Effect of plant density on forage yield and quality of intercropped corn and lablab bean

Low crude protein (CP) concentration in corn (Zea mays L.) silage is its major dietary limitation in dairy rations. In this experiment, four densities of corn (20,000, 40,000, 60,000, and 80,000 plants ha(-1)) and four densities of lablab bean [Lablab purpureus (L.) Sweet] (0, 40,000, 80,000, 120,000 plants ha(-1)) were intercropped to determine the optimal planting density in terms of forage yield, nutritive value, estimated milk production, and forage nutrient value. Experiments were conducted near Arlington and Lancaster, WI. Corn was sown in late April and lablab bean was sown in rows 8 cm beside corn rows 2 wk after corn planting. Averaged over locations, forage dry matter (DM) yield ranged from 11 Mg ha(-1) to 20 Mg ha(-1) as corn plant density increased from 20,000 to 80,000 plants ha(-1). Lablab bean increased CP concentration by 22 g kg(-1) DM between corn densities of 80,000 plants ha(-1) and 20,000 plants ha(-1) at a bean density of 120,000 plants ha(-1). Calculated milk ha(-1) values ranged from 17,500 kg ha(-1) to 34,400 kg ha(-1) as corn plant density increased from 20,000 to 80,000 plants ha(-1). This experiment does not show benefit to addition of lablab bean into high producing corn stands. Corn sown at a density of 80,000 plants ha(-1) and 0 bean plants ha(-1) is recommended to maximize forage DM yield, milk ha(-1), and crop value. Alternatively, addition of lablab bean into low density corn stands did increase CP concentration and feed nutrient value of the forage.