Over-sowing pastures

Over-sowing is the sowing of a non-native species into an existing native groundcover or pasture (typically with 50-75% density) to increase production for grazing purposes such as increasing winter forage.

When to consider over-sowing

Following flood, over-sowing with winter forages is a good way to address potential feed shortages. It can put more pressure on any surviving pasture within that paddock but will reduce grazing pressure overall and limit damage to soil by conventional sowing equipment.

Over-sowing with legumes into an existing pasture is another method for improving pasture composition. If there is already a good pasture base to work with, over-sowing is faster, less expensive, and minimises disturbance.

When over-sowing is not recommended

Over-sowing exotics into native ground layer vegetation can have a negative effect on vegetation communities. It is not recommended in high-conservation value grassland areas.

Over-sowing perennial pasture grasses is not recommended as they can modify the long-term habitat structure.

Over-sowing on Category 2 - Sensitive regulated land must be to the minimum extent necessary. Read more about over-sowing as part of the Sustainable Grazing allowable activity. 

Over-sowing summer grasses for winter feed-gap management

Through the North Coast and Hunter regions of NSW, most beef pastures comprise tropical species such as Paspalum (Paspalum dilatatum), Kikuyu (Pennisteum clandestinum) or Setaria (Setaria sphacelatea). These species do not grow during winter.

In poor seasons when reduced stocking rates and supplementary feeding options are not profitable, the other alternative to addressing the winter feed gap is to plant a winter active pasture or crop.

• Grass seed can be broadcast across a paddock, either by hand and bucket or via a fertilizer spinner and quad bike or tractor.
• Cattle are then used to graze the summer grass and trample the seed into the ground.
• Portable electric fencing is used to concentrate grazing pressure over the target area.

While this sowing method is sub-optimal and re-sowing may be required to even out pasture density, it can be beneficial in a wet year when conventional sowing could damage soil. 

Varieties suited to over-sowing

Early maturing, tetraploid Westerwold type varieties of Annual Italian Ryegrass (Lolium multiflorum ssp.
westerwoldicum) are ideal for this technique as they produce a bulk of feed quickly in autumn/winter.

These varieties have double the number of chromosomes as regular (diploid) types. They have larger seeds with better energy reserves to cope with sub-optimal sowing conditions.

Choosing a less expensive variety such as tetraploid ‘Tetila’ allows a financial buffer to re-sow paddocks if poor establishment occurs as a result of patchy distribution, or hot and dry follow up weather.

What to do 

4 weeks before sowing

• Cease fertilizer application.
• Graze hard, mulch allowing sufficient time for the mulched material to break down.
• Graze down to 4-5cm. 

Sowing time 

• Set up electric fences.
• Broadcast the seed (up to four days ahead of grazing).
• Let cattle in to graze and trample the seed in. 

2 weeks after sowing 

• Let cattle in for a light grazing to nip off summer grass re-growth to prevent shading of ryegrass.
• Cattle will need to be moved off again quickly (2-6 hours) to prevent excess trampling.
• After the first grazing apply a half normal rate of nitrogen fertilizer e.g 50kg Urea/Ha. 

4 weeks after sowing 

• Graze as above if the summer grass looks like it is shading the ryegrass seedling. 

First full grazing 

• First full grazing of ryegrass seedlings (leave 6cm residual) should be at about 6 weeks.
• Apply full rate of nitrogen fertilizer.

Subsequent grazing 

• Graze at 3 leaf stage to optimize pasture resilience and feed quality (by May grazing should be no less than 30 day interval).
• Move cattle on after two days.
• Use a back fence when strip grazing to stop cattle grazing regrowth (back-grazing) as this severely reduces ryegrass growth.
• Apply usual nitrogen fertilizer every second grazing, depending on rainfall.

Tips for success 

• Ryegrass seeds have 6-7 days of storage carbohydrates that the seedling uses to grow roots and early leaves. If the seedling is not producing its own carbohydrates via photosynthesis after this period it will die.
• Minimise thatch (Kikuyu). Kikuyu pastures accumulate a large volume of stem and dead material over the summer. When seeds are covered by this material the seedlings can die from lack of light and compounds released from the decomposing thatch. This is why we need to mulch hard about a month before sowing.
• Don't sow deep. Sowing seed too deep (more than 1cm) is a common cause of poor ryegrass establishment. The seedling uses up its energy reserves before it can emerge.
• Minimise shading. Too much shade is a very effective way to kill young seedlings, and is a particular problem when over-sowing into vigorous tropical pastures such as Kikuyu. It is important to prevent shading from summer pastures in the first six weeks after sowing.
• Follow up irrigation should be considered in the first 6 weeks of the establishment phase if there is insufficient rainfall.