How to maximise your farm’s spring or autumn reseed

Most reseeding is traditionally done in the autumn, but there are reasons to suggest why spring reseeds might be best. Noel Gowen, grassland and livestock consultant for Grasstec, explains how to make the most of reseeding work.

Traditionally, most grassland reseeding takes place in the autumn (August/September), with about one-third of drilling occurring in late spring (April/May).

There are positives and negatives to both approaches, but, on balance, Dr Gowen suggests that spring reseeding is the best option.  

Whatever the drill date, remember that time is needed to allow regrowth before grazing, he stresses.

A timeline of 65-75 days should be given between starting reseeding work and the grazing, including 10-12 days after swards have been sprayed off.

Dr Gowen says that with Irish costings around €300/acre (€741/ha) for reseeds and AHDB costs at ranging from £400-£700/ha, it Is important to make the most of your investment.

When done right, he says research shows swards dominated by perennial ryegrass can produce 3t/ha of DM more than old permanent pasture and are 25% more responsive to soil nutrients.

See also: Tips on assessing the health of your soil

Spring v autumn reseeding

 

Spring

Autumn

Positives

  • Reseeding at a time of highest grass growth
  • Less “other feeds” needed to compensate for the unavailable reseeded area
  • Subsequent summer conditions ideal for grazing reseed and weed control
  • No stem and seedhead production in the first season
  • Subsequent summer soil temperatures for clover establishment
  • Reseeding in August in high soil temperatures with rapid establishment
  • Little or no risk of drought conditions with autumn reseeding

Negatives

  • April weather window of opportunity for reseeding can be variable
  • Potential drought stress mid-summer in low rainfall areas
  • Deteriorating weather and soil conditions for grazing as the autumn progresses
  • Potential for high overwinter cover will reduce tillering
  • Limited window for post-emergence weed control

Soil fertility

For the benefits of reseeding to be optimised, soil fertility must be right – not only for establishment but also for subsequent growth through the year.

  • Essential to understand soil fertility status before reseeding
  • Soil test for P, K and pH at a minimum and for additional trace elements if deficiency is suspected.
  • Phosphorus is essential for root development. Phosphorus soil index should be level two on the UK system, with a typical application rate for reseeding of 30-40kg/ha.
  • Potassium soil index should also be at two, with a typical application rate at reseeding of 50-70kg/ha of K.
  • Don’t forget the value of slurry to supply these nutrients. Application of 3,000-4,000gal/acre pre-cultivation is adequate to supply nutrients for establishment.
  • Don’t compromise on lime requirement. Target soil pH of 6.3-6.5 for mineral soils or 5.5-6.0 for peat soils.
  • Nitrogen is the main element to drive grass growth. Apply about 40kg/ha of N at reseeding or on establishment of the grass tillers.

Choosing varieties

Between UK and Irish evaluation systems, there are a lot of perennial ryegrass varieties to choose from.

The AHDB’s recommended grass and clover list operates in England and Wales.

In Ireland, a useful extension to this process is via the Irish Pasture Profit Index, which compares the relative economic value of the varieties for a grazing system.

This index prioritises grasses with high digestibility and those who have higher growth potential in spring and autumn.

Most reseeding is carried out using a mixture of varieties as oppose to monocultures.

When putting a mixture together consider the following:

  • Is it for grazing or silage production?
    • Silage mixtures tend to be dominated by early and intermediate heading varieties
    • Grazing mixtures tend to be dominated by late heading varieties, which are in general slightly lower yielding but with better sward characteristics and high digestibility
  • Plan for a seeding rate of 30-35kg/ha
  • Three to four varieties per mixture
  • Keep the variety heading date variation less than seven days.
  • Take cognisance of disease resistance scores

Tetraploid vs diploid

Probably the most common question that arises when putting together a mixture is what ratio of diploid to tetraploid varieties to use.

Better to understand the differences between them before deciding.

Mixtures head to head

 

Diploid

Tetraploid

Positives

  • High tillering capacity
  • Higher ground cover, which will reduce poaching and damage in poor grazing conditions
  • Less weed and weed grass burden over time due to higher ground cover
  • Higher persistency and lifespan
  • On average higher yield of grass
  • Higher sugar content and higher intake characteristics
  • Easier to achieve residuals
  • Studies have shown higher cow performance from tetraploids compared to diploids

Negatives

  • On average, lower yielding than tetraploids
  • Lower tillering capacity
  • Poor ground cover
  • More prone to poaching and damage
  • Lower persistency

Most mixtures will have 30-50% tetraploid and the remainder diploid. It is clear that tetraploids have a positive contribution towards grass mixtures.

Their level of inclusion depends mainly on whether the soil paddocks are considered wet or dry.

If soils are wet then the amount of tetraploid should be reduced, and if they are dry then the amount of tetraploid is increased and in some cases can be 100%.

Hybrid and Italian ryegrasses are an alternative to perennials but more suited to silage systems.

They offer a much higher production capability but are lower in summer digestibility and are significantly less persistent, with only a two-to-four-year lifespan.

Method of cultivation

There are four main methods of cultivation and in general there is little difference in their effectiveness if they are done correctly, says Dr Gowen.

Consider keeping coulters high (6-7cm) above the soil to scatter seed, rather than sowing it in lines to cover the ground and help tillering. 

Cultivation dos and don’ts

 

Do

Don’t

Ploughing

Shallow plough and till to produce a fine, firm, level seed-bed

Plough deep – 20-22cm maximum is generally fine

Disc and sow

Graze or cut tight in advance. Disc with two to three passes to break clods

Drive too fast – for both discing and sowing

One-pass

Graze or cut tight in advance. Slow forward speed to allow the rotavator to prepare seed-bed, and allow the seed to scatter

Drive too fast leaving a cloddy, rough seed-bed. Sow in lines

Direct drill

Graze or cut tight in advance. Wait for ground to be moist

Use when the ground is very dry and hard – there will be little seed-soil contact

Tips for the first year

It is the management of the sward in its first year that is most important in ensuringit will last the 10 years with a high level of productivity.

There are some simple rules of thumb for management in the first year:

  1. First grazing at 2,200-2,500 kg/ha of DM pre-grazing cover
  2. Subsequent grazings at 2,600-2,800 kg/ha of DM
  3. Graze down to a low residual of <4cm or down to 1,500 kg/ha of DM
  4. Never allow a reseeded sward carry a high cover for a long period of time – this reduces tillering and allows weeds and weed grasses to germinate
  5. If it is a “silage paddock”, it is preferable to graze it for the first season
  6. Never poach or damage the sward