Arrowleaf Clover
MAJOR ATTRIBUTES
Arrowleaf Clover
- Late maturity –extends grazing period into summer.
- Deep rooting ability –exploits deep subsoil moisture.
- High dry matter yield.
- Suppression of summer weed species.
- High proportion of hard seed for persistence.
- Seed production –simple and economic.
INTRODUCTION
Arrowleaf clover, Trifolium vesiculosum, is a temperate annual legume with semi-winterdormant growth habit. Growth is most active in spring and early summer. Arrowleaf clover is recommended as a mix component with sub clovers or annual medics, rather than as a pure sward.
This species has a wide range in Europe and western Asia. It is native to Italy, Greece, Turkey, the Balkan Peninsula, the Ukraine, the western Caucases and southern Russia.
Arrowleaf clover was included in NSW pasture evaluation trials in the early 1960’s but the varieties tested lacked strong autumn-winter growth and were very late maturing. They were discarded and the research focused on annual medics, sub clovers and lucerne.
In the mid 1980’s Agriculture Western Australia began to research annual legumes for pasture land with underlying perched water tables. The interest in arrowleaf clover arose from this work and the first significant broadacre plantings of arrowleaf took place around Esperance in 1988.
In 1993, arrowleaf was included in a forage legume trial series across southern NSW. Arrowleaf clover was considered inferior to the Persian and Berseem clovers for hay or silage due to its winter-dormant habit and its thicker stems significantly increasing the dry down period for hay. However, growth from October to January made this cultivar a useful addition to pasture stands in the central west areas of NSW.
The new role for arrowleaf clover in a sub clover or medic pasture is to produce a bulk of high quality feed from moisture which is beyond the rooting depth of sub clovers, or from rain falling after the sub clovers have senesced.
Arrowleaf clover extended the grazing phase beyond that of traditional sub clover pastures by some 4 to 8 weeks into summer. This extended growth into summer provides high quality grazing and suppresses growth of summer weeds (e.g. Bathurst burr, melons and heliotrope). Arrowleaf clover has proved useful for farmers in the western wheatbelt of NSW, who wean lambs in October-November and do not have access to lucerne to provide a fresh green pick. Between 1999 and 2001, some 60,000 ha of sub clover pasture in the Central West of NSW incorporated arrowleaf clover.
In northern NSW arrowleaf is successfully utilised as a companion legume with native and naturalised summer grass pastures. This is also how arrowleaf is utilised in the USA.
Very few annual legumes can persist in the northwestern grasslands of NSW. The persistence of arrowleaf clover in these grasslands is based on its ability to grow tall, its deep taproot, high seed set and high level of hard seed.
ADAPTATION
Arrowleaf clovers are suited to temperate districts receiving at least 350 mm of annual rainfall, with a minimum of 200 mm falling between May and November. For arrowleaf clover to be a productive component of a pasture it requires a plentiful supply of moisture in late spring. So there must be useful storm rains from October to mid January or alternately moisture stored in the sub soil.
Arrowleaf clovers have grown best on loamy soils but they are adapted to sands, red-brown earths, red clays and grey clays. As clay content increases growth may be retarded to varying degrees. Preferred soil pH (CaCl 2 ) range is from 4.5 to 6.5. A pH (CaCl 2 ) greater than 7.5 may impede growth.
Heavy clay soils that are frequently inundated and remain waterlogged for prolonged periods are not suitable for arrowleaf clover.
Arrowleaf clover is predominantly a hard seeded species like rose clovers and serradellas, consequently regeneration in the second year may be low if the pasture is not grazed after the sward ‘hays-off’. Consumption of the mature seed heads by livestock often improves sward regeneration in subsequent years.
DESCRIPTION
Arrowleaf clover is an erect growing, temperate annual legume, commonly reaching one metre in height. It is semi-winter dormant, with most active growth occurring in spring and early summer.
Arrowleaf clover has a strong stem which is not prone to lodging. Its leaves are large, with distinctly arrow-shaped white markings in the middle of the mid rib (see Figure 2). The leaves contain a significant quantity of tannin which gives them a bitter taste. Sheep will frequently graze out weed seedlings before eating the arrowleaf. Insect pests also prefer to feed upon weed species. The tannin in the leaf may also reduce the incidence of bloating.
The flower heads are large with many florets being formed on a single stalk. These heads can be up to 10 cm long and 3 cm across. The less mature florets at the top of the head are white, while the more mature florets at the base take on a pink colouring.
Arrowleaf clover seed is brown in colour, slightly larger than balansa clover seed. There are approximately 800,000 seeds per kilogram. It has a high rate of hard seed (> 80%). After cleaning the hard seed level may range from 20% to 90%. A high level of hard seed is desirable for long term persistence but it can reduce short term regeneration.
Arrowleaf clover has a deep, vigorous taproot. This gives the species the ability to exploit moisture stored in the subsoil or water table and thus extends the growing season. On a freely drained, deep gravel soil arrowleaf clover roots have extended beyond 1.5 m. The actual maximum root depth is yet to be established.
VARIETIES
Zulu:
Zulu was developed in South Africa, where it out performed the three cultivars developed in the USA. Zulu has a vernalisation or cold requirement and usually flowers after 151 days in a glasshouse, but it is commonly 200 days in the field. Zulu usually flowers from mid November. Plants growing from a spring germination of seed may not flower for 12 months or longer. The plant commonly grows from 70 cm to 80 cm tall; individual plants can exceed one metre in height. Zulu is a public variety and farmers are able to sell seed to other farmers.
Seelu:
This variety was selected from Zulu by the South Australian Seed Cooperative in 1991. Seelu matured about 2 days earlier than Zulu in glasshouse trials in Perth. Seed lots are uncommon. Seelu is a public variety.
Cefalu:
It was a single plant selected from a commercial Seelu seed lot by Western Australian Department of Agriculture in 1997. Plants are usually only 50 cm to 60 cm tall and much finer than Zulu. Cefalu matures 20 to 30 days earlier than Zulu. Cefalu tends to senesce by mid November, about four weeks after Dalkeith sub clover and does not continue to grow-on like Zulu in a wet summer. Cefalu is protected by Plant Breeders Rights for Seed Grain and Biotechnology Australia. Farmers can only produce seed for use on their own farm.
Arrotas:
This variety was bred from an Italian accession by the Tasmanian Department of Primary Industries and Fisheries and registered in late 1996. Arrotas matures 30 days later than Zulu in glasshouse trials. It has a slightly thicker stem than Zulu and is up to 20 cm taller than Zulu in glasshouse evaluation. Arrotas has smaller leaves than Zulu. Arrotas is protected by Plant Breeders Rights for Tas Global Seeds. Farmers can only produce seed for use on their own farm.
