Pasture renovation - sowing

pasturesheepThis is the third in a series of four articles on pasture renovation by Dr Deric Charlton.

Oversowing
  • Here seed is spread on top of the existing pasture. Usually it’s done on land too steep or stony for cultivation.
  • Many farmers use “oversowing” when resowing pastures every year with Italian ryegrass, to boost pasture feed supply. This is “overdrilling”.
  • When oversowing, a fertiliser spinner or a topdressing aircraft broadcasts the seed.
Recipe for successful oversowing:
  • Graze off the old pasture as low as possible.
  • Broadcast it, mixing the seed with sand as a filler.
  • Make sure the sown seed contacts the soil surface.
  • “Hoof-an-tooth treading with stock can do this. Sheep are ideal.
  • A Cambridge (ribbed) roller is good for consolidation after sowing.
  • If safe enough, chain harrows can be used and then rolled.
  • Spread fertiliser the same time as sowing.
  • Check for insect pests - oversowing won’t kill them.
  • Oversowing is low cost, but the results depend on competition from existing pasture and weather conditions. You’ll be lucky if 10 percent of the viable seed establishes as seedlings.
Overdrilling or direct drilling

This is where new seed is put into an existing pasture with a drill fitted with coulters, discs or chisels.

Key points for success:
  • Graze off the old pasture as low as possible.
  • Use a pre-emergence weed spray if you expect weed problems.
  • Blanket-spray with a herbicide, such as glyphosate, to kill the pasture.
  • Band spraying (kills 40-60% of the pasture) can also be used.
  • Stock can graze a sprayed pasture without harm.
  • Consolidate after sowing with a Cambridge (ribbed) roller.
  • Chain harrows, then rolling, can also be used.
  • Spread fertiliser at sowing.
  • Usually better than oversowing, depending on existing pasture competition,
  • so graze to keep this low.
  • Spraying and drilling add greatly to the cost.
  • Avoid using a high seed rate - weak plants that don’t compete are usually the result.
  • Check for insect pests and slugs - overdrilling will not kill them.
Undersowing

Avoid using this term for pasture renovation - it causes confusion. It was used to sow pasture seeds into a growing cereal crop, which was thought to act as a “nurse crop”.

Cultivation or tillage
  • “Minimal tillage” - the pasture is broken up with disc harrows or grubber. It may look rough before drilling. The drill acts as another cultivation before finally light harrowing and rolling.
  • “Full tillage” is where the land is ploughed or rotovated, breaking up the existing pasture before cultivation and sowing.
Here are some general points:
  • This is the most expensive renovation method.
  • It has the greatest success.
  • Spraying out the pasture is strongly recommended.
  • Heavy grazing after spraying hastens death and rotting of the old pasture.
  • This method kills insect pests and slugs for a month or so.
  • Work in fertiliser for maximum benefit.
  • Seedbed should be fine and firm.
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