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PASTURE IMPROVEMENT

Pastures are either native or improved, and provide grazing animals with nutrition. Winter time is the most critical period for pasture because even where the rainfall is adequate, low temperatures will slow pasture growth. Depending on the stocking rates, winter fodder crops such as wheat, oats, and barley are also part of the pasture system.

Farmers are conscious of the "feed year" concept and whether their approach is scientific or not, an estimate of carrying capacity has to be made for the various seasons of the year. For example, the maximum demand for fodder supply for calves occurs after they are about 6 weeks old. Feeding cattle on stored fodder should be avoided wherever possible, because it is necessary at that time of year when feed demands are high and so therefore, is the cost. At certain periods of the year there may be adequate supplies of dry grass but a deficiency of protein. In this situation it is feasible to supply molasses and urea mixtures.


PASTURE TYPES
 
A large variety of pasture types are grown but only in northern NSW are some of the tropical legumes such as desmodium found. Lucerne, red clover, white clover, and subterranean clover are widely used. A large variety of grasses are available, the choice depending on the suitability of the plant to soil, climate conditions, and the need to provide feed throughout the year. Buffel grass, kikuyu, paspalum, phalaris, rye grass, and cocksfoot are found in the major grazing areas.


DIAGRAM 1 ILLUSTRATION OF A LEGUME PLANT SHOWING THE NODULES OF NITROGEN FIXING BACTERIA.


To provide a greater amount of feed during winter; wheat, oats, barley, turnips or rape may be grown. Summer fodder crops are found in northern NSW and usually one of the forage sorghums is grown. Beef cattle farmers expect in drought time or even during normal winters to supplement slow pasture growth with lucerne hay, pasture hay, cereal hay, silage, and grain oats in storage.


PASTURE SPECIES

The farmer has to consider the suitability of pasture species for the subject area as no one plant makes a satisfactory all year pasture. Pasture grasses use nitrogen from the soil whereas legumes replenish soil nitrogen. Therefore, the farmer has to consider pasture mixes and probably a combination of paddocks with some with a predominance of summer growing pasture plants and some with a predominance of winter growing pasture plants and still other paddocks for summer or winter growing fodder crops. For Australia, a generalized overview of the most common pasture plants are as follows:


1. TROPICAL PASTURE PLANTS
* Townsville lucerne - stylosanthes sundaica
* Phasey bean
* Paspalum - paspalum dilatatum
* Buffel grass - cenchras ciliaris


2. TEMPERATE PASTURE PLANTS

* Subterranean clover - trifolium subterranean
* Lucerne - medicago sativa (alfalfa)
* Perennial ryegrass - lolium perenne
* Cocksfoot - dactylis glomerata


DIAGRAM 2 A GENERAL DISTRIBUTION OF AUSTRALIAN PASTURE PLANTS




See pasture improvement in NSW


TEMPERATE PASTURE SPECIES

The following are general comments on the important characteristics and adaptation of the main species of temperate pasture species:


MAJOR LEGUMES


ANNUAL MEDICS
Annual medics are winter growing legumes which regenerate each year from seed. They are best suited to the neutral to alkaline soils and in NSW are limited to the lower rainfall areas of the wheatbelt and westwards. The most useful species is generally regarded as being BARREL MEDIC (medicago truncatula). SNAIL MEDIC (m scutellata) has high insect resistance but is generally less persistent than barrel medic. There are several naturalised species including BURR MEDIC (m polymorpha), WOOLLY BURR MEDIC (m minima), CUTLEAF MEDIC (m iaciniata) and SPOTTED BURR MEDIC (m arabica) that are also useful in some situations.


CLOVERS
SUBTERRANEAN CLOVER (trifolium subterranean):
A winter growing annual suited to acid to neutral soils which is the basic component of pastures in southern and central NSW. In the northern half of the State, rainfall requirements for each variety need to be increased by 50mm. All varieties of sub clover recommended in NSW are low in formonotin, the plant oestrogen which causes clover infertility disease in sheep.


WHITE CLOVER (trifolium repens):
A perennial species suited for areas above 700 mm rainfall or where irrigation is available. Grows on a wide range of soils. Its main growing period is spring, Summer and autumn.


RED CLOVER (trifolium pratense):
Red clover is a short lived summer growing perennial. best suited to the central and south coast and tablelands with over 650mm reliable rainfall.
MAJOR GRASSES

COCKSFOOT (dactylis glomerata):
A perennial which needs well drained soils. It has a lower nutritive value than ryegrass and tall fescue but is one of the better perennial grasses on less fertile acid soils. Susceptible to scarab and oncopera damage.


PHALARIS ( phalaris aquatica):
A widely adapted perennial grass which forms a stable pasture under heavy continuous grazing, drought and insect attack. A highly productive grass with most growth from late autumn to spring, but tends to be summer dormant. It needs to be grazed heavily in late spring and autumn to maintain its nutritive value and encourage clover. Best suited to tablelands and slopes but performs well under irrigation. It is a preferred replacement species in weedy situations and is useful for soil conservation. It occasionally causes a condition known as "phalaris staggers", especially in sheep. Generally requires 50mm extra rainfall for satisfactory growth in the northern half of NSW. It is sensitive to high aluminium levels.


PERENNIAL RYEGRASS (lolium perenne):
A perennial pasture species suited to areas where summers are cool and the rainfall evenly distributed. It is a nutritious grass requiring fertile soil. Perennial ryegrass swards are rapidly thinned by drought especially under heavy grazing. Its main growth is in autumn and spring and it is easy to establish. It rarely persists for longer than 2 years on the north coast.


ANNUAL RYEGRASS WIMMERA (lolium rigidum):
A self regenerating annual which is regarded as a weed in cropping areas. It is a vigorous grass giving good winter and spring production, and is moderately salt tolerant. It becomes more fibrous towards maturity than other annual ryegrasses.


TALL FESCUE (festuca arundinacea):
A perennial pasture grass suited to the following locations:

Can be grown successfully in wet situations at lower rainfall. Requires reliable summer rainfall or irrigation to be persistent. It is relatively slow to establish but quicker ground cover is achieved with high seeding rates and provides good year round production of quality feed. It tolerates waterlogging and both acid and alkaline soils.


PASTURE IMPROVEMENT
 
Pasture growth is vigorous on the better class soils and on irrigated farms and heavier stocking rates can be carried throughout the year. Therefore, irrigated lands show a substantial increase in value compared with otherwise comparable lands. For example, in the Hunter Valley. Three factors have allowed the rapid growth of pasture improvement to occur: The ideal pasture improvement program is the growing together of grasses and legumes. This is because grasses provide bulk and carbohydrates and legumes supply large amounts of protein. Pasture improvement is the improvement of natural pasture by sowing seeds of selected strains of legumes or grasses combined with fertilizer application. Sowing and top dressing alone is insufficient to establish a good pasture. Also required are:

EFFECT OF CLIMATE AND SOILS
 
The distribution of sown pastures in Australia is limited by various climatic factors. Rainfall, temperature, and seasonal variation in the length of daylight are of particular importance. The map attached indicates that generally, the 300mm isohyet in Queensland and the 762mm isohyet in the Northern Territory and the northern Western Australia are the limits for pasture improvement. This broad picture is modified considerably in different localities according to the evaporation rate, the reliability and distribution of rainfall, and a combination of other environmental factors.

On the tablelands periods of adequate water for plant growth alternate with dry periods. Diagram 3 shows the average rainfall at Armidale with the amounts necessary to keep plants supplied with water.


DIAGRAM 3



EFFECT OF TEMPERATURE
 
Low temperatures restrict growth in winter in the most southerly parts of the continent and in the high country along the eastern seaboard. The frequency and intensity of frost sets a limit on the distribution of many species, especially the summer growing ones. At the other extreme, high summer temperatures even where there is abundant rainfall will prevent the survival of many species of temperate origin.


LENGTH OF DAYLIGHT

The length of daylight at different times of the year is a critical factor in the initiation of flowering of many plants and hence of the setting of seed and ultimate survival. The variation which occurs with latitude determines the limits within which some of these may be grown. Plant breeding, plant introduction and widespread pasture trials are continually providing new information adapted to the more difficult climatic conditions and therefore, are extending the boundaries of sown pastures.


SOIL DEFICIENCIES
 
Soil deficiencies limit the distribution of improved pasture but research has identified the lack of the essential nutrients to replace those lost in the natural soil.


LACK OF PHOSPHOROUS
 
The phosphate level of the soil is of vital importance for pasture growth and replacement is an important farm management decision. The final decision is subject to questions of equity, taxation, and opportunity cost. Most soils in Australia are deficient in phosphorus and where there is sufficient rainfall to maintain an adequate response the application of superphosphate is necessary to increase output.

Topdressing native pastures is also practised and usually achieves greater yields of herbage as well as improvements in quality from greater growth of naturally occurring legumes which it promotes. However, the maximum benefit of fertilizer application can only be achieved in association with introduced pasture species with their greater capacity for bulky and high quality production. For these species a reasonably high soil phosphorus status is essential for both establishment and growth.
LACK OF NITROGEN
 
Australian soils are also characteristically deficient in nitrogen. In the absence of a cheap industrial source of this element for application as a fertilizer such as occurs in some overseas countries the Australian farmer is heavily dependent on legumes to provide for the needs of his pastures. Except on irrigated land and for certain special purposes such as the provision of an early "bite" in spring, sulphate of ammonia, urea, and other nitrogenous compounds are rarely used.


LACK OF OTHER ELEMENTS
 
Pasture research has also shown a marked response to the application of other major plant nutrients such as sulphur, calcium, potassium, and magnesium. Deficiencies of these elements are not nearly so widespread as those of phosphorous and nitrogen but in certain localities can be more important. The extent of the areas in which they are limiting production is not yet fully known and as is the case with potassium may be increasing under current systems of land use. In circumstances where heavy demands are being made on the potassium reserves in the soil such as is the case when hay is sold off the farm, those reserves may become exhausted and thereafter require replenishing every few years.


LACK OF MINOR TRACE ELEMENTS
 
The most dramatic evidence of how far deficiencies of plant nutrients may limit production lies in the work done with the minor or trace elements such as molybdenum, zinc, copper, and boron. A few kilogram per hectare of the appropriate compound applied to a soil lacking the element will satisfy the requirements of pastures for years and will often make the difference between a complete failure and a highly productive pasture.


EXAMPLE
 
The development of the Ninety Mile desert now known as Coonalpyn Downs in South Australia is an outstanding example or replacing the trace elements of copper and zinc.

It is not always possible simply to detect a deficiency of a certain element and correct it with the right dose of fertilizer. If the element is present n a form in which the plant cannot readily absorb extra applications of the fertilizer are required. For example, although the basaltic red loams of the north coast of NSW have a high natural phosphorous content, once deficiencies of certain other elements have ben corrected pronounced response can be obtained by additional dressings of superphosphate.


TYPES OF FERTILIZER
 
Below is the chemical breakup of the common types of fetilizer used in Australia for pasture sowing and maintenance. The rate of application varies greatly with soil fertility and land use. A soil test should be used along with paddock history to determine the specific application rate. The products market * are those generally used for sowing and the remainder are used for pasture maintenance. Single superphosphate is used for both pasture establishment and maintenance:


TABLE 1 FERTILIZER ELEMENTAL ANALYSIS







RESPONSE
 
The response of pasture to fertilizers is greatly affected by climate, the general characteristics of the soil, the type of stock grazing, the farmer's system of grazing management, and the varying demands of the component pasture species. It is therefore, very difficult to determine the optimum amount of fertilizer application for any one farm without conducting trials. Fertilizer responses are not even necessarily caused by the particular constituent elements for which they are purchased. For example, the responses to super which have been traced to the sulphate content of the fertilizer instead of the phosphate or the response to lime which was traced to the molybdenum released from reserves in the soil as a result of the application rather than directly due to the lime itself.
Pasture growth is vigorous on the better class soils and with irrigation. In these areas high stocking rates can be maintained year round. This is the main reason why irrigated lands show a dramatic increase in value compared with comparable non irrigated lands. For example, in the Hunter Valley of NSW and the Berri in South Australia.


pH FACTORS
 
The acidity or alkalinity of the soil is also an important influence on the type of pasture which may be grown and on the soil microorganisms associated with plant growth. The soil reaction is expressed in terms of the pH scale.
The pH scale measures the hydrogen ion concentration in the soil. The value pH7, represents neutrality while the lower values are acid and the higher are alkaline. The degree of tolerance to different pH levels varies widely amongst species. The bacteria associated with legumes of the temperate regions such as clovers and medics are particularly susceptible to acidity.

On acid soils and whenever these legumes are sown in contact with super, appropriate precautions are necessary to protect the bacterial culture such as the sowing of lime pelleted seed, or the use of neutralized super. Tropical legumes and their associated rhizobia appear to be tolerant of much more acid conditions. Lower calcium levels and in general do not require additions of lime.
The required pH levels for a number of plants are shown in the table below:


TABLE 2 PH LEVELS REQUIRED BY A NUMBER OF PLANTS




PHASES OF PASTURE IMPROVEMENT
 
The objectives of pasture improvement usually include reaching a high level of production with grass and legumes growing in a balanced sward. The more vigorous grass uses the surplus nitrogen produced by the equally vigorous clover. To reach this phase the pasture passes through a number of stages - see diagram 6. The aim is to reach the objective as efficiently and quickly as possible. That is, to bridge the soil fertility gap between a native pasture and a highly productive perennial grass/legume pasture.


DIAGRAM 6 THE PHASES OF PASTURE IMPROVEMENT




PASTURE APPLICATION

RADICAL
 
Old pasture is ploughed up, cultivated free of weeds, and the seed sown with a combine into a clean seed bed. This is the most costly method but leads to better results and up to 70% of the seeds will germinate and grow. The radical method also preserves soil moisture, reduces competition, releases nutrients such as nitrates which benefit young plants, and requires less seed.


SUBSURFACE SOWING
 
A method of drilling pasture seeds into an existing pasture and up to 20% of the seeds may germinate. Grass seeds sown this way cannot compete against native grasses but are more successful with legumes. Sub clover and white clover can be established readily this way. New technology in seed preparation and sowing has resulted in a high success rate.

TYPICAL METHODS USED ARE SHOWN IN DIAGRAMS 7 AND 8.
 
DIAGRAM 7: PLACING A FERTILIZER BAND CLOSE TO THE SEED IS IMPORTANT FOR GOOD ESTABLISHMENT.




DIAGRAM 8: THE TYPE OF SLOT INTO WHICH THE SEED AND FERTILIZER ARE PLACED BY VARIOUS MACHINES.



TABLE 3: SHOWS THE ADVANTAGES AND DISADVANTAGES OF DIFFERENT METHODS OF     APPLICATION



See air seed and super (ass)


BENEFITS OF PASTURE IMPROVEMENT
'
The establishment of pasture improvement has a number of important effects on farming. These are:


INCREASE IN CARRYING CAPACITY
 
For example, on the New England tablelands where areas which before could only carry 2 wethers/ha now carries 8/10 breeding ewes/ha. One property on the southern Tablelands has been carrying up to 25 sheep/ ha with careful management.
RISE IN SOIL FERTILITY
 
If the pasture improved land is ploughed up and wheat planted the wheat crop will grow much better than in an ordinary paddock. If stock are grazed alternately on improved and native pastures the animals will collect nutrients from the good pasture and transfer them to the native pastures via their droppings.


CONSERVATION OF FODDER
 
The production of plant material from improved pasture may be so great that in some seasons that much of the fodder can be conserved.


CHANGE OF LAND USE
 
Pasture improvement may raise the productivity of poor land to such an extent that the agricultural land use changes entirely. For example, from fine wool to sheep breeding on the New England tablelands.


DIAGRAM 9: APPROXIMATE STOCKING RATES FOR DIFFERENT LAND TYPES WITH INCREASING DEVELOPMENT




See pastures, grasses and legumes in Queensland


COSTS OF PASTURE IMPROVEMENT

There are other costs besides the cost of purchase and application of the pasture and fertilizer. These include the marginal costs of:

DISEASES
 
The more intensive land use and new pasture expose the stock to new diseases and pests. For example, legumes such as subterranean clover, contain substances similar to sex hormones which may affect the fertility of ewes grazing on them. Wethers may develop proshitis and cattle; bloat. However, generally, the many advantages from pasture improvement far outweigh problems such as these.


ACIDIC SOILS
 
The large expansion and intensive application of superphosphate since World War 2 has caused a gradually buildup of soil acidity and in many parts of Australia this has reached critical levels. The problem can be mitigated by the application of limestone and/or the planting of acid tolerant plants.
















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