Microsite management for enhancing root yield and quality of ashwagandha (Withania somnifera (L) Dunal)

Abstract

The winter cherry (Withania somnifera (L.) Dunal), often known as Indian Ginseng, is an annual herbaceous medicinal plant belonging to the Solanaceae family. The Sanskrit name ashwagandha was given to this plant due to the smell of the roots resembling a sweating horse. Though all the plant parts are rich in secondary metabolites, roots constitute a significant part of the trade. Ashwagandha roots are rich in bioactive compounds like steroidal lactones, alkaloids and flavonoids. Recognizing its market potential, the National Medicinal Plants Board, India, has endorsed its commercial cultivation. Ashwagandha cultivation has good potential in Kerala due to high market demand. As it is a new crop in Kerala, before recommending it for commercial cultivation, it is necessary to standardize the nutrient management practices to ensure high yield and quality. The present study was undertaken from August 2023 to January 2024 in the Department of Agronomy, College of Agriculture, Vellanikkara, to assess the effect of organic manures and biostimulants on the growth, yield and quality of Ashwagandha (Withania somnifera (L.) Dunal). The experiment was laid out in Factorial Randomized Block Design (FRBD) and replicated thrice. The treatments consisted of four levels of organic manures viz., FYM @ 5 t/ha, FYM @ 10 t/ha, vermicompost @ 2.5 t/ha, vermicompost @ 5 t/ha and four levels of biostimulants viz., water spray, seaweed extract @ 0.4%, humic and fulvic acid @ 0.4%, and chitosan @ 0.1%. The total quantity of organic manures was given as basal, and biostimulants were sprayed at one and three months after planting (MAPs). Organic manures and biostimulants significantly influenced the plant height, number of branches/plant, fresh biomass and dry biomass/plant. A higher number of roots were observed in plants with vermicompost @ 5 t/ha (4.62) and seaweed extract (4.91). The dry weight of roots per plant was recorded maximum in plants with vermicompost @ 5 t/ha (3.22 g) and seaweed extract (3.59 g). Interaction between organic manures and biostimulants was also significant concerning dry root weight per plant. The treatment combination of vermicompost @ 5 t/ha and seaweed extract gave a higher dry root yield of 4.79 g/plant. Organic manuring and biostimulant application significantly influenced physiological and biochemical parameters. However, total chlorophyll content was unaffected throughout the growth stages. Higher total alkaloid content was observed when vermicompost was applied @ 5 t/ha (2.07 %) and the lowest was noticed in FYM @ 5 t/ha (1.62 %). Plants sprayed with seaweed extract recorded the highest total alkaloid content of 2.17 % among different biostimulants. Crop growth rate (CGR) and relative growth rate (RGR) were higher in plants that received vermicompost @ 5 t/ha and seaweed extract. At all the stages of observations, organic manures do not significantly influence the relative leaf water content of ashwagandha plants. However, biostimulants considerably increased the relative leaf water content at 60 and 120 DAP. Enhanced N, P and K uptake was observed in plants fertilized with vermicompost @ 5 t/ha. The soil organic carbon content increased in FYM @ 10 t/ha (1.36 %) applied plots compared to pre-experimental status (1.11 %). Significantly higher soil microbial biomass carbon was found in plots fertilized with FYM @ 10 t/ha (258.56 mg kg-1). Soil available N, P and K were higher in the soil that received the same treatment. A higher B:C ratio of 2.25 was realised from the treatment combination of FYM @ 10 t/ha along with foliar application of seaweed extract, followed by FYM @ 5 t/ha with humic and fulvic acid (2.15). The lowest B:C ratio of 0.39 was noticed in the treatment combination vermicompost @ 5 t/ha with humic and fulvic acid. The study revealed that the growth and yield of ashwagandha can be improved through organic nutrient management. Applying basal application of vermicompost @ 5 t/ha boosted growth and yield. Supplementing this with seaweed extract as a foliar spray at 0.4% enhanced the quality. While combining vermicompost and seaweed extract optimized crop growth, yield and quality, the most profitable combination comprised FYM @ 5 t/ha with seaweed extract spray.