Effect of timing of forage conservation on forage yield and quality, seed yield and seedling regeneration of four subterranean clover (Trifolium subterraneum) cultivars

Abstract

Swards of four cultivars of subterranean clover (Trifolium subterraneum L.) were cut at three different times to determine the effect on forage yield and quality, seed set and seedling regeneration in two successive seasons in southern New South Wales. The four cultivars of subterranean clover (Seaton Park LF, Junee, Goulburn and Clare) were cut on 23-25 September (early cut), 8-10 October (mid cut) or 22-23 October (late cut), to simulate an early silage, late silage or hay cut. Additional treatments imposed included either grazing or leaving the regrowth after cutting and raising the cutting height from 3 to 6 cm.Forage yields ranged from 3.5 to 9.3 t dry matter (DM)/ha in the first year and from 2.0 to 5.9 t DM/ha in the second year. Herbage yield was influenced by both cultivar and harvest time with the highest yields achieved with the mid cut. Lower forage yields at the later cut were attributed to losses due to respiration and decay under dense leaf canopies.Changes in forage quality were consistent across both years, with in vivo DM digestibility declining from 76-79% to 69-70% as cutting time was delayed. Crude protein fell from 22-24% to 14-17% over the same period, depending on cultivar.Seed yields in both years were influenced by both cutting time and cultivar with a positive relationship (R 2 = 0.45-0.61) between herbage present in late spring after a period of regrowth and subsequent seed yield. The early flowering cultivar Seaton Park LF had the highest seed yield in both years and the more erect cultivar Clare had the lowest. Seed yields declined with later cutting time but increased by an average of 39% when the cutting height was raised from 3 to 6 cm. Seedling regeneration reflected seed yield responses with the largest seedling regeneration occurring in treatments cut early.The study found that forage conservation in early October is likely to yield more and be of higher quality than swards cut later in the season. Seed set is greatly reduced by all cutting strategies to levels unprofitable for seed harvesting but may be adequate for pasture regeneration.

Comparative effects of grazing, herbicide or forage conservation on barley grass content in Trifolium subterraneum L. clover-based pasture

“…Also, in that experiment, cutting substantially reduced barley grass content compared with grazing, regardless of when the cutting occurred (average 0.2 vs 4.8%); which differed to our experimental results. Cutting of subterranean clover has been shown to increase seed set due to greater inflorescence numbers (Collins 1981); whereas early season cutting has been shown to increase seed yield of subterranean clover compared with later cutting (Dear et al 2008). This is supported by our findings showing differences in subterranean clover content with cutting time.…”

Pasture legumes differ in herbage production and quality throughout spring, impacting their potential role in fodder conservation and animal production

“…Maximum growth rates recorded for T. subterraneum (295 kg DM/ha) in our study was similar to that reported by Dear et al. (2008) of 287 kg DM/ha/d. The maximum growth rates recorded for B. pelecinus and T. michelianum of 300–385 kg DM/ha/d are within the range of or slightly higher than those reported by Fukai and Silsbury (1978) for T. subterraneum (300–350 kg DM/ha/d).…”

“…Furthermore, the rate at which digestibility and crude protein content declined with successive harvests, consistent with previous reports for traditional pasture legumes (e.g. Dear et al, 2008). However, some previous studies have reported de with crude protein of all entries except T. glanduliferum being >18%.…”

“…Our study found a decline in nutritional value of herbage over spring and into early summer. Decline in herbage quality throughout the growing season has been reported for T. alexandrinum , T. vesiculosum , T. michelianum , T. resupinatum , B. pelecinus , Ornithopus spp., T. glanduliferum , T. subterraneum and M. sativa (De Santis et al., 2004; Dear et al., 2008; Hoveland et al., 1972; Kaiser et al., 2007; Loi et al., 2010; Masters et al., 2006; McGrath et al., 2015; Ridley et al., 1986). Furthermore, the rate at which digestibility and crude protein content declined with successive harvests, consistent with previous reports for traditional pasture legumes (e.g.…”

“…Evans et al (2002) also reported improved winter and subsequent spring herbage production in T. michelianum where it was sown at an equivalent seeding rate (kg/ha) as larger seeded species such as T. subterraneum in an Australian study. Herbage availability is often limited in late winter and early spring (Dear et al, 2008) and can be valuable in livestock breeding systems where autumn born lambs, spring lambing ewes and pre-and post-parturient cows are in a period of high energy and protein demand.…”