Sowing the seeds of grassland efficiency
With Teagasc research showing that some sward varieties are costing farmers €300/h per annum in reduced efficiency, now is the time to look at investing in autumn reseeding
Less than 2pc of Ireland's grassland area is reseeded annually despite grass being our dominant feed source, recent research has found.
And Teagasc researchers have identified that swards with low perennial ryegrass content are costing farmers up to €300/ha/year due to reduced dry matter (DM) production and reduced efficacy of nitrogen (N).
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However, reseeding costs approximately €750/ha and making sure the proper establishment of the new lay is vital to get value for money.
At a recent Teagasc/Aurivo farm walk in Roscommon, Mary McEvoy of Germinal Seeds stressed that timing is absolutely crucial with autumn reseeds.
"Now is the time to be thinking about what fields you are going to target and you should be aiming to have the seed in the ground by the first week of September after that conditions can go against us very quickly," she advised.
For many farmers, autumn reseeding may make sense from a feed budget perspective. However, there are challenges with soil conditions deteriorating as autumn progresses, lower soil temperatures can reduce seed germination, and variable weather conditions can curtail the opportunity to apply post-emergence spray and to graze the new sward.
Selecting your seed
According to McEvoy, the most important thing from a farmer's perspective is that he/she is using the seed from the recommended list and Teagasc's Pasture Profit Index (PPI) when selecting grass varieties for reseeding.
The PPI was introduced to the Irish grassland industry in 2013 and sets out, in economic terms, the agronomic differences in traits between grass varieties to allow farmers to select the most appropriate varieties for their farm.
It allows farmers to identify the grass varieties which provide the most significant economic contribution to a ruminant grazing/silage in their system. The key traits in the PPI are seasonal DM yield (spring, summer and autumn), grass quality, silage yield and persistency
"There are an awful lot of varieties that go through the testing system every year, and there is a reason that many don't make the list. They're not good enough, and they're not better than the varieties on the list.
"The Pasture Profit Index is like an EBI for grass varieties," McEvoy stressed. Among the most critical traits examined by the index is 'quality' which is a key driver of the palatability of the sward.
"With higher quality swards you will get higher intakes and better animal performance.
"Lower quality grasses will be higher in fibre, which will lead to quicker rumen fill. The rumen filling quicker means the cow will not be able to eat as much of it. Eating less of a lower quality feed will impact performance.
"Farmers must focus on varieties that are delivering on the quality traits," she said.
The performance of grass varieties as silage crops is also an important trait.
McEvoy said that farmers should make sure that the mean heading date in the mixture is not heading earlier than their planned first cut silage date.
"If the heading date is May 20 and you're not cutting till the 25th, that sward will have turned reproductive. It will have put up stem and seed head, and the quality will have deteriorated. If your cutting around the end of May you want a variety heading out around June 1.
"Matching heading date with the cutting date is critical," she explained.
Ireland has the perfect climate for growing grass during the summer, McEvoy told farmers stressing that there's no benefit to farmers from sowing varieties that give more grass in the mid-season period.
"Most of you are looking to get out in late February or early March so identify the grasses that can deliver more in the spring and grow longer into the autumn.
"Keeping animals at grass longer will reduce your demand for silage and concentrate.
"We are all well able to grow grass in the mid-season period. If we can grow more grass in the shoulders of the year, that's what's going to leave more money behind," she said.
McEvoy explained that 'persistency' is another hugely important trait. She pointed out that what farmers sow today they want to last for 8-10 years on their farm. The biggest driver of persistency on farms is soil fertility.
"If soil fertility isn't right none of these grass varieties will last three years never mind 10 years.
"If you have an issue with soil fertility, fix that before you invest in reseeding because that is where you'll get your greatest return."
McEvoy said the optimum grass sward has the right balance of both diploids and tetraploid varieties in the mix.
The diploids group bring the density to the sward, acting as a carpet underneath the animal, which helps minimise the risk of poaching.
Tetraploids are more upright in their growth habit. They are larger leaves and generally higher in quality and more palatable to animals.
"The goal is a sufficiently dense sward but high enough in quality and palatability that the animal can go in graze it and perform well on it.
"Depending on your soil type the optimum balance of diploid and tetraploid is going to vary," she said.
Farmers reseeding very heavy ground want more density to minimise the risk of poaching and would, therefore, select higher levels of diploids in the mix, she said.
"If you have very dry ground and you are confident you are going to be able to manage it, you could go up to 50pc tetraploid," the Teagasc specialist maintained.
"However, with tetraploid swards, you need to be getting into them at the right time and grazing them out.
"We have this perception that the thicker the sward, the better the sward. However, thicker swards are losing in terms of quality, so they are going to be less palatable and harder to graze out," she said.
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