GDU = (Tmax + Tmin)/2 − Tbase
Growing Degree Units (GDU) or Growing Degree Days (GDD) quantify heat accumulation for predicting crop development stages. GDU = (Tmax + Tmin)/2 − Tbase, with caps: Tmax capped at 86°F and Tmin floored at 50°F (for corn). Base temperature varies by crop: corn 50°F, wheat 40°F, cotton 60°F. Corn milestones: emergence 120 GDU, silking 1400 GDU, maturity 2700 GDU. Accumulated GDU from planting predicts when each growth stage will occur, helping farmers schedule irrigation, fertilization, and pest management. GDU is more reliable than calendar days because it accounts for actual growing conditions.