Seasonal Variability in Thermal Indices and Heat Use Efficiency of Maize under Varietal and Nutrient Management in Tarai Region of Uttarakhand, India

Abstract

Maize (Zea mays L.) growth and productivity are strongly influenced by temperature and seasonal climatic conditions that regulate crop phenology and thermal energy utilization. However, limited information is available on seasonal variability of thermal indices and heat use efficiency of maize under different varieties and nutrient management practices in the Tarai region of Uttarakhand. Therefore, a field experiment was conducted at the N.E. Borlaug Crop Research Centre, Pantnagar during the winter (November 2024-April 2025) and spring (February-June 2025) seasons to evaluate seasonal effects on thermal indices, phenology and heat use efficiency of maize. The experiment was laid out in a split-plot design with three maize varieties (PCM-04, DKC-9081 and DKC-9188) as main plot treatments and four nutrient management levels as subplots: T1-control (no fertilizer), T2-vermicompost (80:20), T3-poultry manure (80:20) and T4-recommended dose of inorganic fertilizers (RDF). Temperature-based indices including Growing Degree Days (GDD), Heliothermal Units (HTU), Photothermal Units (PTU) and Heat Use Efficiency (HUE) were computed. Spring maize accumulated higher thermal units (GDD 1691.45 °C Day, HTU 14327.25 and PTU 21830.23) and recorded higher grain yield (9373.04 kg ha⁻¹) than winter maize (GDD 1303.38 °C Day, HTU 9824.29, PTU 14733.81; yield 7305.00 kg ha⁻¹). Spring maize also matured earlier (92-110 days) compared to winter maize (132-151 days). The treatment V₃F₄ (DKC-9188 with RDF) recorded the highest grain yield and heat use efficiency in both seasons. The results indicate that improved varieties combined with optimum nutrient management enhance thermal resource utilization and maize productivity under different seasonal environments.