Soil temperature regimes influence leaf growth biomass of soybean [Glycine max (L.) Merrill] under rainfed condition

Abstract

A field experiment was conducted during Kharif 2024 at MARS, UAS, Dharwad, to assess the influence of soil temperature regimes on leaf growth biomass of soybean [Glycine max (L.) Merrill] under rainfed conditions. The experiment was laid out in Factorial RCBD with three sowing windows (10 July, 5 August, 9 September), two sowing depths (5 and 10 cm), and two moisture management practices (with and without mulch). Results revealed that early sowing on 10 July consistently maintained higher soil temperatures, which accelerated germination, promoted rapid leaf initiation, and enhanced leaf biomass. Sowing at 5 cm depth significantly outperformed 10 cm by providing warmer, aerated conditions favorable for seedling emergence and canopy expansion. Mulching increased soil temperature and stabilized diurnal fluctuations, further supporting continuous leaf expansion despite a marginal reduction in soil moisture. The interaction effect of 10 July × 5 cm × mulch produced the highest number of trifoliate leaves, maximum leaf area index, and haulm yield (2651 kg ha⁻¹). The study highlights that favorable soil thermal regimes during vegetative stages are critical for maximizing leaf growth, biomass allocation, and canopy development. Early sowing with shallow depth and mulching provided a synergistic environment for sustaining soybean productivity under rainfed agro-ecosystems.