Lime Or Phosphorus: Which Is Best To Lim Broomsedge In Tall Fescue Pastures?

Most Missouri tall fescue (Schedonorus arundinaceus (Schreb.) Dumort.) pastures grow on acidic, low-phosphorus (P) soils. These conditions favor increases in broomsedge (Andropogon virginicus L.), a grass that is unpalatable for livestock. Three management strategies, 1) liming, 2) P fertilization, and 3) liming plus P fertilization, were evaluated for limiting broomsedge in tall fescue pastures. An established tall fescue pasture containing broomsedge was selected in southwest Missouri (soil pH 4.6, 6 lb/acre Bray I P). Lime was applied at Ox, 0.5x, 1x, and 2x the soil test recommendation (x = 3.67 ton/acre). Plots were treated with 0 or 50 lb P/acre. Plant counts for tall fescue and broomsedge were estimated over the next 3 years. Without P fertilization, broomsedge doubled over a 3-year period. Phosphorus fertilization effectively maintained broomsedge at the initial level. The P treatment doubled the tall fescue count in 3 years following treatment, but without P, tall fescue counts remained at the initial level. Broomsedge increased nearly threefold without lime. Tall fescue more than doubled with the two highest lime treatments in 3 years. The Ox lime treatment resulted in no increase in tall fescue. Lime and P combined limited broomsedge increase to the greatest degree and produced the greatest increase in tall fescue. Increased vigor of tall fescue resulting from improved soil fertility likely influenced the increase in tall fescue and limited further encroachment of broomsedge. Applying lime and P could improve pastures by encouraging growth of desirable grasses and discouraging increases in common weeds like broomsedge.