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Lowan Land System


Lowan Land System Figure 47 (PDF - 252KB)
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Plate 34 - The Lowan land-system is a plain abounding with swamps, has some low parallel ridges and supported woodlands of gums
Plate 34 - The Lowan land-system is a plain abounding with swamps, has some low parallel ridges and supported woodlands of gums
In the extreme north-west of the survey area is the south-westerly extremity of a land-system which is extensive in tile Shire of Kowree, the Lowan land-system.

Where it is widespread, as in the Shire of Kowree, the Lowan land-system is a regionally flat plain of Miocene limestone abounding with circular swamps and carrying parallel ridges running in a north-north-westerly direction. Regional drainage is very slow and is confined to the lines of circular swamps, or through the swamps into the underlying limestone, thus feeding the artesian basin of southern South Australia. The only dissection pattern is a very weak one on the south-western edge, back from the Kanawinka fault. The ridges, composed of sandy material, are fairly prominent in the north and east of Kowree Shire, and evenly spaced at intervals of about one mile, but further west they become less prominent, and further south they are more diffuse and irregular. Consequently, in the part of the land-system lying within the survey area, the slight irregularities of relief can barely be recognized as part of the ridge system, which in fact they are. Moreover, in this part of the land-system, there is weak dissection back from the Kanawinka fault by streams such as Mosquito Creek.

All that part of the land-system which is in the survey area falls into the Apsley land-unit. This, as described in a previous report on the soils of Kowree Shire (Blackburn and Gibbons 1956), is a generally flat plain, elevated above the coastal plains to the west and separated from them by the Kanawinka fault.

This particular part of the land-system therefore may be regarded as a slight but extensive plateau. It has numerous shallow swamps, slight rises, and is weakly drained by streams from the west. In the survey area, it occupies about 52,000 acres, virtually all of which has been alienated.

Soils are chiefly brown solodic soils and solodised-solonetz, developed upon either the limestone or the Pleistocene veneer covering it. In the swamps, some of the soils are gilgaied solodic soils and others are mottled organic sands and sandy clays, which come into the category of meadow soils. On the slight rises are brown solodic soils with rather deeper A horizons.

Vegetation is fairly uniform throughout the Apsley land-unit, and is predominantly red gum (Eucalyptus camaldulensis) in savannah woodland formation. Yellow gum (E. leucoxylon) is found also and the pink gum (E. Jasciculosa) is occasional on drier sites such as the deeper solodic soils on rises. Heath species are generally absent now, and grasses, both native and introduced, are dominant under the red gum; honeysuckle (Banksia marginata), according to early records was prevalent in the under-storey or ground-storey but is now rare. The whole land-unit is the more northerly counterpart of the gum flats of the Rosencath and Kanawinka land-units. In these gum flats, grasses are characteristic of the ground-storey, as opposed to heaths for other components of the Kanawinka land-system.
The pastoral potential of the unit has always been regarded as high, as shown by the very high proportion, 97.5 per cent, of occupied country and by the generally extensive clearing. Until about fifteen or even ten years ago, most of the grazing was on native pasture. However, the soils respond quickly to improvement with superphosphate and clovers, and now there are only small areas left of native pastures.

The soils are moderately fertile and quite capable of easy development to grass and clover pastures and to crops, in the moderate but reliable 24-inch rainfall. Kybibolite Research Station in South Australia is on somewhat similar country, and has demonstrated the capabilities of the area; most of the findings coining from that Station would apply to the Apsley unit. Beckwith and de Vries (1959) have shown the low reserves of potassium and copper in the surface of the solodised solonetz soil of the Kowree Shire part of this unit, and this probably means that these elements will become deficient when farming becomes more intensive. These workers found reserves of potassium in the clayey subsoil, but considered that poor aeration in the A, horizon would prevent pasture species from using these reserves. These views may not apply to deep-rooted species.

Cultivation or cropping is not widely practised but as the area is suitable for the production of meadow hay, fodder crops and even cash crops, it is likely that these enterprises will become much more important. Low-lying areas and swamps, which do not produce much now, can become an asset if sown to perennial clovers such as strawberry clover. The suggestions made for the Strathdownie land-system regarding impounding of swamp water and irrigating of the swamp beds apply equally to this land-system.

The erosion hazard of the north-eastern land-units of this land-system is moderate. It decreases to the south and west, however, so that in the Apsley land-unit it is very low because here, the slopes are neither steep enough nor long enough for concentration of rapidly moving water, nor is there a sufficient source of sand capable of being blown. The Mosquito Creek is an exception, and is slightly eroded.

To summarise, the Lowan land-system is a regionally flat plain of Miocene deposits covered with a veneer of Pleistocene deposits, and the Apsley land-unit at its south-western extremity forms a slight plateau bounded by the Kanawinka fault line. It abounds in numerous shallow, seasonal, circular swamps, has a few slight rises and is characteristically timbered with red gum. The solodic and solonetzic soils and moderate but reliable rainfall combine to make it excellent grazing country capable of more intensive farming. There is very little erosion.

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