Daily Light Period Influences Pod Yield, Harvest Index, and Flowering of Peanut Grown in Nutrient Film Technique

‘Georgia Red’ peanut (Arachis hypogaea L.) was grown at 8-, 12-, 16-, and 20-h light [9.3, 18.6, 13.95, and 23.9 mol m^-2 d^-1 integrated photosynthetic photon flux (PPF)] /16, 12-, 8-, and 4-h dark cycles, respectively, to evaluate effects on pod and seed yield, flowering, harvest index (HI) and production efficiency, in response to duration and amount of daily lighting. Ten-day old peanut seedlings were transplanted into rectangular nutrient film technique troughs (0.15 × 0.15 × 1.2 m) and grown for 110 days. Growth chamber conditions were as follows: photosynthetic photon flux (PPF) mean of 332 μmol m ⁻² s ⁻¹, 28°C light/24°C dark cycle, and 70 ±5% relative humidity. The nutrient solution used was a modified half-Hoagland with pH and electrical conductivity maintained between 6.5-6.7, and 1000-1200 μS cm^-1 respectively, and was replenished weekly. Foliage and pod fresh and dry weights and total seed yield increased with daily PPF up to 16-h (18.6 mol m^-2 d⁻¹) but declined at 20-h (23.5 mol m^-2 d^-1). Harvest index and production efficiency decreased with increased daily PPF. Flowering was delayed approximately 3 days as day length decreased while the cumulative number and rate of flowering increased substantially as daily PPF increased.