On any farm there may be several different pasture and feed sources (annual pasture, native or introduced perennial grass pastures, lucerne, grazing cereals, forage crops and crop stubbles) that can provide forage at different times of the year. Figure 8.4 shows the growth of lucerne and sub clover-based pastures at Dubbo. Your total farm feed supply determines how well an enterprise and stocking rate will suit your growing season. However, it is important to also consider the quality of the pasture at different times of the year. For example, only a small area of lucerne might be required to grow out late winter born lambs in the Dubbo region.

There are several ways to use the pasture growth data. The first option is to plot on a graph similar to figure 8.4, the pasture growth of each of the main pasture types on your farm. This data together with information on the area of each pasture can be entered into the MLA Feed Demand Calculator to generate an overall supply curve for your farm. In addition, the tool allows you to trial different stocking rates, lambing times etc and determine pasture deficits or surpluses.

Figure 8.4 Pasture supply curves for Dubbo, NSW. Summer active pastures can extend the growing season and provide land management benefits. Source: GrassGro®.

A second option is to manually work out the “average” pasture growth each month for your farm. This is relatively easy where there are only 2-3 pasture types on a farm. For example, assuming the data in Figure 8.4 is from a 1,000 ha farm with 800 ha sub clover pasture and 200 ha of lucerne, the average farm pasture growth per hectare in January is:

table to be added here

The same calculation can be undertaken for each month to determine the average pasture supply across the farm in an average year.

Figure 8.5 Average pasture growth curves (1965–2002) for four different environments. Kojonup, WA: annual pasture, good fertility; Bendigo, Vic: phalaris/sub clover pasture, good fertility; Armidale, NSW: native pasture (red grass)/sub clover, low fertility; Dubbo, NSW: annual pasture, moderate fertility. Source: GrassGro®.

A third thing to consider is the potential to use alternative pastures or forage sources to fill feed gaps. For the farm at Dubbo NSW shown in Figure 8.4, what options are there to graze cereals or use pasture growth promotants in July? Is there potential to use more summer active pastures to overcome feed gaps in summer? Local state agency staff or agronomists can provide advice on species to fill feed gaps.

Finally, with the assistance of your consultant or advisor, use tools (such as the computer model GrassGro®) to get more specific data for your pasture species, soil types and soil fertility levels and how changes to these will influence pasture growth and quality.