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Thursday 8 December 2016

Irish farms have significant capacity to grow more grass

Nora O'Donovan

Published 13/05/2015 | 02:30

Kevin Lane of Ornua (formerly the Irish Dairy Board) with Gerard Killoran, from Bunninadden, Ballymote, Co Sligo, the Aurivo Milk Supplier of the Year 2015.
Kevin Lane of Ornua (formerly the Irish Dairy Board) with Gerard Killoran, from Bunninadden, Ballymote, Co Sligo, the Aurivo Milk Supplier of the Year 2015.

Teagasc now have a number of farmers from all over the country recording their weekly grass measurements on PastureBase Ireland. Results show there is a huge capacity on Irish farms to grow more grass and one important element of this is reseeding.

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Perennial ryegrass dominated swards produce on average 3t DM/ha/year more than old permanent pasture swards. Importantly, most of this additional growth occurs up to mid-May. Reseeded swards are also 25pc more responsive to nitrogen.

The increased profitability of the reseeded pasture will cover the cost in just over two years. This makes reseeding one of the most cost effective on-farm investments. However, the cost involved is significant, which makes it crucial that farmers investing in reseeding get the best possible result.

Spring is the ideal time of year for reseeding. These swards will have similar if not greater total herbage production in the year than the old permanent pasture. Soil temperatures are more stable than in the autumn giving the grass and clover seeds a better chance of germination and establishment. Post emergence spraying for weed control is usually very successful with more favourable weather conditions in summer.

Ideally choose where to reseed based on the paddock's performance over the full year. It can be hard to pick poor paddocks in May. Think back to those which were slower to respond in the spring or last autumn. Also note those where the quality is difficult to maintain as you go through the summer.

While ploughing is probably the most reliable method of reseeding, minimum cultivation techniques when completed correctly are equally effective. Choose a cultivation method that suits your farm.

A fine firm level seedbed allowing good seed/soil contact is essential. Avoid clumpy sods on the surface to ensure that seeds (especially white clover) are not buried too deep. Perennial ryegrass seeds sown to a depth of 2cm will have a germination rate of 94pc versus 68pc for those sown to 4cm. After sowing the seedbed should be rolled again to ensure good contact. This will also help to keep moisture in the soil.

Soil fertility

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Soil fertility is critical to maximising the performance and longevity of swards at farm level. Lime and phosphorus are particularly important for establishment. But they are equally important to ensure that the ryegrass varieties remain in the sward. There is no point in reseeding a field if it performs badly after a few years due to a lack of lime, P or K.

One of the easiest choices to get right or wrong when planning the reseed is the mix of seeds that are sown. The cost of the bag of seed is one of the least important aspects in the overall picture.

Use the recommended lists from the Department of Agriculture and the AFBI (Northern Ireland). These are cultivars evaluated in Ireland across years and sites.

Many mixes available have cultivars which are not on these lists. This means either they were tested and are not good enough to be included or have not been tested under Irish conditions.

The new Pasture Profit Index (PPI) can be described as the EBI for grass. It is available on the Teagasc and Department websites and makes it easier to select varieties most suitable for your farm, whether its silage or grazing.

The PPI quantifies the total economic merit (€/ha/year) of the individual varieties. Just like the EBI it comprises a number of sub-indices. Each sub-index is given an economic value. This indicates if a variety is above or below the average of all varieties for that particular trait. The four indices are seasonal dry matter yield, quality, silage and persistency. Within this, different economic values are assigned depending on the importance of the traits. For example spring dry matter production is valued four times higher than mid-season dry matter production.

Ensure you use 3kg of an individual cultivar for it to have a meaningful contribution, which means no more than three or four varieties in a grass mix. Make sure to sow enough seed (14kg/ac).

Decide, based on the soil type, how much tetraploid and diploid you want in the mix. Diploids are denser and more persistent which will give better ground cover but tetraploids are more palatable and will have higher overall production. Later heading varieties will hold better quality in a grazing mix, whereas intermediate varieties will suit better in silage mixes.

It is very disappointing to see new reseeds performing badly on farms. It takes a year for the new sward to establish. Therefore, you should ensure soil fertility, weed control and management of the reseed is very good for the year. Encourage tillering by grazing at a low cover and avoid any poaching.

Nora O'Donovan is a Teagasc advisor based in Tralee, Co Kerry.

nodonovan@ independent.ie

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