Earlier this week I attended a discussion group meeting in Munster, where issues around grass and silage were the main topics of business.

Teagasc Grass 10 leader John Maher told the meeting that over half of all farms recording grass covers in PatureBase towards the end of last week, had covers of less than 150kg DM/cow on the farm – or, in other words, were in a grass deficit.

John highlighted a number of possible reasons for the lower-than-normal growth rates, aside from the less than ideal weather. He says that some of the thinking could be to do with less nitrogen in the soil reserves compared to other years due to severe rainfall over autumn, winter and spring, and less chemical nitrogen applied this spring compared to other years.

“So we know the target is to have 100kg N/ha spread by 1 May, which is typically broken down into 88kg N/ha from chemical nitrogen and around 12kg N/ha from slurry. Based on around 88kg N/ha of chemical nitrogen applied to date, and using standard allowances, the expectation is that there would be another 120kg N/ha yet to be spread for June, July, August and September,” said John.

The assumption is that there is less power in the ground to drive growth compared to other years because of lower nitrogen reserves in the soil. He stressed the importance of counting backwards to see how much nitrogen has been applied on a paddock-by-paddock basis and adjusting future rates accordingly.

A lot of farmers were saying they are on the edge regarding allowances for both chemical nitrogen and phosphorus. Most would normally apply a compound fertiliser like 18:6:12+S in April or May on fields that don’t get slurry in early spring.

In response, John said that farmers need to ensure they are making better use of slurry and avoiding things like spreading slurry on soil P index four land, just because it’s convenient to the farm, when other fields might need it more, especially where the farm may not have a high P allowance.

John suggested that farmers need to be clever with slurry, in that not all slurry tanks on the farm will have the same level of P. He said that slurry from individual tanks should be tested for N, P and K, and the high P slurry applied to the lowest P fields. He also said that farmers should be soil sampling every year in order to identify a reduction in soil fertility early and thus increase their allowance for P. Making better use of soiled water and applying reductions to nitrogen on high clover swards will also increase the allowance of nitrogen available to other parts of the farm, he added.

Residuals

The group walked into the field that the cows on the host farm had just come out of the night before. The post-grazing residuals were a little higher than desired, but not bad. John Maher estimated that the post-grazing height in the paddock was 4.5cm, whereas the target is 4cm. About half of the group said they were grazing to the same height, while the other half said they were grazing tighter.

After a wet spring when a lot of damage was done, getting the cleanout right has been a big challenge. Some farmers said that asking the cows to correct a high residual now will lead to a drop in milk yield. However, John Maher said it all depends on the pre-grazing yield that the cows go into;

“You can go into covers of 1,300kg or 1,400kg DM/ha and graze to 4cm and not affect the cow. It has been a hard spring due to weather and delayed grazings, not getting a good cleanout in the first round and saying ‘okay, we’ll get it in the second round’, but that didn’t happen. So we have to correct it as best we can. I would like to do this with the cows as much as possible, within reason.

“There is some pain in this. However, you can’t force the cows to go hard into residuals every single day, but you can get them to do a job on a residual every second or third day to get it somewhat right. I admit the game has gone a little bit away from us and there is some level of correction that may have to be done by machines later on, but we have to strive to get it right,” he said.

This task will get harder as we move towards the end of May and the grass goes into reproductive stage, when the stem gets harder, thicker and longer.

Silage stocks

One of the big challenges faced by the farmers in the group now was around silage stocks. Like most farmers, the reserves have been used up this spring and because growth was lower than expected in early May, many had to go back in and graze some of the silage ground. Some of the farmers are facing winter feed deficits of 20% and are wondering what action they should take.

What to do

  • 1. Apply extra nitrogen now to grow more grass and convert that surplus grass to silage over the coming weeks. The response to nitrogen at this time of year is high, but the law of diminishing returns applies. Most would agree this is probably around the 1.5kg to 1.8kg N/ha/day rate on grass-only swards, which is 31kg to 38kg N/ha after a 21-day round. Not every farm will have an allowance for 10kg N/ha extra nitrogen. At €1/kg N and a response of 35kg DM per 1kg N, the cost of the extra grass grown will be 3c/kg DM. About 70% of this extra growth will be utilised as silage and with harvesting costs of about 6c/kg DM, the total cost per kg of silage from spreading extra nitrogen will be around 10c/kg DM for silage. The cost of balancing for P and K is not included.
  • 2. Another option is to grow maize silage either on-contract or on parts of the home farm. The advantage of maize is that is not too late to sow it and is a high-yielding, high-energy feed with yields of around 13t DM/ha without plastic. Including a land charge of €740/ha, this will cost €2,441/ha or 19c/kg DM to grow and harvest. If this is being purchased on-contract, a margin for the grower needs to be factored into the price. Fields for maize will likely be out of production until the following June.
  • 3. If land is available for second-cut silage, the cost of fertilising with 75kg N/ha, 17kg P/ha and 75kg K/ha will be around €185/ha, based on current fertiliser prices. If this land is costing say €200/ha (€80/acre) and harvesting costs €250/ha, then the total costs of growing the second-cut silage will be €635/ha. If the crop yields 4t DM/ha, then the cost will be 16c/kg DM.
  • 4. Buying-in straights to feed during the winter was also discussed. The likes of soya hulls or palm kernel are available currently for €175/t. At 90% dry matter this works out at €194/t DM, or 19c/kg DM. The difficulty with soya hulls is that it cannot be fed ad-lib and so ample feed space and a suitable method is needed.
  • 5. Reducing stocking rate is another option. For example, maiden heifers could be contract-reared between now and 1 October, which is 130 days. On average, over this period the heifers would eat 10kg of grass per day, or 1.3t DM. If contract-rearing costs say €1.40/day, the total cost will be €182/head. If say 70% of the saved grass was converted to silage the silage yield would be 900kg DM/heifer contract-reared for the summer. If harvesting costs 6c/kg DM then the total costs involved in this option would be €54 for silage harvesting and €182 for contract rearing, which is €236 to produce 900kg of silage, which is 26c/kg DM. If contract-rearing was €1/hd/day, then the cost of the silage would be 20c/kg DM. This option shows the benefit of off-loading surplus or non-essential stock for the summer months in order to boost silage reserves.

    • John Maher, Teagasc.

    In short

  • Grass growth rates have been poorer than normal, but growth is good now.
  • Farmers should back calculate how much nitrogen was applied and set future rates accordingly.
  • Target residual height is 4cm and cows will graze to this if pre-grazing yield is not too high.
  • Look into various options if short on winter feed.