An evaluation of tall fescue (Lolium arundinaceum) as an alternative to perennial ryegrass (Lolium perenne) for use on dairy farms in the Waikato

Abstract

Grazed pasture provides the bulk of feed on New Zealand dairy farms. As such, the amount, and the nutritive value, of the pasture grown directly influences farm production and profitability. In the Waikato (North Island, New Zealand), low soil moisture is a major constraint to pasture production and recent droughts have highlighted the limitations of the predominant pasture species, perennial ryegrass (Lolium perenne), in this region. Methods of mitigating the effects of low soil moisture include the use of drought tolerant species, like tall fescue (Lolium arundinaceum), and by using irrigation. The main objectives of this research were to compare the pasture dry matter (DM) production, nutritive value and survival of two tall fescue types (Continental, CTF; and Mediterranean, MTF) with perennial ryegrass (PR). Pastures were sown as either a grass monoculture or as grass-dominant mixtures with either white clover (Trifolium repens), red clover (Trifolium pratense) or chicory (Cichorium intybus) as companion species. The experimental design was a split block with two identical small plot experiments that were either fully irrigated (I+) or were not irrigated (I-) and were rotationally grazed by dairy cows. One experiment was established in autumn 2007 and spanned one year. A second experiment was established in spring 2008 that spanned two years, in order to determine whether productive pastures of tall fescue can be established in both seasons. Annual DM yields of I+PR pastures averaged 16.9 t DM/ha across the 3 years evaluated in this study. This was consistently greater (P < 0.003) than either I+CTF or I+MTF pastures (averaging 13.7 and 12.5 t DM/ha, respectively). Average I- DM yields were more similar at 14.5, 13.6 and 12.8 t DM/ha from I-PR, I-CTF and I-MTF pastures, respectively. Generally, PR pastures produced superior seasonal DM yields than CTF or MTF pastures, with three exceptions. In summer 2007/2008 both I+ and I-CTF pastures produced 0.6 and 1.5 t DM/ha more (P=0.004) DM than I+ and I-PR pastures, respectively. Also, in winter (P<0.001) and spring 2009 (P=0.003) I-CTF pastures produced more DM than I-PR, however, at these times an irrigation interaction was observed (P<0.001) where I+PR produced more DM than I+CTF. The enhanced I-CTF production was associated with higher tiller densities observed on I-CTF relative to I+CTF pastures that were likely a result of reduced competition from companion and weed species under low soil moisture. Irrigation enhanced annual DM yield of PR pastures (range 2–37%). While the effect of irrigation on yields of CTF and MTF was variable, ranging from a negative response (-23%) to a 16% increase, that was likely influenced by the companion species and weed content of the pastures. The addition of a companion species either reduced or produced equivalent DM yields to the monoculture pastures. While the companion species chicory contributed greatly to yield in the warmer months (December to April), this was commonly associated with a decline of sown grass yield and tiller density. Nutritive value, as defined by metabolisable energy (ME) content of herbage, from PR pastures (mean 13.0 MJ ME/kg DM) was greater than from those based on tall fescue pastures (mean 12.3 MJ ME/kg DM). However, crude protein (CP) content was greater on the CTF and MTF pastures (mean 23.9%) than the PR pastures (mean 21.5%), including the monoculture pastures (23.2 vs. 20.7% from tall fescue and PR respectively), indicating that CTF and MTF plants contain higher CP than PR plants. The ME content was largely unaffected by companion species, and the effect on CP was variable, though when differences were observed they were the result of increased CP content on the mixed pastures relative to the pasture monocultures. The magnitude of PR loss during drought was 7.5 times greater than observed on the CTF and MTF pastures. Where the decline in tiller density from I-PR pastures was 2280 tillers/m2, compared to a loss of 300 tillers/m2 from I-CTF pastures during the autumn 2009 drought, equating to a 46 and 16% reduction in tiller density from I-PR and I-CTF respectively. At both sowing times, sown grass establishment was similar. However, the less vigorous nature of the fescue seedlings allowed for higher levels of companion species in the sward relative to PR (32 vs. 13%, respectively). Although, by the end of each experiment the sown species in CTF and PR pastures dominated, signalling that both autumn and spring establishment of these pastures can be successful. The contribution of MTF to pastures was poor when sown with a companion species and by the end of the two year spring sown experiment averaged 16%, indicating poor survival. These results suggest that perennial ryegrass-based pastures are more productive and of higher quality than those based on tall fescue both in irrigated and non-irrigated conditions under dairy cow grazing in the Waikato. However, the greater companion species content and CP levels of CTF pastures and enhanced production when soil moisture was low relative to PR indicates that CTF may have a role in terms of a specialist pasture species on farm. The poor survival and yields of MTF pastures indicate that this species is not suitable for use on dairy farms in the Waikato.