Sowing dates, spray scheduling, and foliar applications influence leaf biomass in soybean (Glycine max (L.) Merrill)
Sachin Nagre, Gyanendra Tiwari, R Shiv Ramakrishnan, Mrunal Ghogare, Anubha Upadhyay, RK Samaiya and Preeti Sagar Nayak
Soybean, known as the 'miracle bean', is cultivated mainly for its seeds rich in protein and oil. In India, soybean is traditionally grown as a rainfed crop during the 'Kharif' or monsoon season. Nowadays, soybean is also cultivated in the Rabi season to achieve optimal seed yield and quality. However, high-temperature conditions adversely affect crop growth, development, and yield. Elevated temperatures during critical growth stages, such as flowering and pod formation, cause reduced biomass accumulation. Hence, to test the effect of sowing window on dry matter accumulation in leaves, an experiment was conducted during the Rabi to Rabi-summer seasons at the Experimental Research Farm, Seed Technology Research Unit, JNKVV, Jabalpur (M.P), in 2021-2022 and 2022-2023. The experiment comprised 28 treatment combinations comparing two dates of sowing with two spray schedules of seven PGR treatments (T1 - Control (no spray), T2 (SA @ 250 ppm, T3 (SA @ 500 ppm, T4 (TU @ 500 ppm, T5 (TU @ 1000 ppm, T6 (CCC @ 100 ppm, T7 (IBA @ 200 ppm) were tested on soybean variety JS 20-98 using a split-split plot design with three replications. The results revealed a significant difference in dry matter accumulation in leaves at 45 DAS and 75 DAS among different sowing dates. Soybean sown in the Rabi season (D1) exhibited maximum dry matter accumulation in leaves, with an increase of 24.35% at 45 DAS and 19.01% at 75 DAS over D2 (Rabi-summer). Foliar spray during the vegetative stage increased dry matter accumulation in leaves by 4.44% at 45 DAS and 4.38% at 75 DAS. Specifically, the application of SA @ 500 ppm (T3) increased dry matter accumulation in leaves by 8.37% at 45 DAS, while TU @ 500 ppm (T4) increased it by 4.65% at 75 DAS. These findings prove that foliar application of plant growth regulators during the vegetative stage helps mitigate high-temperature stress conditions by enhancing biomass production.
