An upright perennial dicotyledon herb with a coarse, fibrous root system, plantain grows throughout NZ on a wide range of soils, including those of low fertility, but isn't suited to waterlogged or saline soils.
Modern forage plantain can respond to good management by expressing a production potential similar to perennial ryegrass when newly established.
As plantain has a tolerance to summer heat, it can provide valuable forage and improve milk production in warmer and drier regions.
In the past five years, studies have shown the cultivar Ceres Tonic significantly reduces nitrogen concentrations in cattle urine, which in turn reduced the nitrate leaching risk in dairy systems.
The Forages for Reduced Nitrate Leaching and Greener Pastures research programmes are determining the optimum dietary levels and how to achieve them in farm systems. Good establishment and management of forages containing plantain will be critical to getting the maximum benefit.
Plantain can be sown as a pure sward, mixed with clovers and other herb species or mixed with grass and clover.
Which type to use depends on the intended purpose. In all situations, plantain is best established by sowing at 10mm depth, into a cultivated seedbed or direct drilling seed into herbicide-treated pasture, when soil temperature is over 10C.
The only field trial directly comparing methods showed direct drilling, while more costly than broadcasting seed, more than made for it with denser plant populations, lower weed content and increased yield.
The sowing date will depend on the temperature and moisture conditions dictated by region and soil type. Although we lack direct comparisons, both autumn and spring sowing have been successful, and summer sowing is an option if irrigation is available.
For spring sowing, planting too early risks a late frost damaging young plants, while planting too late risks dry conditions reducing plant survival.
On winter-wet sites, a spring sowing after spraying with glyphosate, light cultivation and drilling is likely to be most successful.
For autumn sowing, planting too early risks poor germination in summer-dry conditions, while planting too late may not ensure sufficient leaf growth and root development before cooler winter temperatures arrive, and risks the first grazing being in wet and cold conditions.
As a pure sward
The main advantage is that it can be managed to meet the requirements of the plantain cultivar. Optimal sowing rates for pure swards are 7-10kg/ha. Plants should have a minimum of six fully developed leaves before they are ready for the first grazing, to ensure a well-developed root system.
Grazing management strategies designed to maximise quality and quantity of plantain crops aim to maximise leaf growth and minimise stem growth. An 8-25cm height is recommended because, as plantain leaves age, they become more fibrous, less digestible and the quality declines.
The main disadvantages of a pure sward are poor winter growth compared with perennial ryegrass and the relative sensitivity to pugging and winter damage.
In a herb-based mix
The main advantage is the high forage quality from combining plantain with chicory and/or clovers. Optimal sowing rates are 6-8kg/ha for the plantain component, with the other species making up an additional 10-12kg/ha.
The guideline of first grazing at the six-leaf stage also applies to herb mixes and swards be grazed to 8cm-plus residual heights with four-week intervals. For dairy cows, the main disadvantage of this forage type is the risk of bloat.
In a grass-based mix
Plantain improves the summer quality and autumn recovery of perennial ryegrass pastures, especially in summer-dry environments. Optimal sowing rates are 2-4kg/ha, any lower has a minimal benefit for herbage production10.
Plantain in a ryegrass pasture mix is necessarily managed as with a ryegrass- white clover pasture (grazing to residuals of 1500-1600kg DM/ha), which is within the tolerance of plantain.
Plantain can be drilled or broadcast into already established pasture, although establishment is slower and plant populations may not reach the density required to affect urinary nitrogen concentration. The recommendation to graze at six developed leaves does not apply, as this will be too long a rotation for the grass and will shade out the plantain seedlings.
Challenges for management
The main ones are maintaining plant population density, control of broad leaf weeds and sporadic palatability issues. A substantial reduction in plant numbers can occur after two to four years, so plantain is often regarded as a short-lived perennial. Only one study (in Northland) has reported contributions of plantain in mixed swards greater than 15per cent of total forage dry matter after four years.
When plant populations have been measured, the decline has often occurred in the second summer-autumn and is often associated with insect pests. Severe outbreaks of plantain moth infestation can occur in pure swards, which can be controlled with insecticides Exirel or Minecto Star.
Plants appear to be mainly lost through competition from other species, short grazing rotations and from treading damage on wet soils. While tolerant of low grazing residuals, it must be allowed to recover to six leaves (about 25cm in height) for critical root reserves to be replenished.
Plantain is a prolific seeding plant and new plants can establish from natural reseeding under rotational grazing. A detailed Manawatu study showed new plants making up 14per cent of growing shoots from natural establishment over winter and spring.
Stock will avoid eating seed heads and germination occurs quickly with sufficient moisture and warmth, though seedling survival is best in bare ground and competition is limited. However, to maintain plant populations at a level sufficient to ensure plantain is a high proportion of the cow's diet, under-sowing by drilling or broadcasting plantain seed in spring may be necessary.
It is wise to eliminate weeds as thoroughly as possible before sowing, as most post-establishment herbicides harm plantain. Only two products are registered, Dynamo can be used in grass-based mixtures and T-Max can be used in pure plantain crops or mixtures without clover.
Plantain cultivars available largely differ in flowering dates and seasonal growth rates but there is currently no published information on their relative efficacy in reducing urinary nitrogen concentration. There is little evidence that establishment requirements differ between cultivars, although late autumn sowing of winter-dormant cultivars should be avoided.
* Plantain can be established as a pure crop, in a herb or grass-based mix.
* Plantain establishes well in most regions and soils, and late spring sowing by direct drilling generally results in the best first-year yield.
* Frequent grazing and treading damage in winter will reduce plant density. Resowing after two to four years may be required to maintain a high proportion of plantain in the pasture.
* Two herbicides are now registered for use with plantain — Dynamo in mixed pastures and T-Max in forages without clover.