application of SFOA and gypsum also improved physical, chemical and enzymatic properties of the soil, with the soil bulk density decreasing by 25%, water-holding capacity increasing by 121%, total organic C increasing by 90%, pH decreasing by 17% and alkaline phosphatase, beta-glucosidase, dehydrogenase and cellulose activities increasing by 54%, 128%, 81% and 96%, respectively, compared to those of the control. These showed that application of the SFOA tested in this study might reclaim sodic soil and further support Withania cultivation and results were better when the SFOA was applied after gypsum treatment.