sustainable agriculture

SUSTAINABLE AGRICULTURE

The above measures of performance are useful financial analyses. However, maximising profit may not be the best solution particularly in the short run, but rather, the farmer should look at sustainable agriculture over the long run. It is possible to exploit the inherent features and fertility of agricultural land so as to enjoy large short run profits, for example, by overgrazing. However, if the farmer does this he/she will lose in the long run because the property will suffer damage such as soil erosion which will reduce gross margins over the long run.

Sustainable agriculture is agriculture which maximises profit over the long run. That is, agriculture which preserves the soil's structure and fertility etc so that the farmer enjoys year in year out profits and the farm is no worse off after farming than it was before. Such farm management or good husbandry will preserve the land asset.

The increasing concern about the long term condition of the land and the pressure to get more and more from it makes this one of the most important questions that farmers can ask. The answer lies in using the land within its capability. In other words, using the land without causing permanent damage or a reduction in its future productivity.

THE PROBLEM

To ensure that the farm system is used within its capability, farmers must overcome several problems:

Water erosion
Decline of organic matter in the soil and breakdown of soil structure
Wind erosion
Decline in native vegetation
Dryland salinity.

Proven solutions to these problems exist and many farmers have put them into practice. The following are not an exhaustive list of sustainable measures but rather, the more common and important ones. The following are the most common farming techniques used in sustainable farming.

SUSTAINABLE METHOD 1 - CONTROL RUNOFF

Run off from rainfall can be effectively controlled and erosion reduced by properly constructed and maintained contour banks, waterways and diversion banks. The value of structures to control run off has been proved on farms in the northern agricultural district for over 50 years. Most often a combination of structures is required to control the flow of runoff across cultivated land so that:

erosion is minimised
flooding is prevented
waterlogging is minimised.

SYSTEMS FOR THE CONTROL OF RUNOFF

The design of systems to control runoff should be planned well because fences, tracks, access and natural drainage lines must all be taken into account. For best results design run off control as part of a property plan.

CATCHMENT APPROACH

The most effective way of controlling runoff is through a coordinated catchment approach.

CONTOUR BANKS

Contour banks provide simple, effective and long lasting protection from water erosion. Effective contour banks are:

Well planned and surveyed

Properly constructed
Carefully maintained
Connected to a well grassed waterway.

Contour bank construction and maintenance costs are low, especially when the long life of the banks is taken into account.

WATERWAYS

Well grassed waterways are an essential part of a run off control system. Grassed waterways:

Safely conduct run off water through cultivated areas
Contain run off water, which helps to prevent flooding and water logging.

Dedicated catchment grass slopes are known as flumes.

About 40% (40 000 ha) of the land with a moderate potential for water erosion in a typical Soil Conservation District was protected with contour banks by the end of 1991.

SUSTAINABLE METHOD 2 – STUBBLE RETENTION

The retention of crop and pasture residues improves long term productivity and reduces soil degradation. Protection from erosion. Stubble retention :

Protects the soil from wind and water erosion
Adds organic matter to the soil, improving soil structure and fertility
Increases water infiltration
Protects the soil from raindrop action, reducing soil movement and surface sealing
Recycles plant nutrients]
Can dramatically increase earthworm activity.

EXAMPLE

A 2 tonne/ha wheat crop produces about 3 t/ha of stubble and chaff. When evenly spread, this will provide about 75% ground cover, and gives adequate protection from water erosion. Less stubble is required to protect soils from wind erosion. Generally, about 35% ground cover is adequate. Farmers in the district have successfully retained stubbles from 4 t/ha wheat crops.

SUCCESS WITH STUBBLE RETENTION

Most stubbles can be successfully retained provided there is adequate planning. For example:

begin stubble treatment at, or immediately after, harvest. this will allow the most time for the stubble to break down before seeding or pasture regeneration.

keep as much stubble as possible on the soil surface. this provides the greatest soil protection and a better seedbed. most of the problems experienced with stubble retention are caused by incorporating stubble into the seedbed.

break stubbles into manageable lengths (usually 15 cm or less). it is the length of the stubble, not the quantity, that causes blockages in machinery. avoid repeated harrowing or working just to break up or bury stubble. the damage these extra cultivations do to the soil structure outweighs the benefits of keeping stubble.

grain legume stubbles need careful management as they are highly prone to erosion. grazing aggravates the erosion risk.

stubble is too valuable to burn. when stubbles are burnt, all of the nitrogen and sulphur are lost. burn only as a last resort and use a cold burn after the opening rains.

When the stubble from a 2 t/ha Spear wheat crop is burnt about 15 kg of nitrogen is lost per hectare. This is equivalent to the nitrogen contained in 34 kg of urea.

SUSTAINABLE METHOD 3 - REDUCE TILLAGE

Of all farm practices, cultivation is the greatest destroyer of the soil. Reduced tillage systems limit cultivation and the consequent soil erosion and decline in soil structure. Reduced tillage results in improved crop emergence, root growth, crop yield, and overall farm viability.

ACTIONS TO REDUCE CULTIVATIONS:

replace cultivations with herbicides
use chemical topping, spray grazing or slashing of pastures to reduce weed populations before cropping.
cultivate only when weeds are present
control crop diseases with appropriate rotations.

The degree to which cultivation can be reduced depends on getting other management factors right, particularly weed control throughout the rotation. In the light of increasing herbicide resistance, some cultivation for weed control will be necessary in the rotation. In the long term, it is the total number of cultivations over the rotation that is important.

The loss of 1 mm of topsoil represents 10 to 12 t/ha. Such losses occur frequently on bare or sloping soils and often go unnoticed.

SUSTAINABLE METHOD 4 - DIRECT DRILLING

Direct drilling, or the sowing of a crop into unworked soil, is the ultimate form of reduced tillage. Any weeds present before sowing are controlled with herbicides. Direct drilling:

is markedly superior to other forms of reduced tillage in lifting soil organic matter and improving soil structure.
increases rainfall infiltration and minimises erosion
enables higher yields through more timely sowing
reduces the use of machinery and fuel
encourages the proliferation of earthworms.

Dust lost through wind erosion is the most fertile part of the soil. Concentrations of 60 ppm available phosphorous have been recorded in dust samples that came from a paddock with an average concentration of 24 ppm available phosphorous.

SUSTAINABLE METHOD 5 - IMPROVE SOIL STRUCTURE AND ORGANIC MATTER

Soil structure and organic matter are closely related and play a vital role in preventing soil erosion and maintaining crop production and overall farm viability. Well structured soils:

are porous
are friable
have stable soil aggregates or crumbs
are resistant to erosion, compaction and formation of surface crust
allow quick water infiltration
good germination, seedling emergence and root growth
good aeration
easy working.

SOIL STRUCTURE

Refers to the way individual soil particles of sand, silt and clay are bound together. The structure of a soil is influenced by its physical and chemical properties, its organic matter content and the activity of soil organisms.

ORGANIC MATTER:

maintains good soil structure
improves the chemical and biological fertility of the soil
contains almost all the soil nitrogen reserves
is the main soil binding agent in sandy soils.

Organic matter or humus is formed by the decomposition of plant and animal residues by micro organisms. In most soils, about 95% of the nitrogen is present in the organic matter. Only a small proportion of this is released each year for use by a crop.

SUSTAINABLE METHOD 6 - SOIL STRUCTURE AND ORGANIC MATTER CAN BE IMPROVED

Improving soil structure is a long term process and relies on increasing the organic matter content of the soil:

use a rotation that includes a vigorous legume pasture phase
reduce tillage
retain stubbles
monitor organic matter through soil tests for organic carbon
apply adequate fertiliser to crops
apply gypsum to responsive soils.

The object is to maintain high organic matter levels. Restoring depleted organic matter is a difficult and long term process.

SOIL TYPE, SOIL STRUCTURE AND ORGANIC MATTER

Soil structure and organic matter vary considerably with soil type and management. Red brown earth soils, particularly those with a sandy loam to loam surface texture, are highly susceptible to a decline in soil structure and organic matter.

Sandy soils have a low potential for a decline in structure but are highly susceptible to a decline in organic matter. Calcareous loamy soils have a low potential for a decline in structure because of their high lime content. They are prone to a decline in organic matter but this is often a slow process because they have naturally high levels of organic matter.

Dark brown cracking clay soils have a low potential for a decline in structure and organic matter. This is because of their clay content and naturally high levels of organic matter.

GROW VIGOROUS LEGUME PASTURES

Planned rotations that include a vigorous legume pasture phase are essential for the long term well being of the land and for the production of high yielding crops and high quality grain.

Because of the variation in rainfall, soil types and rotations across Australia's agricultural areas a number of different pasture legumes, including medics, clovers and vetches, have a role.

The benefits of a vigorous legume pasture phase:

improved soil structure
increased organic matter
improved nitrogen fertility
increased earthworm and microbial populations
some reduction in crop diseases and weeds.

EXAMPLE

A good legume pasture can increase soil nitrogen by more than 80 kg/ha in one season. This is equivalent to at least 170 kg/ha of urea. Most pastures consist of annual medics and clovers because of their ability to regenerate after crops and persist in pasture phases.

ANNUAL MEDICS:

are generally adapted to neutral to alkaline soils
are suited to lower rainfall than are clovers and dominate where the rainfall is less than 375 mm.
are well suited to regular cropping rotations because they have a high proportion of hard seeds.

SUBTERRANEAN CLOVERS:

are generally suited to neutral to acid soils
require at least 400 mm annual rainfall
produce fewer hard seeds than do medics and are therefore less suited to regular cropping rotations.
are well suited to permanent pastures.

HOW TO GET THE BEST OUT OF ANNUAL LEGUME PASTURES

when selecting varieties pay careful attention to farming system, rainfall and soil texture and ph.
sow at the recommended rate
use mixtures in paddocks with several soil types
defer grazing during seedling establishment
restrict grazing from the onset of flowering and graze judiciously over summer and autumn to ensure there will be some seed reserves.
control pests such as red legged earth mite, lucerne flea and aphids.

Rotations that include vigorous pastures provide the highest yields of high protein wheat.

SUSTAINABLE METHOD 7 - PLAN FERTILIZER USE

Planning fertiliser use is essential to prevent the depletion of soil nutrients through removal in farm products and to improve or maintain soil fertility for optimum crop and pasture yields. Grain legumes remove considerably more nutrients than do cereals. For example, one tonne of peas contains about 39 kg of nitrogen, 3.8 kg of phosphorus and 2.4 kg of sulphur, while one tonne of wheat contains about 21 kg of nitrogen, 2.6 kg of phosphorus and 1.6 kg of sulphur.

To develop a planned fertiliser program, determine the nutrient status of soils, crops and pastures by keeping accurate paddock records and using soil and plant tests. The main nutrient deficiencies that occur in Australian agriculture are nitrogen, phosphorus and zinc.

NITROGEN (N)

Nitrogen deficiency is considered by many to be the greatest constraint to cereal yields. Nitrogen is also a critical factor for achieving adequate protein levels in wheat grain. To overcome a nitrogen deficiency:

in the short term, apply nitrogen fertiliser
in the long term, increase the reserve of nitrogen rich soil organic matter through vigorous legume pastures.

PHOSPHOROUS (P)

Most Australian soils are deficient in phosphorus in their natural state. Regular additions of phosphate fertiliser are required for maximum growth of crops and pastures.

ZINC

Zinc deficiency commonly occurs but in varying in degrees with soil type and management. The most reliable method for identifying zinc deficiency is to tissue test crops and pastures.

SUSTAINABLE METHOD 8 - REHABILITATION OF SALTLAND

The prevention and rehabilitation of dryland salinity requires a catchment approach to water use. The main issues are:

prevention of ground water recharge on unaffected areas
increasing productivity on affected areas.

The aim is to minimise the amount of ground water recharge by maximising water use. Dryland salinity is caused by changes in water use that have occurred since European settlement. deep rooted perennial vegetation has been replaced by shallow rooted annual plants that use less water. Groundwater levels rise, mobilising salt stored in the landscape. Where this water gets within I to 2 m of the soil surface, saltland develops.

ON UNAFFECTED LAND:

use crop and pasture species that use a lot of water such as lucerne
grow high yielding crops and pastures to maximise water use
establish perennial vegetation either agricultural or native species on land of low productivity such as rocky outcrops, paddock corners and laneways.

ON LAND THAT IS MODERATELY SALINE:

Use salt tolerant crops such as barley
Maintain surface cover at all times to prevent salt from concentrating at the soil surface.

ON LAND THAT IS HIGHLY SALINE:

That is, too saline for broadacre crops:

fence the area

where the ground water is too saline for lucerne, establish and maintain pasture using salt tolerant species, such as tall wheat grass, puccinelia, strawberry clover and saltbush.

control grazing so that surface cover remains at all times to prevent salt from concentrating at the soil surface.

install structures to control water run on from adjacent areas

establish salt tolerant native trees and shrubs to increase water use.

SUSTAINABLE METHOD 9 - CONSERVE AND ESTABLISH NATIVE VEGETATION

CONSERVE REMNANT NATIVE VEGETATION

Most of the original native vegetation, including mallee scrub, shrublands and open grasslands, have removed for agricultural development. Grazing, burning, fragmentation and isolation, and invasion by introduced plants and animals has degraded much of what remains. Sound management of the remaining native vegetation is essential to ensure that regeneration occurs:

fence to control grazing
control animal and plant pests
on grazed areas, control grazing pressure to enable regeneration
enter into heritage agreements with the appropriate department.

ESTABLISH NATIVE VEGETATION

Native vegetation can improve agricultural production and should be established wherever possible, for example:

for the protection of crops, pastures and livestock

to increase water use on areas of low productivity such as rocky reefs, shallow soils and paddock corners, and on and around saline areas and areas prone to waterlogging.

to stabilise erosion gullies

for woodlots, honey and amenity purposes.

Old native trees, even when dead, are especially important as more than one quarter of native bird species use tree hollows for shelter and breeding.

SUSTAINABLE METHOD 10 - STABILISE SANDHILLS AND SANDY SOILS

Sandhills and sandy soils that are associated with the dune swale system on the coastal plains are highly prone to wind erosion. Increasing the stability of these soils will reduce the risk of wind erosion:

Maintain ground cover
Minimise soil disturbance
Improve soil fertility and organic matter
Match crop type to the capability of the land
Control root diseases
Plan the layout of property improvements
Eradicate rabbits.

STABILISING LARGE SANDHILLS

Large sandhills are best fenced off and used for permanent pasture but an occasional crop may be necessary to reclaim eroded areas, improve soil fertility, control weeds or renovate pastures:

sow with a cereal crop that will provide good ground cover, for example cereal rye, barley or triticale.
sow sandhills at the start of the cropping program
use adequate amounts of nitrogen and phosphorous fertiliser
resow as soon as possible if wind damage occurs
use minimum tillage or direct drilling
retain crop stubbles and pasture residues and control grazing to maintain at least 70% ground cover.

SUSTAINABLE METHOD 11 - PLAN THE PROPERTY

All land should be used within its capability so that it is in as good as, or better, condition for future generations. The best way to achieve this is to develop and implement a property plan. Property planning involves consideration of all the components of the property including climate, topography, soil, native vegetation, property improvements, crops and livestock, pastures, economics and personal goals, and their integration into a profitable, sustainable and efficient farming system:

assess the resources of the property and the capability of the land
plan the best arrangement of property improvements
identify the land use and management options to which the land is suited
establish a financial plan, priorities and a work program to implement the plan.

Soil conservation boards encourage land holders to prepare property plans, and are authorised to approve property plans provided they conform with their district plans.

EXAMPLES OF LAND CLASSES AND THEIR MANAGEMENT

Land with a potential for wind erosion:

II Standard management of minimum tillage, stubble retention and a rotation that includes a pasture phase.

III Standard management, with crops restricted to cereals and, on average, a rotation with no more than one crop in two years.

LAND CAPABILITY

Assessing the capability of the land is the first step in property planning. Eight land classes are used to rank agricultural land from highest to lowest capability. The capability of the land, and therefore the land class into which it is placed, depends on the nature and severity of the limitations present (for example water erosion potential, wind erosion potential, rockiness and salinity). Examples of land classes and their management.

EXAMPLES OF LAND CLASSES AND THEIR MANAGEMENT

Land with a potential for water erosion.

I Standard management of minimum tillage, stubble retention, and a rotation that includes a pasture phase.

II Standard management plus contour cultivation

III Standard management plus contour banks, waterways and reduced use of grain legumes

IV Improved pasture and controlled grazing to maintain
ground cover

Vl Non arable because of rockiness and steep slopes. Grazed carefully to maintain ground cover.

See indicators of farm performance

REFERENCES

Cook AV & Ronan GS (1991), "Approaches to farm business difficulty and insolvancy", The Australian Farm Manager, Vol 2, No4, August, pp2-4.

Martin P & oers (2001), “Farm Performance”, Australian Farm Surveys Report 2001, ABARE

Martin S et al (1991), "Banking and the rural sector", Ch 16 in "A pocket full of change: Banking and deregulation", House of Reps Standing Comm on Finance & Pub Admin, November, pp 267-288.

Peterson DC, Dunne SH, Morris PC & Knopke P (1991), "Developments in debt for broadcasting agriculture", Agriculture and Resources Quarterly 3 (3), September, pp 349-360.

Cook AV & Ronan G, (1993), "Performance indicators to assess the business position of farms under financial pressure", unpublihsed.