Effect of biofertilizers combined with varying levels of NPK fertilizers on growth, yield, and quality of beetroot (Beta vulgaris L.) under subtropical conditions

Abstract

A field experiment was conducted during the Rabi season (November 2024–March 2025) at the Research Farm, RSM PG College, Dhampur, Uttar Pradesh, India (latitude 29.3°N), under subtropical agro-climatic conditions. The study evaluated the effect of biofertilizer inoculation combined with the recommended dose of NPK fertilizers (100:60:40 kg N: P?O?:K?O ha-1) and its reduced levels (75% and 50%) on the growth, yield, and quality of beetroot (Beta vulgaris L.). Farmyard manure (FYM @ 10 t ha-1) was applied uniformly to all plots as a baseline organic input. The experiment followed a Randomized Block Design with 18 treatment combinations and three replications. The combination of 100% NPK with vermicompost and mycorrhiza (T18) produced the highest plant height (12.37 cm at 90 DAS), superior leaf dimensions, and the highest total soluble solids (10.9 °Brix), representing improvements of approximately 54.6% and 49.3% over the FYM-baseline treatment (T1), respectively. The highest root yield in this experiment (24.95 t ha-1) was recorded in T16 (75% NPK + Azospirillum + Pseudomonas fluorescens), which was 23.8% higher than T1, indicating enhanced nutrient-use efficiency at reduced inorganic fertilizer levels. The study objectives were: (I) to evaluate the growth, yield, and quality response of beetroot to biofertilizer inoculation; (II) to assess whether biofertilizers can sustain productivity under reduced inorganic fertilizer levels; and (III) to identify the most effective treatment combination for sustainable beetroot cultivation under subtropical conditions. Further validation through factorial designs and multi-location trials is recommended.