Microbial enriched vermicompost efficiently substitutes soil nutrients, microbial populations and enzymatic activity for the growth and yield of tuberose (Agave amica Medik.) cv. Single.

Abstract

The aim of the study was to reduce the chemical fertilizers with microbial inoculant-rich vermicompost, which enhanced the growth, flowering, and soil health of the tuberose crop. A total of six treatments were applied with reducing doses of synthetic fertilizers under a factorial randomized design and replicated thrice. In this study, vermicompost (VC) made from cow dung and vegetable waste utilizing Eisenia foetida and their mixed biomass were enriched with microbial inoculants and assessed for their impact on microbial and enzymatic populations including urease, acid phosphatase activity and dehydrogenase activity in soil, nutrient availability, and tuberose development and flowering. The enriched vermicompost was effectively prepared through seventy- day incubation process involving rock phosphate, Azotobacter chroococcum, phosphate-solubilizing bacteria (Bacillus megaterium), and potassium-solubilizing bacteria (Frateuria aurantia). Compared with simple vermicompost, enriched vermicompost was found to be superior in terms of N, P, K, and micronutrient contents. The tuberose growth parameters revealed that treatment T₃ (8-ton enriched VC ha^-1) had the minimum number of days for 50% sprouting and the maximum number of leaves/plant among the different treatments, whereas T₅ (50% RDF ha^-1 + 4-ton enriched VC ha^-1) and T₆ (25% RDF ha^-1 + 6-ton enriched VC ha^-1) had the maximum plant height and the maximum number of shoots/bulb, respectively. With respect to the flowering parameters, plants fertilized with T₄ (75% RDF ha^-1 + 2-ton enriched VC ha^-1) resulted in a minimum of 50% blooming, and plants fertilized with T₅ presented a minimum number of days to spike visibility and opening of flowers and were superior in terms of the maximum floret and spike length, number of spikes/bulb, number of florets/spike, and vase life of the spike. Higher NP and K contents and soil microbial and enzymatic activities, such as those of soil bacteria, fungi, actinomycetes, total microbial population, urease, acid phosphatase, and dehydrogenase activities, were recorded in treatment T₃, whereas the soil organic carbon content was on par with those in treatments T₃ and T₆. This study suggests that enriched vermicompost may replace 50% of synthetic fertilizers, increase flower yield, and improve soil health of tuberose.