Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2005
Publication Date: 2/7/2006
Citation: Sanderson, M.A., Brzezinski, N., Soder, K.J., Taube, F., Klement, K.D., Muller, L.D., Wachendorf, M. 2006. Sward structure of simple and complex mixtures. Agronomy Journal. 98:238-244. Interpretive Summary: Managing species-diverse (complex) mixtures of forages can be a low-input way of increasing forage productivity in pastures. In this study, we determined how forage mixture complexity affected the arrangement and distribution of forage plants in grazed pasture. We compared a simple mixture (orchardgrass-white clover) with a complex mixture of nine species that included grasses, legumes, and chicory. Our results demonstrated that complex mixtures of grasses, legumes, and chicory differed from simple grass-legume swards in the distribution and arrangement of plants in the canopy but were similar in forage quality. The differences in plant distribution and arrangement, however, did not affect forage intake or milk production of grazing Holstein cows. Therefore, producers can use complex mixtures of forages in dairy grazing systems to increase forage productivity without compromising animal performance.
Technical Abstract: Herbage intake of grazing animals is influenced by sward composition and structure. We conducted a grazing study to examine how forage mixture complexity affected sward structure. Replicated 1-ha pastures were planted to either orchardgrass- (Dactylis glomerata L.) white clover (Trifolium repens L.) or a nine-species mixture [orchardgrass, tall fescue (Festuca arundinacea Schreb.), perennial ryegrass (Lolium perenne L.), red clover (Trifolium pratense L.), birdsfoot trefoil (Lotus corniculatus L.), chicory (Cichorium intybus L), white clover, alfalfa (Medicago sativa L.), and bluegrass (Poa pratensis L.)]. Pastures were grazed by lactating dairy cows. Herbage mass, sward height, vertical structure, and nutritive value were measured pre- and post-grazing during four periods in 2002 and 2003. Pregrazing sward height was similar between the mixtures. Pregrazing herbage mass and sward bulk density were 30% less in the two-species mixture than the nine-species mixture in 2002 but similar in 2003. Cattle grazed deeper into the two-species sward (18 cm) than the nine-species mixture (11 cm) in 2003. The nine-species mixture had more herbage dry matter in the upper portion of the sward than the two-species mixture. Bulk density of herbage dry matter increased and nutritive value decreased from the top to the bottom of the sward canopy in both mixtures pre and postgrazing. Despite the differences in sward structure, herbage intake (12.9 vs. 11.6 kg d-1 dry matter) and individual animal performance (34.1 vs 34.3 kg d-1 milk) did not differ between mixtures. We conclude that at equivalent herbage mass and nutritive value the botanical complexity of grazed swards does not greatly affect herbage intake and productivity of dairy cows.