Establishment and Management
Sowing
Arrowleaf clover cannot be successfully grown with a cereal cover crop. In most years the spring growth of the arrowleaf will impede the harvesting of the cereal crop.
Arrowleaf is best established by one of three methods –as an elite sward, drilled into existing pasture when that pasture is dormant, or broadcast onto a cover cropped pasture post-harvest and having the seed walked into the soil by sheep as they scavenge for spilt cereal grain.
Elite swards are sown from early April to late June into a well prepared seedbed. Use trifluralin to control wireweed, fumitory, annual grass weeds and volunteer cereals. Arrowleaf is sown with sub clovers or medics. Sow 1 kg/ha of scarified arrowleaf clover seed with 5 kg/ha of sub clover or medic seed into a moist soil with a fine tilth to a depth of no more than 1 cm.
Inoculate arrowleaf seed with rhizobia group C inoculum. Drill at least 10 kg/ha of phosphorus when sowing any clover pasture. In some districts additional sulphur may also be required.
Existing sub clover pastures are usually renovated by direct drilling with arrowleaf, but it is necessary to increase the seeding rate to 2 kg/ha. In southern tablelands and districts with rainfall exceeding 700 mm, arrowleaf clover has been successfully established from aerial seeding.
Grazing
Grazing may commence when the clover plants are securely anchored. This usually occurs about six weeks after emergence.
Newly sown paddocks should be destocked from the onset of flowering to maximise seed set. Stock may be reint
roduced 6 to 8 weeks later, once the seed is well developed, at half the normal stocking rate. Once the pasture has dried off, increase the stocking rate to consume the seed heads and to remove as much residue as practical.
Observations suggest that a reasonable proportion (>80%) of the seed consumed by sheep will pass through the gut undamaged and is therefore capable of germinating.
Second year pastures should be grazed normally at standard stocking rates. Avoid crash grazing with high stocking rates particularly when the arrowleaf clover is running up to flower as it can reduce productivity over summer as seen in figures 4 and 5. These plots were harvested using a lawn mower which simulates crash grazing. The unmown Zulu plants outside the plots continued to grow through to late December.
NUTRITIONAL QUALITY AND ANIMAL PRODUCTION
Arrowleaf clover produces abundant herbage which is high in protein (up to 30%), and remains highly digestible for a long time relative to other legumes as seen in Figure 3. This is due to its late maturity and deeper rooting habit and its ability to respond to later spring and summer rain.
Dry matter production from arrowleaf clover varies widely depending on variety (see Figure 4), soil type, availabl
e nutrients, prevailing warm conditions and early summer rains.
Sub clover pastures incorporating Zulu in the southwest wheatbelt (see Figure 5), have been capable of producing over 6,000 kg/ha of feed (dry wt.) in a typical year receiving 40 mm of rainper month. In comparison a typical sub clover pasture produced around 5,000 kg/ha. In this trial the arrowleaf fortified pasture plots trade off some early autumn growth but have additional forage in October and November. The Zulu outside the harvested plots produced approximately another 1,000 kg of feed/ha during December.
In the higher rainfall districts of the southern slopes forage yields have been reportedly as high as 9.0 t/ha in good seasons.
Regeneration
Poor regeneration rates in the second year have been reported as a limiting factor for arrowleaf clover. Grazing should be managed to maximise seed set and regeneration in the following season.
The grazing strategy should aim to maximise seed set in new swards.
Consumption of the seed heads by livestock aids subsequent germinations.
It is worth noting that the drier the conditions are during seed set and seed fill the greater the hard seed percentage.
Some farmers have harvested small quantities of their own arrowleaf seed, they then scarify the seed and then broadcast it onto pastures in late summer to ensure satisfactory regeneration in the following autumn.
ANIMAL HEALTH
Arrowleaf is not sown as a pure sward by farmers, is usually mixed with sub clovers or medics. Therefore it is prudent that farmers observe the usual management protocols for sub clover and medics to minimise livestock disorders like bloat, red gut, foot scald and clover/kidney stones.
While arrowleaf foliage contains tannins that reduce the incidence of bloat it would be unwise to depend on that potential in a mixed sward.
INSECT PESTS
Red legged earthmites and lucerne flea can cause significant injury to seedling plants, although once arrowleaf clover is well established it appears to have reasonable tolerance or lack of appeal to these pests because of the tannins contained in its leaves.
Bluegreen aphids have been found in arrowleaf clover in Western Australia but have only caused minor damage. In the USA cowpea aphid, pea aphid, potato aphid and the green peach aphid have been found feeding on the flowers of arrowleaf clover.
DISEASES
Arrowleaf appears to be resistant to clover scorch disease, but may be susceptible to Phytophthora root rot under waterlogged conditions.
Bean Yellow Mosaic Virus is a significant disease that affects most legume species and arrowleaf is no exception. USA reports have also noted Pepper spot and powdery mildew but their instance is uncommon. Cercospora leaf spot has also been suspected in the USA.
Red Leaf Virus has also been identified in arrowleaf plants in Western Australia.
WEED CONTROL
Sub clover based pastures are commonly sprayed with MCPA 500 amine* to control broadleaf weeds. Like most
Trifolium species arrowleaf will tolerate MCPA amine.
Do not use herbicides or mixtures containing bromoxynil, terbutryn, diflufenican and 2,4-D amine as
significan
t injury to the arrowleaf clover (dry matter reduced by 70% or greater) can be sustained.
*In NSW only Generex MCPA 500® and AH Marks Agroxone MCPA 500® are registered for use in sub clover pastures.
SEED POTENTIAL
This species lends itself well to seed production, particularly where seed is required for use on the same property. Surplus seed of the public variety Zulu may be sold to other farmers, but all other varieties are protected by Plant Breeders Rights in Australia.
Areas intended for seed production should be closed up in spring. Arrowleaf can be readily harvested with an open fronted header. The stand should be harvested as soon as the majority of the seed is mature. Some seed may shed if harvesting is delayed. Seed yields have ranged from 200 kg/ha to 400 kg/ha from pasture stands in NSW but specialist seed producers in South Australia have recorded consistent seed yields of 1,000 kg/ha. The highest seed yield recorded to date was 1,400 kg/ha of seed on a farm to the north of Perth.
