Forage Mixture Productivity and Botanical Composition in Pastures Grazed by Dairy Cattle

Some producers believe that planting pastures to several forage species benefits sustainability of grazing systems. We conducted a grazing study to determine if forage species diversity in pastures affects herbage productivity and weed invasion. One-hectare pastures were planted to four mixtures in August 2001 and then grazed with lactating dairy cattle during 2002 and 2003. The mixtures were two species [orchardgrass (Dactylis glomerata L.) and white clover (Trifolium repens L.)], three species [orchardgrass, white clover, and chicory (Cichorium intybus L.)], six species {orchardgrass, tall fescue (Festuca arundinacea Schreb.), perennial ryegrass (Lolium perenne L.), red clover (Trifolium pratense L.), birdsfoot trefoil (Lotus corniculatus L.), and chicory], and nine species [the six-species mixture plus white clover, alfalfa (Medicago saliva L.), and bluegrass (Poa pratensis L.)]. When rainfall was plentiful (2003), there were no differences in herbage yield among the mixtures; all averaged 9800 kg ha -1 dry matter. During 2002, which was dry, the two-species mixture produced less herbage than the other mixtures (4800 vs. 7600 kg ha -1 dry matter). The proportion of nonsown species in the sward was lower for the six- and nine-species mixtures than the two-and three-species mixtures, indicating less weed invasion for these complex mixtures. Red clover and chicory proportions decreased by 80% after 2 yr, and orchardgrass dominated in all pastures by May 2004. We conclude that planting a mixture of grasses, legumes, and chicory will benefit herbage production during dry years and will reduce weed invasion for a few years after planting under management similar to ours. Producers would have to reestablish the chicory and legume components relatively frequently to maintain these benefits.