From the earliest times, pastures have formed a most important part of agriculture. They are the principal source of livestock feed, they help build soil fertility on which much crop production depends, and they are important in protecting soil against erosion.
Pastures are usually a major feature of small farms and knowing how to manage them is a key to success.
At first, many people think of pastures in terms of grasses. But it is most important to understand that they also include many legumes such as clovers and lucerne. Pasture productivity would be extremely low without legumes to act as a source of nitrogen for the grasses and as a source of high quality herbage for the grazing animal.
Climate:
The grasses and legumes which constitute the world’s pastures have been adapted to an immense range of climates and soils. Even within New South Wales our common grasses and legumes represent a great range of adaptation, with only a few being adapted to any one location.
This results, for example, in major differences between the pastures of the north coast, the central tablelands and the south-west slopes.
The main determinants of climate include rainfall, temperature, and what time of the year rainfall occurs. The following indicate the main trends.
- Average annual rainfall in the State diminishes very strongly westwards with the isohyets (lines joining places of equal rainfall) running north-south.
- Temperatures are altered by distance from the sea. Thus, the equable maritime climate of the coast gives way to the continental climate inland with colder winters and hotter summers. Altitude is another major effect on temperature and precipitation, with the coldest climates in the State at high altitudes on the tablelands.
- The south of the State has a Mediterranean-type climate with rainfall occurring from autumn to spring. The rainfall becomes summer dominant northwards from a transition zone over the central areas of the State.
Different grasses and legumes are needed for the conditions which arise from the combinations of these changing climatic factors. Thus, for example, while annual legumes like subterranean clover are well adapted to the southern slopes, growing well from autumn to spring and remaining dormant during the dry summer months, the perennial legume, lucerne, is specially well adapted to northern areas making most growth during spring to autumn and responding well to summer rainfalls.
Soils:
The wide variation in climate is matched by the variation in soils. Knowing the type of soils on your property is vitally important, not only in determining what grasses and legumes can be grown, but in assessing how productive they are likely to be. When you take into account the tendency to allocate non-prime land for small farms, soil fertility is a basic consideration. Soils are also related to fertilizer requirements and whether special measures such as liming might be needed to remedy soil acidity.
Nearly all soils in the State are, to a varying extent, deficient in phosphorus (P) in their natural state. The P status of any particular soil at a given time depends on the natural fertility, how much phosphate fertilizer has previously been applied, and when the last applications were given. A question that must be faced by all producers is how much will be needed to build up fertility to an acceptable level and then maintain that level.
Sulphur (S) is often deficient too, but the needs for S and P can usually be met at the same time by using superphosphate fertilizers which supply both nutrients. Potassium (K) usually does not become deficient until an area has been heavily exploited for agricultural production over a period of years and much K has been taken by plants and removed from the site in the produce, for example, after heavy hay crops have been taken off an area for several years. Where it is established that a K deficiency exists, the need is met by using muriate of potash fertilizer either alone or in combination with phosphate fertilizers.
The most deficient major nutrient is nitrogen (N). This need is met, not through fertilizers, but by the inclusion of a good component of legumes in pastures. This matter is referred to in more detail later.
There are a number of minor elements which are sometimes required of which the most important is molybdenum (Mo). The need for Mo is usually met by applying superphosphate which has had Mo added to it (Mo super) every three to five years.
Soil acidity:
Many soils in the State are acid and soil acidity is an increasing problem which is likely to confront many people on small farms. This is perhaps especially likely where small farms have been established on recently cleared land on the tablelands. These areas tend to consist of light sandy soils which are naturally quite acid and become increasingly so after a number of years in improved pastures.
These areas require tolerant pastures species and the use of lime to lower acidity in order to achieve a moderate level of production, but in fact, many such areas should not have been cleared in the first place.
Pasture management:
Pastures are often thought of as being an extensive type of agriculture compared with cropping, with little input and relatively low production. But, under management for high production with the use of improved pasture species and adequate levels of fertilizer, grassland farming can be as intensive as any other form of agriculture.
One of the chief points in referring to the complexity underlying pastures, arising from climate, soils, species of pasture plants, fertilizers and management options, is to highlight the importance of local knowledge for making a success of your pastures. Pasture management is very complex, but you can develop an adequate working knowledge for your area without having a wide understanding of all the intricate relationships involved.
It is important to get advice from those who have a sound understanding of local conditions. Seek advice from locally based advisers and also, of course, look over the fence at what successful neighbours are doing.
Selecting Pasture Species:
Selecting a pasture mixture which will be more productive than the typical natural pasture on your property will be much easier for you if you learn what you can about the local climate, the characteristics of your soil, the pasture species available and the animals which will be grazing the pasture.
The most important factors to consider are the rainfall and temperature patterns, soil texture, soil fertility, and seedling vigour. Other factors of i mportance are the resistance of the pasture species to insect pests and diseases and the needs of your animals at various times of the year.
Rainfall distribution:
A winter rainfall area typical of southern New South Wales favours perennial, drought tolerant grasses such as phalaris and cocksfoot, and short-term annual species such as Wimmera ryegrass and subterranean clover.
The summer rainfall of northern New South Wales favours perennial,summer-growing grasses such as kikuyu, paspalum, buffel grass, setaria and Rhodes grass and perennial legume species such as lucerne and white clover.
Temperature:
Typical of the grasses which thrive in high temperature are the paspalum and kikuyu pastures of the north coast which produce their greatest bulk of feed in the peak of summer. Adequate summer rainfall is essential for perennial summer-growing pastures because high temperatures mean high water use by plants.
Very few pasture species grow during tile cold of mid winter. Short days also play a part in restricting growth in the wintertime. However, the ryegrasses and white clover, for example, are capable of fair growth in late autumn and early spring. One type of white clover, Haifa, can make good growth in colder weather when compared with other types of white clover.
Soil texture:
Soil texture is a term relating to the proportion of sand, silt and clay in a soil. A soil with a high proportion of sand or silt is referred to as a light soil. On the other hand, a heavy soil is one with a high proportion of clay particles.
Other factors being equal, a light textured soil is a better drained soil than a heavy textured soil. Some pasture species have a preference for soils of a particular texture. For example, Demeter fescue, strawberry clover, reed canary grass and Trikkala subterranean clover are well suited to heavy soils.
Most other pasture species prefer lighter textured soils. At the extreme is Serradella which does best on very sandy, well-drained soils.
Soil fertility:
Soils with high levels of the nutrients necessary for plant growth are very fertile soils. At the other end of the scale are poor soils which have very low levels of the essential nutrients. The use of fertilizers will improve the fertility of a soil. You will find that, as fertility builds up, better quality species such as white clover will spread and persist.
The level of nutrients available greatly affects the performance of pasture species. Much of the land subdivided into small holdings in recent years is of low fertility. There are species such as subterranean clover, Wimmera ryegrass, Serradella and Namoi Woolly Pod vetch which will persist in relatively low soil fertility. Perennial ryegrasses, phalaris, kikuyu, white clover and red clover are species suited to higher fertility soils.
Soil pH:
The reaction of a soil to a relatively simple test called a pH test will give you a measure of its acidity. On the pH scale, a reading of 7 is “neutral”. A figure below 7 indicates an acid soil while a reading above 7 indicates an alkaline soil.
Most pasture species do best on slightly acid soils of the range 6.0 to 6.5 on the pH scale. Subterranean clover will tolerate moderately acid soils below this level while lucerne prefers a neutral to slightly alkaline soil. The application of lime will lower the level of acidity (raise the pH reading) of a soil. Normally, it is not necessary to have a pH test done on your soil but if you are in doubt check with the Department of Agriculture or representative of a fertilizer company.
If white clover is growing naturally on your soil, the chances are that you will not have to worry about a pH test. If, however, you decide to have a soil test done to check the level of other elements, you will find that a pH test is carried out as a matter of course.
Other considerations:
Where possible, select species that are resistant to pests and diseases of local significance. New lucerne varieties now available, for example, have been developed for resistance to spotted alfalfa aphid and phytophthora root rot. Pasture species vary in their seedling vigour or ability to become established in competition with other species or weed growth. Be careful in choosing the grass components of the mixture in particular. Phalaris, for example, can easily be dominated by annual ryegrasses and fail to establish satisfactorily.
In selecting a pasture mixture it is important to have a balance of legumes and grasses. The legumes such as white clover, besides being very nutritious, have the ability to use nitrogen from the air which in turn, makes the grasses grow better. On the other hand, a dominance of legumes can cause bloat in cattle, a condition where the stomach is distended by gases fermented following the grazing of legumes.
The accompanying table will help you select a suitable combination of species. For details on sowing rates and fertilizers seek advice from the local district agronomist of the Department of Agriculture.
Pasture Establishment:
Most grasses and pasture legumes native to Australia are not very productive. They have a short growing season, do not produce a bulk of feed, and are of poorer quality than many introduced species. Some introduced grasses such as carpet grass in coastal areas of New South Wales, and legumes such as white clover, have become naturalized and spread where conditions suit them.
The pastures on most small farm subdivisions are not capable of fattening stock. The carrying capacity of these natural pastures is about ten adult sheep or one cow or one horse to 5 ha. It is possible for you to double the stocking rate of your natural pastures by introducing improved species of grasses and legumes and using recommended fertilizers. In general terms, topdressing with fertilizer, particularly superphosphate, will increase the productivity or carrying capacity of existing pastures. Seek local advice on pasture species occurring naturally and on the way they are managed.
If you want to have really productive pastures over a longer period of the year, you should consider establishing the most productive grasses and legumes suited to your district.
Preparing a seedbed:
The aim of preparing a seedbed is to reduce weed competition, conserve moisture and allow good contact between the soil and the seed at sowing. Satisfactory seedbeds can be prepared with a wide range of cultivation equipment. Be guided by local farmers and advisory officers of the Department of Agriculture before you make any purchases but remember that it may be in your best interests to hire a contractor to do the work.
A typical program for autumn sown species in inland areas would be to plough in September while the ground is soft, graze hard through summer, cultivate with a plough or scarifier in March and continue cultivation with scarifier or a harrow when weed control is needed. This allows plenty of time for the initial ground cover to rot away. Sow, when conditions are suitable, from mid April to June. The cultivation produces a fine, firm seedbed. For spring sown species allow three to four months preparation if possible.
In coastal districts where rainfall is higher, the length of time between first ploughing and sowing in the autumn can be reduced to about two months but the objective should still be to produce a clean, fine and firm seedbed.
Much shorter preparation can still result in good establishment, and is indeed advisable, if soil erosion is a risk. For quick preparation, graze existing ground cover hard up to sowing rains, cultivate twice with an offset disc harrow for example, and increase the sowing rate by about 25 per cent.
Sowing:
Many implements are available to sow the seed. Special pasture seed and fertilizer box attachments behind cultivating implements complete the job in one operation. Seed can also be mixed with fertilizer and sown through a fertilizer spreader. If this is done, legume seed should be lime pelleted and the seed and fertilizer not left in contact for more than one day. For small areas the seed can be broadcast by hand.
The seed should be lightly harrowed after sowing but make sure it is not covered by more than about 20 mm of soil. A light roller used after harrowing can improve the germination by up to 50 per cent by bringing the seed into better contact with the soil.
Surface sowing:
Pastures can be established by dropping seed straight onto existing pasture without disturbing the soil in any way, provided the ground cover is not too dense. On large areas seed can be sown economically from aircraft. Surface sown pastures will establish better if the existing pasture is heavily grazed before sowing. Some unwanted species can be killed off by applying herbicides before sowing but you should seek advice beforehand.
When sowing direct onto the surface, increase the sowing rate by at least 50 per cent. Under less than ideal conditions there are advantages in sowing half the seed on the full area and waiting a month before sowing the other half of the seed.
Sod seeding:
Sowing direct into the soil under existing pasture is called sod seeding. There are special implements available using either tynes or discs to penetrate the soil to allow the seed and fertilizer to come in contact with the soil. Sod seeding is particularly suitable in rough, erosion-prone country.
The usefulness of existing summer-growing natural pastures can be extended by sod seeding winter-growing species such as subterranean clover or vetch in the autumn. Perennial species such as lucerne and phalaris are difficult to establish by sod seeding.
Companion or cover crops:
Pastures are best sown alone but they can be established with a companion crop such as wheat or oats. The companion crop may give you some early grazing but it does compete with the pasture for light, nutrients and moisture.
If a winter cereal such as oats is used as a cover crop, its seeding rate should not exceed 25 kg per ha and should not be sown until there is little danger of the top soil drying out. Use cattle for preference to graze the cover crop and graze lightly to prevent damage to the underlying pasture. Remove stock immediately after rain to prevent bogging down of the pasture and crop.
Grazing:
Graze lightly in the first year to allow good establishment and good seed set of annual species. Don’t graze too early. If plants can be pulled out of the ground by hand, delay grazing until they are more firmly established.
Recommendations:
Sowing rates and fertilizer recommendations are available for each district from Department of Agriculture and local seed and produce suppliers.
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