Man-made soil erosion can occur whenever the natural environment is disturbed by mechanical farming operations, roadways, timber clearing, urban development and overgrazing.
Sloping cultivated land is particularly susceptible to soil erosion during heavy rainfall. The various State Soil Conservation Services provide a number of services to commercial landholders but not necessarily to ‘hobby farmers:
The service can prepare detailed farm plans to ensure maximum land protection in order to maintain or indeed increase agricultural production. The NSW service owns a considerable amount of earthmoving equipment which can be hired by landholders.
NSW landholders unable to pay for soil conservation works may apply for special loans. These funds are only available to landholders dependent on farming for their main income.
Government intervention in soil management has increased in recent years because of the pressure now being placed on land to produce more income. Overstocking and excessive ploughing can ruin the structure of the soil, making it susceptible to a loss of top soil.
Closer settlement is also putting further pressures on the land. Four-wheel-drive clubs and trail bike riders are examples of new causes of soil erosion. It is not only the loss of soil which is a problem but also the resultant downstream silting of dams and creeks. Many farm dams now hold only half the water they contained twenty years ago.
How much land should I buy?
Before purchasing a block of land for your alternative lifestyle, spend some time considering what is your long-term requirement. Select a lot size in a locality to suit your needs.
For example, if you wish to supplement your existing income by grazing or cropping a ten-hectare lot, ensure that the land is productive, cleared and pasture improved. Avoid purchasing a one-to-five hectare lot just for residential purposes in an essentially rural area.
A rural retreat can be developed on ten hectares of isolated rough terrain, uncleared and consisting of poor quality soils. Properly managed, it can be an ideal retreat and usually sells for far less than a more developed property.
Should a part-time commercial enterprise be envisaged, then a larger block, say forty hectares, would be needed. Whatever your needs, careful selection is necessary to avoid splitting prime agricultural farmland into uneconomic units. This is a waste of valuable and limited resources.
Ground rules:
Before making a commitment to a small holding, first of all identify the natural factors that will influence your lifestyle and its agricultural objectives. The type of soils, climate, rainfall, drainage, landform, vegetation and existing erosion problems all need to be assessed.
Climate:
Climate is one of the major factors that hobby farmers and rural residential seekers should consider. Important climatic factors are temperature and moisture availability (ie, frost occurrence and severity, and rainfall and evaporation).
The type of land use proposed will alter the values at which these become critical enough to limit such important factors as plant growth and productivity.
In some areas, summer rainfall amount and/or intensity is an additional climatic factor which must be considered, particularly as it affects soil erosion.
Different soil types dictate different uses:
All agriculture depends ultimately on the capacity of the top layers of the soil to grow and sustain the growth of plants of one sort or another. Agricultural implements disturb the top soil, and rainfall infiltrates or runs off it. Proper management of the soil ensures that it remains as a natural resource.
Mismanagement can easily lead to soil erosion with the resultant permanent loss of that natural resource. The Department of Agriculture and/or the Soil Conservation Service should be consulted as to the best crops that are suited to a particular climatic area and soil type.
It will be important for prospective hobby farmers to assess the soil and vegetation cover on a block. Vegetation protects the soil by creating a canopy which reduces the impact of falling raindrops on the soil. Vegetation also reduces excessive runoff, and a healthy root system binds the soil together.
Soil fertility:
The soil’s fertility is its ability to support plant life. Low fertility in soils can be caused by a number of factors, broadly classified as either physical or chemical. Physical features of the soil are water retention features, air space, particle size distribution, structure and texture.
The chemical features of the soil are related to the acid/alkaline balance and to plant nutrient availability. Low fertility can also be attributed to excessive salt levels.
Naturally, climate plays a dominant part in the growth of crops or pasture, and the rainfall/evaporation pattern will determine what areas can be developed for agriculture or pasture improvement.
The removal of topsoil by erosion will affect the soil’s potential for more intensive use of the land for crop growing. This is because the nutrients which are of major importance to crop growth tend to be concentrated in the surface soil.
The subsoil is important in relation to drainage, water-holding capacity, growth of deep-rooting plants and long-term supply of minerals and nutrients.
Where to buy the mountains or the valleys?
The landform features of a block of land will determine the type of agricultural uses which may be undertaken on the block. Landform factors will also determine site suitability for locating buildings, roads and dam sites.
The slope of the land also limits its uses because erosion problems increase with steepness. Steep slopes impose increasing difficulty on the use of machinery for ploughing, cultivating, harvesting or earthworks.
The recommended maximum limit for regular cultivation is about ten per cent. Above this slope the erosion hazard is too great to permit safe cultivation. The recommended maximum slope limit for grazing varies between thirty and fifty per cent. Slopes above thirty per cent correspond closely to the areas that can be classified as ‘Protected Lands’, as defined in the Soil Conservation Act.
Slopes greater than fifty per cent are best left undisturbed. The most suitable uses of these slopes are those compatible with the preservation of the natural vegetation, namely, water supply catchments, wildlife refuges, national and State parks, and scenic areas. Where clearing has occurred the slopes are of little grazing value and usually present major problems of management.
Soils and buildings:
There are a number of soil properties which need to be considered when selecting a site to locate buildings on the hobby farm lot. These can be affected by other site features such as land slope, geology and drainage factors.
- Susceptibility to soil movement (engineering properties)
- Shrink-swell potential (engineering properties)
- Suitability for foundation material (engineering properties)
- Soil dispersibility and erodibility
- Permeability
- Salinity
Consultation with a qualified geotechnical engineer is advisable in selecting a suitable site.
Soils and earthworks:
Make sure that suitable sites are available on the lot for the construction of a stable dam of adequate capacity. Advice on catchment hydrology and soil problems associated with structural works is essential.
The earth embankment of a contour bank, a dam, or a gully control structure must be designed and constructed so that there is no appreciable amount of water movement through the bank.
It will then be able to retain its position, shape and ability to retard water movement over time. Three general considerations are therefore appropriate — permeability of the embankment, its compaction and its stability.
Roadways:
Apart from cultivation, roads and access tracks are the greatest contributors to accelerated soil erosion in the rural environment. They contribute to this by destroying ground cover, breaking down the soil surface, increasing runoff, diverting and concentrating this runoff, and causing unstable sections to develop in drainage lines.
Access roads must be constructed to be stable and trafficable in all weather conditions. Blocks which contain steep slopes, areas subject to soil movement, and areas of seasonally high water tables will present difficulties for locating roadways.
Water should not be concentrated by roadways or other works on unstable or erodible areas. Locating roadways slightly off the contour assists drainage control and aids in reducing erosion. If it is necessary for roadways to run up and down the slope, they should follow ridgelines to minimise erosion hazards. All inlets and outlets to culverts, drains, and road shoulders should be stabilised.
Stock control:
Restrictions will have to be placed on stock numbers and land use activities to ensure sufficient ground cover and pasture condition during critical seasonal times of the year, especially winter. Stock may also have to be removed during drought and low rainfall periods to prevent surface erosion and excessive runoff.
Provision will also have to be made for effective runoff control and effluent disposal associated with animal holding areas and horse yards.
On-site disposal of sewage:
Because it is most unlikely that hobby farm areas will be sewered, landform and soil conditions must be suitable for effective on-site disposal of household sewage. Consider factors like:
- Soil depth and permeability
- Seasonal variations in water table levels
- Climatic influences on evaporation and soil moisture, such as rainfall distribution, hours of sunshine, and wind conditions
- Possibility of seepage from higher land entering the absorption field
- Possibility of effluent seepage affecting neighbouring property, underground water supplies or nearby streams or lakes.
Information Sourced From:
Hobby Farming: The First Steps
