Production
Estimates by the Australian Bureau of Statistics of the value of goods produced in South Australia in the year 1983-84 show that 34.4% were the products of farms, 12.4% the products of mines, quarries and gas-fields, 1.1% the products of fisheries and 52.1% were manufactured goods. The data for primary products are estimated at the point of leaving the farm, mine or fishing vessel, but no data are available for the value of logs at the point of extraction from the State's forests. The data for manufactured goods are the values added through the manufacturing process and therefore exclude the value of the raw materials and energy.
Agriculture
South Australian agricultural production is dominated by crops. In 1983-84 they accounted for 63% of the value of farm out-put compared with 22% for wool and other livestock products and 15% for livestock sold for slaughtering. In the nineteenth century wheat and wool were virtually the only farm products produced in South Australia which could sustain their cost of transport to distant markets. These two products still make up about 40% of the value of farm production; however, the mixture of products has diversified greatly during the twentieth century. Furthermore, farming methods have become much more finely tuned in order to maintain high yields in conditions of very low natural soil fertility and marked seasonal shortages of water.
By the early twentieth century most South Australian farmers were practising a simple wheat-fallow system with few livestock. After a year of fallow with frequent cultivation to suppress weeds and, it was believed, to conserve moisture, wheat was sown with superphosphate following the first autumn rains. However, this system was exploitative, and by the 1930s had led to deteriorated soil structure, depleted fertility, and wind and water erosion.
The solution to the farming dilemma was found in legumes, notably subterranean clover and various species of medics. These plants originated in the Mediterranean, and were introduced fortuitously to South Australia, possibly by the 1870s. They spread through much of the cereal zone when farmers began sowing superphosphate with their wheat, and grew as volunteer pastures on land which was not immediately ploughed up after the grain harvest. The medics and clovers are particularly useful because they set hard seed at the end of spring, evade the summer drought, and germinate in the next autumn, or the next but one. These pasture legumes, which are stimulated by superphosphate dressings, obtain nitrogen from the air and return it to the soil though decaying plant material and droppings of grazing animals.
Subterranean clover and the medics provided the basis for a ley system of farming in which grains and pastures are alternated, with the pasture phase supporting livestock, especially prime lambs. The spread of the ley system was accelerated by the replacement of horse-teams by tractors after the Second World War and by the high wool prices of the 1950s. It was a cheap and effective method of restoring structure and fertility to the worn-out wheatlands and of raising the yields of grain harvests, the number of livestock and the weight of fleeces. The South Australian experience was soon applied in other summer-dry farming areas of Australia. This particular ley system ranks among the most important Australian agricultural innovations of this century.
South Australians on farms and in workshops have made important contributions to Australia's list of farm machinery innovations. In 1843, J.W. Bull and G. Ridley developed the grain stripper, paving the way for successful export-oriented wheat farming in the 1850s. The most decisive South Australian innovation was probably the stump-jump plough developed in 1876 by Robert B. Smith at Kalkabury near Maitland on Yorke Peninsula. The original design was a three-furrow plough with a hinged arm attached to each plough share. On striking an obstruction such as a tree root or stone, any of the plough shares could rise out of the ground and return by the pressure of a weighted hinge after passing the obstacle. Robert's brother Clarence, a blacksmith, initially disparaged the invention but later manufactured stump-jump ploughs at Ardrossan and made many improvements including a six-furrow plough.
The simple weighted-hinge principle was later replaced by a strong clock-spring mechanism and is a feature of almost all South Australian tillage and seeding machinery. In contrast to the deep cultivation with mouldboard ploughs practised by nineteenth-century pioneers, shallow cultivation with disc ploughs, scarifiers and harrows is now the general practice. The stump-jump mechanism, a 'folk invention' from South Australia's Yorke Peninsula, is now widely used on farm machinery throughout Australia and in some western States of the USA.
