Pastures are mixed communities of plant species adapted to being grazed.

All pastures are not the same, as every farmer in the world knows.

New Zealand farmers have at their disposal a wide range of pasture species which they utilise for livestock grazing, and may also harvest and store for later use.

More than 100 certified cultivars are available in more than 20 different grass, legume and herb species, along with more than 30 cultivars belonging to six brassica species.

The point of developing a range of pasture plants is to extend the growing season, produce more dry matter and lift the metabolisable energy (energy available to ruminant animals from pasture or other feeds).

When pasture is the only source of feed for your cattle, sheep and deer, then you want the best quality pasture that science can provide for your farm, climate and finances.

Research and selection pressure on pasture cultivars in New Zealand have resulted in a range of highly productive and well-adapted grasses, legumes and herbs for livestock consumption. These are often grown in site-specific combinations for maximum dry matter and energy production.

Commercial quantities of seeds, patented under the Plant Varieties Act, have been produced under strict growing and dressing regulations, and are backed by purity and germination certificates. These are exported from New Zealand to provide seed companies and farmers in other countries the opportunity of a New Zealand pastoral boost to local farming methods.

Detailed agronomic and animal nutrition advice is also available, and many New Zealand trained pastoralists currently work in farming industries of other countries. 

Pasture-based livestock systems have been developed and refined in New Zealand to minimise farm labour requirements and get maximum productivity from improved genetics.

Since the coming of Europeans to New Zealand in the early 19th century, nearly 10 million hectares of grassland have been established, which was originally native forest, scrub and fern or native tussock.

The basic unit in New Zealand agriculture is the family farm, run by the farmer with family and/or part-time assistance. Machinery ownership on farm is deliberately kept low, with many pasture renewal, fodder conservation, crop establishment and harvesting tasks performed by contractors.

New Zealand farming now offers a viable alternative to the high-input, heavy machinery, housed livestock farming systems in developed countries, dependent on government subsidies for crop in puts and storage and product exporting. 

Low-cost options can be adapted to local conditions, animals and crops, using New Zealand agricultural equipment and consultancies.

In recent years New Zealand has pushed out the boundaries of all-grass pastoralism, particularly for dairying, by combining a moderate and strategic use of nitrogenous fertilisers in the colder regions for winter, early spring and late autumn grass growth.

Animals are now farmed outside all year round in climates similar to those in large parts of North America and Europe.

And as subsidised farming in those countries becomes unsustainable, many farmers are turning back to low-input management methods.

The first step is to "open the gate" and let the animals harvest most of their own feed requirements from good quality pasture, for the months of the year in which that pasture is growing.

In Northern Hemisphere climates where snow and frost do shut down outdoor farming activities in the winter months, New Zealand pastoral farming techniques can still be used to cut costs and make agriculture more sustainable.

It has been estimated that the energy requirements per unit of protein in New Zealand pastoral production are only half to one third of those in the United Kingdom and Europe.

Out of the thousands of grass, legume and herbs species found growing in natural grasslands, few have been found suitable for managed farming systems.

Given the importance to the national economy the discovery of the suitable varieties and subsequent utilisation of pasture-only systems for farm livestock in New Zealand has been called the "Grassland Revolution".

Originally the pioneers replaced the native scrub cover with low-producing grasses such as cocksfoot, timothy, fescues, bluegrass, dogstail and browntop which would survive in the poor soil fertility. But on these pastures it was not possible to run more than one sheep to the acre and perhaps a few house cows.

When the call came to lift production for export, and refrigerated shipping made that possible, farmers either had to extend their pastoral boundaries or increase productivity per acre. In the North Island, large new tracts of land were not available, and Maori tribes stoutly defended new European incursions.

The answer was found in new perennial ryegrass and clover cultivars bred by scientists and affordable sources of phosphatic fertilisers. For most of the past 100 years New Zealand has led the world in combining grasses and legumes in the same sward, in a symbiotic relationship which greatly benefits the grazing animals. Latterly, different improved grasses, legumes, grazing herbs and even forage brassicas have been bred or imported, then trialled and introduced to New Zealand farmers. These are sown in more complex mixtures to extend seasonal growth, help minimise weed invasion, provide more energy and a more varied diet.

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RYEGRASS

Perennial ryegrass (Lolium perenne) is the most dominant temperate grass in New Zealand because it grows well in a variety of average-to-good soil fertilities, is easy to establish, and forms compatible mixtures with white clover and several other pasture species.

It also tolerates intensive grazing, establishes rapidly and has a high level of persistence. Some pastures will last 50 years in conditions of regular rainfall and no extreme summer and winter temperatures.

New Zealand soils are naturally low in phosphate (P) and nitrogen (N). To lift the phosphate levels, superphosphate fertiliser and its blends are widely used, spread by trucks or by air. Most farmers also add potash (K) and sulphur (S) sources, and correct any mineral deficiencies which might arise in the livestock.

To grow quickly, grasses require ample nitrogen. This can often be a limiting factor when soils are wet and/or cold because microbes are limited in their ability to decompose litter and release the nitrogen. As dairying and more intensive beef and lamb production moves into colder regions of New Zealand, such as Southland, the availability of cost-effective nitrogenous fertiliser, both imported and from New Zealand's own petrochemicals, has extended the grass growing season and the boundaries of "all-grass wintering".

But the most economic way of ensuring that grasses have enough nitrogen to grow is to establish legumes, mainly clovers, in the same sward. 

Another way to extend the growing season is to use annual or short-rotation ryegrasses, usually Italian (Lolium multiflorum) or hybrid ryegrasses. Italian and hybrid ryegrasses, both annual and near perennials, grow more in winter and early spring and have a higher digestibility for animals. It is this combination that makes these grasses effective as a winter crop between cereal crops, but also on dairy farms and in other animal systems where animal performance is a higher priority than persistence.

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WHITE CLOVER

White clover (Trifolium repens) is a productive and persistent legume found in most New Zealand pastures. It supplies nitrogen for grass growth via its nitrogen fixation, produces high quality feed and provides useful seasonal production, particularly in summer. The proportion of white clover in well-managed, fertile pastures can go up to 20-30%, but it can go as low as 2% in infertile hill country pastures. White clover establishes well from seed and spreads readily through pastures via stolons, and can regenerate after treading damage or pest attack.

Winter growth of white clover (at 8-9OC or less) is low and it is at its best during spring and autumn. During hot, dry summers its leaves die back, but the plant re-grows from the stolons.

The process of biological nitrogen "fixation" from the air by legumes like white clover, so that nitrates are subsequently available to associated grasses and herbs, is calculated to be worth hundreds of millions of dollars annually to New Zealand farmers, and ultimately the country. As mush as 350kg N/ha/year can be fixed depending on the percentage of clover in the pasture and its growth rate.

It has been estimated that if all 10 million hectares of New Zealand grassland contained 20% clover, then some 2 million tonnes of atmospheric nitrogen would be fixed into the soil/pasture/animal system each year. 

Legumes only fix nitrogen when they form an effective symbiotic relationship with Rhizobium bacteria, which live in nodules on the roots of the clover plants, capture atmospheric nitrogen and convert it into ammonium ions and amino compounds.

Rhizobia do occur naturally in soil, but often the right types are attached to the clover seeds by coating before sowing.

Nitrogen fixation by clover and the rhizobia can be suppressed by providing nitrogenous compounds for plant growth via fertiliser.

In the pastures of many Northern Hemisphere countries, clover is not encouraged, because nitrogenous fertilisers are readily available, and therefore the benefits of nitrogen fixation are not gained. New Zealand farmers get very low cost nitrogen by including the legumes in their pastures.

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ALL-GRASS WINTERING

When the seasonality of pasture production does not match animal requirements, then options for manipulating the environment (e.g. irrigation, fertiliser), altering pasture supply through grazing management, feeding supplements (e.g. silage, hay) or growing species with a different seasonal distribution need to be considered.

Most livestock farms in New Zealand, throughout the whole country, use to a greater or lesser extent feed conservation methods which harvest surplus pasture in spring, store it to prevent deterioration in energy and nutritional values, and feed it out during the winter, and at times of adverse weather events, like droughts, snowfalls and floods.

Because the livestock stay outdoors on the paddocks 365 days of the year, this is often called "all-grass wintering".

The feed conservation methods n ow including hay making, pit silage, haylage and bailage, using plastic bags and wraps to prevent aerobic bacteria spoiling the feed.

Farmers use feed plans and budgets to ensure that animals have enough to eat and to plan their fodder conservation and feed-out programmes. However, because of the high relative cost of grain and processed feeds, supplementing with these is not usually an option for adult stock, even when cows are continuing in lactation.

Variations in calving and lambing dates, and the use of "run-offs" during winter to take some or the entire cow herd, are also used to balance the feed supply and demand on the home farm. Often winter crops are grown, such as brassicas, to supplement the standing and conserved pastures.

The right combinations of stocking rates and movements, genetics, pasture species and fodder conservation techniques can provide for "all-grass wintering" in some quite hostile climates, such as found in Otago and Southland.

The breakthrough in all-grass wintering for dairying in colder climates came from longer rotation lengths (50 to 100 days) and the need for longer-term feed budgeting, monthly pasture growth monitoring in every paddock and the systematic approach to feed planning for the whole farm.

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INTENSIVE PASTURE UTILISATION WITH SUBDIVISION

A key technique for managing pastures, controlling access to pastures by livestock and lifting the overall productivity of pastoral farming is to employ closer subdivision, either with permanent or temporary fencing.

The significant gains in animal production per hectare over the past 40 years in the New Zealand dairy industry have been achieved largely through improved grazing strategies allowing more of the herbage grown to be harvested, as well as through improved animal performance through breeding.

Rotation lengths and power fencing for strip or break feeding are the key management tools, with or without supplementary crops for standing feed such as chou molier, swedes, greenfeed cereals, brassicas or annual ryegrasses.

In winter carefully conserved "banks" of feed are apportioned out to livestock on a daily basis, by moving the animals into new paddocks and/or "breaking" those paddocks up with temporary power fences. This is in contrast to employing the same stocking rate across the whole farm and "set stocking" over the winter months, i.e. a fixed number of animals left alone on the same paddock. Pasture utilisation is lower and plant recovery times can be longer.

Intensification is also used during high pasture and crop growth periods to lift the numbers of animals which can be "finished" more quickly for slaughter.

Pasture varieties, fodder crops, techniques and products have all been developed in New Zealand for lifting the productivity of pastoral agriculture. These are now sold and taught around the world.

SOURCES:
Grasslands of New Zealand, by B.H. Levy.
The Grasslands Revolution in New Zealand, by P.W. Smallfield.
Pastures, their ecology and management, edited by R.H.M. Langer, published by Oxford University Press.
New Zealand Pasture and Crop Science, edited by James White and John Hodgson, published by Oxford University Press.
Pasture and Forage Plants for New Zealand, by Deric Charlton and Alan Stewart, published by New Zealand Grassland Association and Grassland Memorial Trust.