Prepared by Bob Holloway
In the early days of colonisation, farmers adopted the farming systems they had learned in Europe and quickly settled into wheat followed by fallow rotation. This rapidly depleted the naturally low soil fertility and exposed the soil to erosion. Yields fluctuated dramatically with the changing seasons and crop diseases, but the general trend over time was for yields to fall. In their experiments at Roseworthy Agricultural College in the 1880’s Professors Custance and Lowrie showed that the key plant nutrient missing from infertile soils after years of cropping was phosphorus. The general decline in yields at the time was halted when superphosphate was applied to the soil.
Cropping rotations were extended to include hay and pasture paddocks to “rest” the soil and control weeds and diseases. However, prior to the 1940’s fallow was still widely adopted in the rotation with wheat and these led to enormous issues with wind and water erosion. Dividing land into classes according to its slope combined with farm planning in the 1950’s initiated the first steps in halting the serious water erosion problems in the higher rainfall areas of the State. The simultaneous emergence of subterranean clovers and medics in rotation with cropping improved soil structure and fertility via the fixation of atmospheric nitrogen by these legume pastures. This ley farming system was widely adopted in the 1950’s when wool and meat were in demand. It was recognised that the use of superphosphate was critical in the success of this system and a government funded superphosphate subsidy from 1963 to 1973 saw large volumes of superphosphate applied throughout SA. This was responsible for long term benefits in terms of improving soil fertility.
During the late 1960’s and 1970’s, oilseeds, lupins, triticale, pulses, lentils, canola and vetch were widely introduced into rotations. The control of the major cereal root disease cereal cyst nematode (CCN) by the barley variety Galleon was a major advance in breeding technology. Cereal-legume rotations offered interactive benefits of reducing root disease and enhancing soil fertility. Together with the growing recognition that minimising cultivation (the ultimate in this respect being zero-till) allowed continuous cropping without loss of soil physical and chemical fertility. During this time, livestock disappeared from many farms although in the early years of the 21st century, stagnant cereal prices and improving prices of sheep meat have led to a resurgence of grazing flocks on many properties.
Farming systems in SA have changed significantly over the past 150 years and will have to continue to change, driven by environmental and economic pressures.