Enhancing wheat photosynthetic efficiency and productivity via co-application of humic acid and phosphate solubilizing bacteria under varying phosphorus levels

Phosphorus (P) deficiency severely constrains global wheat production, hindering photosynthetic efficiency and ultimately reducing crop yields. This is primarily due to phosphorus fixation in the soil, which diminishes the bioavailability of this crucial nutrient, thereby impairing vital functions like ATP synthesis and photosynthesis. To address this challenge, a two-year field experiment was conducted during the 2021 and 2022 rabi seasons at G.B. Pant University of Agriculture & Technology, Pantnagar, Uttarakhand (India). The study employed a factorial randomized block design with 12 treatment combinations, involving three phosphorus levels (control, 50%, and 100%, corresponding to 0, 30, and 60 kg of P₂O₅/ha) and four phosphate solubilizers (control, humic acid (HA) @ 10 kg/ha, phosphate solubilizing bacteria (PSB) biofertilizer @ 10 g/kg seed, and a combination of HA @ 10 kg/ha and PSB biofertilizer @ 10 g/kg seed). Results showed that P fertilizer application at 50% and 100% of the recommended dose significantly enhanced Soil Plant Analysis Development (SPAD) and Normalized Difference Vegetation Index (NDVI) values, particularly at 60 and 90 days after sowing (DAS). The combined application of HA and PSB yielded the highest gains in both SPAD and NDVI values, indicating improved P availability and uptake. Specifically, SPAD values increased by 8.6-12.7% and NDVI values by 2.9-8% with the combined use of HA and PSB over control. These positive findings highlight the potential of integrating phosphorus management with natural solubilizers to significantly boost photosynthetic efficiency and overall performance in wheat. This approach offers a promising, practical solution for farmers facing nutrient limitations.