Determining slope and soil texture
Slope can be expressed in a number of ways. One is a percentage which can also be converted to the amount of fall over a 100 metre distance. The table below shows the conversion of percent slope to fall over 100 metres. A visual assessment can be made using the amount of fall over 100 metres and converting back to a percentage.
Table 1:Conversion of percent slope to fall over 100 metres
Amount of fall over a 100 metre distance
Flat with no fall
A clinometer can be used for a more accurate measurement of slope. Clinometer apps are available for smart phones.
A dumpy level can also be used to accurately determine the fall over 100 metres or more (or less).
Slope may also be determined using a GPS or topographic map. To determine the slope using a topographic map you will need the rise (the difference in elevation between two points) and the run (the distance between two points calculated using the map scale). Slope can then be determined with the following calculation: rise / run x 100 = % slope
Assessing Soil Texture
Soil texture refers to how coarse or fine the soil is: that is, how much sand, silt and clay it contains. Texture has a major influence on how much water a soil can hold. Generally, the smaller and finer the soil particles (the more silt and clay), the more water a soil can hold, and the less susceptible it is to wind erosion with adequate rainfall.
Soil texture can be estimated by hand using the ribboning technique, noting that it takes practice to produce a consistent result.
Carry out this ribbon test on a sample of soil from the area to be cleared using the Code. If soil differs across the area to be cleared, assess each area separately.
Do this several times for confirmation and compare the average ribbon length with those in Table 4 below. Each soil texture is classified within a ribbon length range (for example, sandy clay loam ribbon length is 25 to 40 mm long).
Once a consistent ribbon length is being produced, you can be reasonably confident that the correct soil texture has been identified.
Table 2: Soils textures using the ribboning technique
Behaviour of the
Ball will not form
Ball just holds together
Ball forms, sticky-clay stains fingers
Ball forms, feels sandy, but spongy
Ball forms, feels smooth and silky
Ball forms, feels smooth and spongy
Sandy clay loam
Ball is firm, feels sandy and plastic
Silty clay loam
Ball is firm, smooth, silky, plastic
Ball firm, feels smooth and plastic
Ball very strong, feels plastic
Ball very strong, feels like plasticine
Ball very strong, stiff plasticine