Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 20, 2002
Publication Date: November 20, 2002
Citation: SANDERSON, M.A., ELWINGER, G. PLANT DENSITY AND ENVIRONMENT EFFECTS ON ORCHARDGRASS WHITE CLOVER MIXTURES. CROP SCIENCE. 2002. v. 42 p. 2055-2063. Interpretive Summary: White clover is a critical component of mixed species pastures. Maintaining a productive grass-clover mixture in grazed pastures depends on the soil type, environment, plant density, and compatibility of specific grass and legume varieties. The objective of this field study was to examine how soil type, orchardgrass cultivar, and grass plant density affected the structure, yield, and competitive interactions between orchardgrass and white clover. Plant comeptition, soil factors, and climate interacted to govern the number, size, and structure of white clover stolons in this study. The results indicate that on productive soils, management should focus on controlling the height of the grass canopy to enable the white clover to compete for light and maintain a productive stolon population. On less productive soils, management should address amendments to improve fertility when economically feasible. Soil physical limitations, however, such as excessive drainage or shallow soil with low water-holding capacity, may limit plant responses to amendments. Therefore, management of grass-clover mixtures on these sites should focus on reducing weed pressure so that bare soil and canopy gaps can be colonized by white clover stolons.
Technical Abstract: Competitive interactions between grass and white clover are affected by the grass and legume cultivar used, density of grass and legume plants, and the environment. We conducted a field study to examine how these factors interacted in orchardgrass (Dactylis glomerata L.) and white clover (Trifolium repens L.) mixtures. `Dawn' and `Pennlate' orchardgrass were established at 10, 20, or 40-cm spacings in mixture with `Will' white clover. A systematic plant spacing design was used (a Nelder fan design). The experiment was established in September 1996 at three sites in Pennsylvania of different soil type (Hagerstown, Berks, and Rayne soils) and elevation (300 to 600 m above sea level). Orchardgrass was harvested monthly from May to September 1997 and 1998 to determine dry matter yield and tiller number per plant. White clover plants were dug from each plant spacing and site in October 1997 and 1998 to determine the number, length, and mass of main stolons and first- and second-order branches. Increasing grass plant density reduced tillering and increased competition with white clover. Orchardgrass cultivar did not affect white clover stolon structure. On the Hagerstown soil, there was a three- to four-fold increase in the number of main stolons along with first-order branches as spacing between grass plants increased. The highest stolon densities occurred at the 40-cm plant spacing on the Hagerstown soil in 1998 where there was more than 22 m of main stolon m-2 along with 8 m of first-order branches and 1 m of second-order branches. On the Rayne soil, plant spacing had little effect on stolon structure. Orchardgrass and white clover plants were larger and more complex on the Hagerstown soil than on the lower fertility Berks and Rayne soils. Weed competition was greater on the lower fertility Rayne soil (788 plants m-2 from 33 species) than on the higher fertility Hagerstown soil (157 plants m-2 from 19 species). The combination of low soil pH, low available soil P, and limited waterholding capacity of the Berks and Rayne soils along with weed competition resulted in small, less highly branched white clover plants.