Novel Grazing

September 2005
The Ryegrass and white clover association is the overwhelmingly dominant pasture in New Zealand, but clover content rarely gets above 20%. The association is very valuable to farming, with clover contribution that has been estimated as $2 billion pa worth of Nitrogen fixation, enabling the ryegrass to flourish without the large fertiliser nitrogen inputs used in other countries. The clover legume fixes Nitrogen and supplies it to grass. They also have complementary patterns of seasonal growth, ryegrasses more productive in autumn, winter and spring, and clover potentially given adequate water more productive in summer. They are also complementary in nutritional aspects, clover is high in protein, which is rapidly degraded in rumen, and grass has a higher concentration of fibre. Indeed, studies worldwide show, the greater percentage of clover in pasture, the greater the intake of dairy cows, and the greater the milk yield, although this appears to flatten out around 60-70%.

However this dual association has drawbacks:

Lack of pasture species diversity.

At 20% of pasture, the clover nitrogen inputs are too low for maximum ryegrass production.

The energy available to grazing animals is below optimum.

Applied nitrogen to make up the clover deficit has environmental concerns.


Caucasian clover is an alternative for white clover, being deeper rooting, strong spring and summer growth and improved tolerance of water stress and pests and diseases.

After a slow establishment, Caucasian clover and ryegrass pastures have been shown to be up 9% higher yielding and with legume content up to 50%.

Species such as phalaris and tall fescue have deeper roots than ryegrass, with lucerne having the deepest roots of all. It can reach 20-25 tonnes/ha, considerably in excess of ryegrass and clover.

Methane emissions for livestock remain an issue and from a pastures point of view there is interest in whether methane production can be reduced by grazing livestock on plants such as lotus and sulla which contain condensed tannins. In addition to preventing animals from getting bloat, tannins also prevent forage proteins from being degraded in the rumen, enhancing digestion, and improving milk yield. Cows grazing lotus had a 30% increase in milk yield and a 18% reduction in methane and per kg DM consumed compared to perennial ryegrass, emphasizing the value of condensed tannins.

Although these plants may have improved functions, they generally are viewed as having some drawback, slow establishment in caucasian clover and difficulty of management with lucerne. Ryegrass-white clover, supported with the use of N in spring and autumn will remain the default, particularly under irrigated conditions.

So it is appropriate to ask how might we get a little more out of ryegrass-white clover pastures, in particular, how might we get the legume to contribute more.

Dr Grant Edwards, senior lecturer of the Animal and Life Sciences Division at Lincoln University, has researched alternative establishment strategies for ryegrass and clover, growing them separately in blocks, strips or alternate drill rows.

He has also looked at separate morning and afternoon grazing and seasonal variations, all designed to boost the clover persistence and animal intake.

The grass-clover association is also a story of competition for space, light and nutrients. As clover increases in abundance, more N is fixed, soil N builds up which is ideal conditions for the grass. The grass is competitive and drives the legume to low abundance. Lacking legume, the grass becomes N deficient and less competitive, and the clover begins to rise again.

Growing grass and clover separately may also lead to grazing them separately, allowing the animals to express their preference. Using automatic recording systems for free ranging cows, it has been found that cows, along with sheep and goats, prefer a diet of 70% clover and 30% grass. So in experiments when cows are placed in paddock that is half grass and half clover, they select diet of 70% clover/30% grass even though a diet of total grass or total clover could easily be obtained. Furthermore, they show a diurnal pattern of preference, preferring clover in the morning and grass in the evening. So 50-70% of clover in the pasture is required, way ahead of what is common in association with ryegrass.

When they are grown separately, but side-by-side, the content could be presented in ratios which closely match the partial preference of animals. They would also gain considerably more energy from the feed intake. Separation also removes the competition between grass and clover and allows targeting of management inputs to one species or the other, e.g. nitrogen fertiliser to grass. Also about 70% of the nitrogen available to grass from the clover association actually comes through the air, not by close association of their roots underground.

Various studies in the UK have shown milk production increases for ryegrass and clover separation, versus in association. Up to 20% extra may be available through novel grazing, a steep change in production which would be very hard to obtain through continuous improvement and genetic gain.

New Zealand is no longer the lowest-cost dairy producer, but it can regain that advantage by being smart with novel grazing.