Bacterial derived biopolymer to alleviate nutrient stress and yield enhancement in turmeric (Curcuma longa L.) by mediating physiology and rhizosphere microbes on poor soils of semi-arid tropics

Biopolymers (BP) are the unexploited eco–friendly microbial derivatives which regulate soil moisture and nutrient mobility. Therefore, a field experiment was conducted for two years (2017–18 and 2018–19) to determine the beneficial effects of BP in reducing nutrient stress and yield enhancement in turmeric. The study was laid out in a split-plot design with each of four levels of nutrients (control, 50%, 75%, and 100% of Recommended Dose of Nutrients; RDN) and BP (0, 2.5, 5.0, and 7.5 kg ha^–1). Results indicated that BP application (7.5 kg ha^–1) significantly improved the soil moisture content (40.31%) and microbial colonization (total microbes, N fixers, and P solubilizers). As a result, combined application BP with either 75% or 100% of RDN enhanced the photosynthesis (22.95–24.50 μmol m⁻² s⁻¹) and lowered the canopy temperature (24.47–24.67°C) of turmeric. Thus, higher yield (7.05–7.82 t ha⁻¹) and partial factor productivity were achieved. Supplementing BP with 100% RDN enhances the turmeric yield by up to 29–49% over 100% RDN alone. Therefore, biopolymer maintains the equivalent turmeric yield of 100% RDN even at 25–50% less nutrients in the nutrient-poor soils of semi-arid Tropics.