This field experiment was carried out to determine the effects of fertilizer application time in early spring on growth, dry matter (DM) yield, crude protein (CP) content, crude protein yield (CPY), N recovery, acid detergent fibej (ADF) content and DM digestibility (DMD) of grasses for hay. Application times of fertilizer were March 10, 20, 30, April 9. 19, and control (non-fertilized) plot was involved. The fust harvesting data for hay was May 9 (early heading stage) and the regrowth yields were investigated for soiling, 1989. In all fertilized plots, the growth, DM yield, CP, CPY and N recovery of grasses were significantly increased compared with control, and the best grass growth, DM yield, CP, CPY, N recovery and DMD were observed on March 20 and 30 among all fertilized plots. On March 20 and 30 in this experiment, the accumulated temperature was 200 and 280^{circ}C.$, and the subsoil temperature at 10 cm depth was 8 and 10^{circ}C.$. Considering the average meteorological condition in Suwon area, the optimum application time of early spring for hay may be recommended from April 10 to 15. iulcornerfW3U% (L. westock Experiment Station, RDA. Suwon 440 - 350. Korea)