Farming in a variable climate

This section of the e-farm describes Australia's extremely variable climate, and the impact on farming operations at Tocal. The major climatic influence on farming, rainfall, is very unreliable and averages don't help to predict seasonal rainfall. So what is the likelihood of receiving this rainfall?

Probability tables can help to answer this question. Computer software packages, for example, Australian Rainman, can create probability tables for you. Using probability tables and the rainfall and evaporation rates, we can make the following observations:

• the chances of receiving effective rainfall is high in autumn and throughout winter
• the chances of receiving effective rainfall in spring and early summer is only around 25-30 percent
• plant growth is likely to be assured in most autumns and early winter
• unless there is carry-over soil moisture, growth in spring will be less than ideal due to low soil moisture levels.

It is also very useful to have experienced varying conditions on a property. Experience and farm records show us that on Tocal:

• Dairy: A good year on the dairy is one which has a fairly dry January/February so there is not too much growth of kikuyu in which to sow winter pasture. Success in establishing early winter feed ensures the winter feed gap is filled. A poor year on the dairy is a wet, late summer/autumn and wet winter, or both. The hill country bogs up and can’t be worked with machinery or grazed. The soil becomes waterlogged and nitrogen is lost. This results in less plant growth and the quality of plant material falls. The climate at Tocal makes haymaking difficult. It is said that if you live with the hay, that is, mow, rake, bale and cart at exactly the right time, you can make a fair amount of hay. Opportunities are missed if you put the hay second to other farm activities.
• Beef and Sheep: The biggest problem at Tocal is that of reliably finishing cattle. Late winter/spring westerlies can turn a reasonable spring into a poor one in a fortnight or three weeks. The flats and basalt country are less vulnerable, because the soil holds more moisture. Cold conditions are rarely a problem for lambs and ewes, compared to the Tablelands. Tocal College has always had both autumn and spring calving herds. The spring calves usually have slightly heavier weaning weights than the autumn calves.
• Poultry: High temperatures and, even worse, high humidity, are the only real threats. If the sheds are carrying large birds (6-7 weeks - ready to be turned off), temperatures of over 35°C can cause mortalities. Fogging, consistent monitoring and adjusting, and walking through the birds to keep them moving are the only ways to reduce deaths. In the 1991 drought, the salt levels in Webbers Creek caused blockages in the fogging jets, with the result that a large fresh-water storage dam was constructed at Clements Farm in 1995 to overcome any future occurrences.
• Pastures: High summer rainfall results in massive paspalum growth. This can be a problem when the paspalum seedhead becomes infected with an ergot, which can poison stock, and the dense growth of paspalum can smother germinating subterranean clover. A dry summer and reasonable autumn will usually give excellent growth of Fireweed (Senecio madagascariensis). This is because the Fireweed seed requires light to germinate. The sparse groundcover enables light to reach the seed and a ready seedbed is available. The same conditions favour the germination of subclover. October/November can be quite dry, and this causes difficulty in establishing summer crops. Forage sorghums are easier to establish than maize, given harsh conditions. Because of the higher temperatures at Tocal, winter feed (for example, oats and ryegrass) is rarely as good in quality as that grown inland. The digestibility of these grasses is higher if grown under cooler conditions. So a cold winter at Tocal is not necessarily bad.