Yield of binary- and multi-species swards relative to single-species swards in intensive silage systems

Abstract

Binary- and multi-species sown mixtures may increase herbage yield and/or reduce inorganic nitrogen (N) requirement compared to perennial ryegrass (PRG) (Lolium perenne L.) swards. A split-plot design was used to compare yields of binary- and multi-species mixtures to single-species swards of three grasses and red clover managed for intensive silage production under varying N application rates. Perennial and Italian (Lolium multiflorum Lam.) ryegrasses had greater annual yields when grown as single species receiving 360 kg N/ha per year than in binary mixtures with red clover (Trifolium pratense L.) receiving 0 kg N/ha per year, whereas timothy (Phleum pratense L.) produced equally high yields in both situations. When no inorganic N was applied, the annual dry matter yield of Mix 1 (10,738 kg/ha; PRG, timothy, red clover and white clover (Trifolium repens L.) and Mix 2 (11,679 kg/ha; PRG, timothy, red clover, ribwort plantain (Plantago lanceolata L.) and chicory (Cichorium intybus L.)) was greater than that of a PRG sward (PRG/0N; 5,885 kg/ha) and derived more from the contribution of legumes than herbs. This yield advantage of mixtures declined as inorganic N input increased, as did the legume and herb proportions in the multi-species swards. When averaged across rates of inorganic N input, Mix 2 had a greater annual yield than Mix 1 (12,464 vs. 11,893 kg/ha). Mix 2 receiving no inorganic fertiliser N and both Mix 1 and Mix 2 receiving 120 kg N/ha per year matched the annual yield achieved by PRG receiving 360 kg N/ha per year. Our results indicate that the yield performance of binary- and multi-species grassland swards should be measured in situ rather than predicted from single-species swards of constituent species.

Conservation efficiency and nutritive value of silages made from grass-red clover and multi-species swards compared with grass monocultures

“…The expectation that both the WSC aq and buffering capacity of the binary mixtures might be intermediate between the values for the grass and red clover monocultures did not occur, suggesting these traits differed in either or both constituent species compared with when in monoculture. This phenomenon was previously reported by Moloney et al (2020a). It may be, for example, that changes in the amount and/or timing of N provision by red clover to the grass species compared with N provision from inorganic fertiliser when in monoculture could have resulted in considerably greater WSC aq contents and lower buffering capacities for the grasses when in binary mixtures.…”

“…Field plots (each 9 m × 2 m) were established at Teagasc Grange (53.52°N, 6.66°W), and details of soil characteristics, treatment establishment and general plot management have been described by Moloney et al (2020b). The herbages used in this study were obtained from Year 1 of the (Moloney et al, 2020b) study which corresponds to the second year after sowing. Eleven treatments (Table 1) from each of four replicate blocks were used in this experiment and constituted a randomised complete block design.…”

“…Samples of herbage taken pre-and post-ensilage were stored at −18°C prior to chemical analysis. Sward botanical composition was determined on pre-ensilage samples and was reported by (Moloney et al, 2020b).…”

“…Sown multi-species grassland swards can transgressively overyield due to temporal and spatial complementarity among the sown species and also to interspecific facilitation such as the transfer of symbiotically fixed N from legumes to neighbouring species (Nyfeler et al, 2009;Finn et al, 2013;Lüscher et al, 2014). Although sward botanical composition can influence herbage chemical composition (Sanderson, 2010) the nutritive value of multi-species swards can differ from what would be expected based on the chemical composition of the component species grown in monoculture (Moloney et al 2020a;Ergon et al, 2017). This, in turn, raises the possibility that indices of ensilability and ultimately conservation efficiency may also differ from what might be predicted from values obtained for the constituent species grown in monoculture.…”

“…This, in turn, raises the possibility that indices of ensilability and ultimately conservation efficiency may also differ from what might be predicted from values obtained for the constituent species grown in monoculture. The current paper follows two earlier studies which examined the yield and botanical composition (Moloney et al, 2020b) and the nutritive value (Moloney et al 2020a) of binary and multi-species mixtures compared with a number of temperate grassland species monocultures managed under a fourcut annual silage production regime where the response of multi-species mixtures to inorganic nitrogen (N) was also determined.…”