|VAN DER GRINTEN, MARTIN - USDA-NRCS
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/10/2009
Publication Date: 2/25/2010
Citation: Sanderson, M.A. 2010. Nutritive Value and Herbage Accumulation Rates of Pasture Sown to Grass, Legume, and Chicory Mixtures. Agronomy Journal. 102(2):728-733.
Interpretive Summary: Plant species composition of pastures greatly influences herbage nutritive value. Our previous research showed that using diverse forage mixtures could increase forage yield and reduce weed invasions in pastures. A concern by farmers, however, is that large changes in the botanical composition of pastures may cause unstable and lower herbage nutritive value. In this grazing experiment, we tested the hypothesis that pastures planted to complex mixtures of forage species would be less stable in nutritive value than a simple grass-legume mixture. We studied four mixtures ranging from two to nine species. Our results showed that the number of forage species in the mixture did not control herbage nutritive value. Rather, functional group proportions (i.e., grasses, legumes, and chicory) controlled the nutritive value of mixed-species swards. Legume proportion controlled crude protein concentrations in the herbage, whereas the grass component controlled fiber concentrations. Thus, our research did not support the hypothesis that complex mixtures are inherently unstable in nutritive value.
Technical Abstract: Planting pastures to mixtures of forages may benefit herbage production; however, wide fluctuations in botanical composition could cause unstable nutritive value. A grazing study was conducted to examine how forage mixture complexity influenced nutritive value and accumulation rate during spring, summer, and autumn. In August 2001, four mixtures (two, three, six, and nine species of temperate grasses, legumes and chicory, Cichorium intybus L) were established in replicated 1-ha pastures (eight total) in central Pennsylvania. Pastures were grazed by dairy cattle from April to September of 2002 and 2003. Pastures were sampled at frequent intervals for nutritive value analysis and herbage accumulation rate in April, July, and September of each year. The three-, six-, and nine-species mixtures (all containing chicory) had 56 to 100% greater herbage accumulation rates than the orchardgrass-white clover (Dactylis glomerata L. – Trifolium repens L.) mixture in 2002, a dry year. Accumulation rates did not differ among mixtures (avg of 62 kg ha-1d-1 in spring and 47 kg ha-1d-1 in summer) in 2003 when growing conditions were better. The orchardgrass-white clover mixture had more fiber and was less digestible than other mixtures. Crude protein concentrations in the mixtures seemed to be controlled by the legume proportion in the herbage (Pearson r of 0.33 to 0.90), whereas fiber (Pearson r of 0.54 to 0.88) and digestibility were controlled by the grass proportion. There was no evidence that complex forage mixtures were inherently unstable in nutritive value compared with a simpler binary mixture.