Low cost pasture renovation in high rainfall areas.

Thursday, May 09, 2024

Stock Jounral Article - March 2024

Author: Tim Prance, T Prance Rural Consulting, Victor Harbor

Before renovating any paddock, consider if it is possible to improve productivity by

  • correcting nutrient deficiencies.
  • correcting soil acidity.
  • controlling weeds using “spray-grazing” in winter or “spray-topping” in spring.

Also ask yourself why has the pasture and carrying capacity deteriorated?

  • increased acidity due to product removal, especially frequent hay cutting.
  • inadequate fertiliser applications.
  • seasonal factors such as late or patchy “breaks” or short springs.

A soil test is an essential starting point.

Soil acidity, along with deficiencies in phosphorus, sulphur and potassium should be corrected before renovating a run-down pasture. Weed issues such as fog grass and silver grass are often due to poor soil fertility.  

If your pasture has become grass dominant with barley, brome or silver grass the paddock should be cleaned the previous spring using an early silage cut or by spray topping/hay freezing or sown to a summer crop such as a fodder brassica or a forage sorghum/millet.

Pastures which are dominated by capeweed, geranium or thistles in early winter can be managed by maintaining ground cover in late summer/early autumn, introducing a vigorous grass (ryegrass or a cereal) in late autumn and spray grazing with a phenoxy herbicide in early winter, or a combination of all three methods.  

If a pasture is not weedy with grassy weeds, and only needs thickening up, it can be oversown (sod sown or direct drilled) before the break of the season with an annual or perennial ryegrass and sub clover pasture seed mix.

Before oversowing in autumn, the paddock should be grazed to remove dry growth (down to 1-2 cm height) but still maintaining 100% ground cover, and a disc/T boot/knife point seeder is used for seeding.

Soil disturbance must be minimised to minimise weed germination after seeding.

The keys to successful low-cost pasture oversowing are.

  • Dry sow early before the end of April
  • Good seed soil contact. This means sowing deep enough to cover the seed with 5-10mm soil for clovers and 20-40mm for cereals/ryegrass. To obtain enough soil tilth to adequately cover the pasture seed, the seeder may need to be set much deeper. Press wheels help to compact loose soil over the pasture seed.
  • Monitor depth of soil over the seed, not seeder depth. Most failures with pasture oversowing before the break are due to poor seed coverage. Deep sowing requires a reasonable opening rain for germination (20-25mm). Shallow sowing will result in a partial seed germination due to a false break.
  • Make sure pasture seeds fall into the seeding furrows and are not bouncing onto bare ground.
  • Oversowing before the break works best with cereals, ryegrass (annual and perennial) and clover (sub, balansa, persian, strawberry and white). Dry oversowing is rarely successful with phalaris or tall fescue.
  • Use a high seeding rate such as 10 kg/ha for sub clover and 5 kg/ha for small seeded clovers,15-25 kg/ha for ryegrass (depending on seed size – higher rate for tetraploid Italian ryegrass) and 80-120 kg/ha for cereals.

Fertiliser at seeding is not essential provided any serious deficiencies have been corrected before sowing.

Grazing should commence as soon as the pasture is established, which is 3-4 true leaf stage for clovers and 2-3 leaf stage for grasses. Early grazing is also essential to control weeds as no presowing/pre-emergent herbicides are used.

The advantage with this method is that pastures are not out of production for long periods, so graze early.

Dry oversowing is only successful in paddocks where grassy weeds are not a problem. If the pasture has become weedy, then grassy weeds should be controlled the previous year.

Failures will be due to:

  • Late seeding.
  • Poor seed soil contact
  • Weed competition especially annual grasses.
  • Insufficient grazing in the first year.
  • Over sowing slow establishing grasses, such as phalaris or tall fescue.