Farm Ireland

Monday 19 February 2018

Reseeding: Pros & Cons - The grass really is greener . . . with reseeding

Michael O'Donovan, Philip Creighton and Emer Kennedy

There is huge variation in grass dry matter production on Irish dairy farms, as much as 50pc between farms and 60pc within farms.

While there are different reasons behind this difference -- poor soil fertility, soil type, drainage issues and poor management -- the most obvious is the lack of perennial ryegrass within pastures.

There is now increased emphasis on increasing grass utilisation on dairy and beef farms.

However, it is difficult to utilise non-perennial ryegrass pastures. What's even more difficult to achieve is high animal performance from non-perennial ryegrass pastures.

Previous research has shown clear advantages in animal performance from ryegrass swards compared to old permanent pasture.

What level of reseeding is taking place on dairy farms

In 2009 Teagasc Moorepark surveyed a number of co-op suppliers (530 suppliers in total) from Kerry, Connacht Gold and Glanbia, and a number of discussion groups. The survey was grassland and reseeding based and posed 46 questions to the participants. A number of key findings on reseeding strategies were unearthed.

The five most important findings from the survey are:

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  • Regular reseeding took place on 50pc of participants' farms, 25pc reseed infrequently and 25pc never reseed
  • Of those reseeding, 50pc of participants reseed 2-4ha/year, 20pc less than 2ha/year
  • Autumn reseeding was the preferred time for 75pc of survey participants
  • Post-emergence spray was used on 50pc of farms
  • Farmers estimate cost of reseeding at €200/acre

Reseeding is crucial for grassland farmers

Perennial ryegrass is a high-quality feed and is nutrient responsive. The biggest limitation on grassland farms in Ireland is that our swards aren't perennial ryegrass dominated.

Recent research in Moorepark has shown old permanent pasture to be on average 3t DM/ha lower in DM production to perennial ryegrass swards and 25pc lower in nutrient responsiveness. Figure 1 shows the dry matter contribution across the grazing season of a 10pc perennial ryegrass sward compared to 100pc perennial ryegrass sward. The majority of the difference in DM yield between the two swards is accounted for up to mid-May. Swards with low levels of perennial ryegrass are nutrient inefficient, 25pc less than swards with high levels of perennial ryegrass; they have no role on farms and should be replaced.

If spring grazing is an objective, it will not be achieved with a 10pc perennial ryegrass pasture. This concurs with the findings of the survey, where farmers found greater early spring growth and higher quality pasture with reseeded swards. From an economic perspective, a low proportion of perennial ryegrass in the sward is costing dairy farmers €300/ha in loss of DM production during the growing season. In general, pastures with less than 65pc perennial ryegrass should be reseeded.

The aim of reseeding is to create swards that are:

  • Productive
  • Maintain high grass quality
  • Reduce silage requirement
  • Nutrient responsive - (+10kg DM per kg N)
  • Allow higher animal output - 8pc higher milk output per ha relative to permanent pasture
  • Increase the productive capacity of the farm (carry a higher stocking rate).

Spring reseeding

A major limitation of reseeding practice in Ireland is that reseeding is focused totally on the autumn. There is no doubt that autumn is the preferred time to reseed but this is mainly from a feed budget viewpoint.

In 2009 a study was carried out to investigate the impact of reseeding method in spring on DM production in the year of establishment. One pass and direct drilling were found to be the most productive. The most important aspect of this study was that the DM production from a spring reseed produced as much, if not more, grass than the control (old permanent pasture).

It is an encouraging result given that in 2009 it took 11 weeks for these reseeds to return to producing grass after initial spray off with Roundup. A delay in the cultivation of three weeks held up the cultivation process in early May. Establishing clover in a spring reseed is more reliable than autumn due to the stability of soil temperatures in late spring.

Turnaround time

When reseeding in spring the turnaround time for the pasture to return to production is faster than in autumn. Target turnaround time should be 60 days. Generally farmers are slow to reseed pastures because they view the non-productive period as being too long. The time that the sward is out of production can be minimised. Spring reseeding is more beneficial in terms of recovering the loss in DM production in the initial year (Figure 2). A major failing at farm level is to wait too long after spray off, cultivation can begin 7-10 days post spray off.

Reseeding cost

Reseeding is a costly but worthwhile investment (Table 1). Newly reseeded swards can be expected to last for 8-10 years or longer. Such swards will be required to sustain management changes to the dairy system over that time period. When looking at the full costs of reseeding, a range of different reseeding systems exist and some costs are lower on farms. The costs reported here are similar to those detailed by the survey participants throughout the country.

Irish Independent