Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/26/2003
Publication Date: 5/20/2004
Citation: Sanderson, M.A., Elwinger, G. 2004. Emergence and seeding structure of temperate grasses at different planting depths. Agronomy Journal. 96(3):685-691. Interpretive Summary: Recommended sowing depths for temperate forage grasses, such as perennial ryegrass and orchardgrass, range between 1 to 1.5 cm. Improper sowing depth can result from poorly packed seedbeds, uncalibrated equipment or the belief that seeds planted deeper in the soil may have greater chances of intercepting soil moisture. Producers need better information on the emergence, establishment, and development of many perennial grasses to establish productive multispecies swards. We conducted growth chamber and greenhouse experiments to examine seedling morphology when planted at several depths and conducted two field experiments in different environments to verify responses. Our results suggest that perennial ryegrass, a relatively large seeded species, should not be the dominant species in a mixture because it could compete strongly against smaller seeded species. Our research demonstrates that proper control of planting depth is critical in establishing multi-species forage mixtures. When planted at 3 cm depth, average emergence of grasses was 64% in July and 33% in September. Thus, relatively small variations in planting depths along with differences in seedling development rates of grass-forb mixtures could result in wide variations in final emergence and ultimate sward composition.
Technical Abstract: Manipulating plant species diversity in managed grasslands affects productivity and ecosystem stability. Grass seedling emergence and structure under different planting conditions must be understood to develop planting recommendations for multispecies swards. We conducted controlled environment and field studies to compare the seedling emergence and morphology of several grasses from three planting depths. Perennial ryegrass (Lolium perenne L.; diploid and tetraploid cultivars), orchardgrass (Dactylis glomerata L.), prairiegrass (Bromus catharticus Vahl) and bromegrass (Bromus stamineus Desv.) were planted at 1, 3, and 6 cm in the growth chamber and greenhouse and seedlings were destructively sampled 14 d after emergence. Leaves, tillers, and roots were counted. Mesocotyl and epicotyl length and coleoptile width were measured. The grasses were planted in two field experiments to determine emergence and seedling size when planted at 1, 3, or 6 cm. Both perennial ryegrass and orchardgrass elongated the mesocotyl and epicotyl but bromegrass and prairiegrass did not. Seedlings of bromegrass and prairiegrass had greater mass but fewer tillers and roots than perennial ryegrass. Increased planting depth reduced seedling size by reducing the number and size of leaves and number of tillers by 15 to 30% in all grasses. Deeper planting reduced emergence and seedling size in the field. Differences in seedling size and structure among cultivars within species were positively correlated (r of 0.8 to 0.9, P < 0.05) with seed mass. Seed mass, however, did not explain differences in seedling emergence in the field. Planting depth affects the emergence and growth of these cool-season grasses similarly.