The cereal-fallow rotation system has long been used in Central Anatolia where precipitation is low and sporadic. Replacement of fallow with Hungarian vetch (Vicia pannonica Crantz.) has proved its value to the farmers. However, the Hungarian vetch husbandry has not been well understood as a rotation crop. This study was conducted to determine whether seed and hay yield of Hungarian vetch can be improved through manipulating row spacing and seeding rates in a wheat-vetch two-year rotation system. Crop was seeded into 17.5, 35, 52.5 and 70 cm apart rows at 6, 9, 12 and 15 kg/0.1 ha seeding rates in October. Treatments were arranged in a split-plot manner design in RCBD where main plots were row spacing. Seed and hay yields were measured and results were analysed by standard variance analyses and by Modified Stability Analysis (MSA). Plots 17.5 cm row-spacing and 12 kg/0.1 ha seeding rate produced more seed than other plots when average precipitation during the growing season was less than 300 mm. If in a growing season precipitation exceeds 300 mm, seeding rate should be increased to 15 kg/0.1 ha. Higher hay yields were obtained from a plot with 52.5 cm row spacing and 12 kg/0.1 ha seeding rate in regardless of precipitation. It is concluded that narrow row spacing covers more soil surface in early season that conserves soil moisture which is utilized by plants for enhanced early vegetative growth. Rapid utilization of this soil water from narrow-spaced plots resulted in early flowering and consequently, longer generative periods contribute to higher seed yield. Wider row-spacing promote vegetative growth by decreasing shading effects of plants. A seeding rate of 12 kg/0.1 ha seems appropriate for both high seed and hay yields.