To get the most out of your perennial pasture there are many factors that need to be considered. Selecting the right species and variety is the first step in improving your pastures. However, if old or new varieties have not performed well on your farm then there may be underlying issues of soil fertility and grazing management that need to be addressed.
species and variety selection
Sowing a newly bred variety can produce an extra 300-500kg of milk solids or on sheep and beef farms could carry 30-50% more stock with faster animal growth rates than unimproved varieties. New winter-active phalaris cultivars can produce 50-100% more winter feed than Australian phalaris.
Annual rainfall is a good indicator of what species will suit your farm. Below shows the annual rainfall survival requirements of some perennial grasses.
Perennial ryegrass >650mm
Summer active cocksfoot >600mm
Summer dormant cocksfoot >350mm
Summer active tall fescue >600mm
Summer dormant tall fescue >500mm
The heading date of a grass is an integral factor to consider. For example, in perennial ryegrass, nearly 60% of its annual dry matter (DM) yield occurs around heading. To take advantage of this peak it is important to match the right heading date to your environment.
Early heading perennial ryegrass varieties, such as Rigby, have the DM production peak in late winter/early spring, so these varieties are best suited to early country. Mid heading varieties, like Caretaker II, are your “all-rounders” that can be used in most locations including dry and wet areas. Late heading varieties, like Cantina and Violet, are best suited to high rainfall, late country that holds moisture into early summer. If you plant a late flowering ryegrass in areas where the rainfall tends to dry up before the end of November, then there is potential of losing a large amount of feed.
Before sowing a pasture, a soil test should be carried out to determine any extra inputs needed before and after sowing. Nutrients in the soil for the plant are like vitamins for humans, a lack in one or all of them will see a decrease in productivity. Treat the latest genetics of your pasture like you do the latest genetics in your herd, they both won’t perform if you don’t feed them good quality food.
Aim for at least 75-85% pasture utilisation at grazing. Season and plant growth will determine when to move stock onto the next paddock. For example, spring rotations can be as little as 15 days, whereas winter rotations can be up to 60 days.
Monitoring leaf growth rate is a good indicator of when to graze pastures. With perennial ryegrass and fescue, the optimum time to graze is at the 2.5-3 leaf stage. If pasture is left to grow too high there can be an increase in diseases such as rust, a decrease in pasture utilisation by stock and reduced clover content. For phalaris and cocksfoot, the optimal time to graze is at the 4-leaf stage.
Measuring pasture height is also a good tool to determine grazing rotations. For a ryegrass pasture, a height of 15cm is approximately 2500 kg DM and is the height that is associated with the 2.5-3 leaf stage. This should be grazed down to 5cm which is approximately 1500 kg DM. If you graze below this it will slow down plant recovery and could affect persistency.
Keeping short grazing rotations in spring can keep the grass vegetative instead of it becoming reproductive. Each day a seed head appears, there is a loss in digestibility by 0.5%. If there are not enough stock available to utilise the spring growth of pastures, it is best to take paddocks out of the rotation for silage or hay production.
Economic and productive pastures come from being persistent, so it is important that you do not overgraze your pastures in summer.
If you focus on getting these factors correct, you are well on your way to a healthy, productive, and economic pasture.