Over the course of the last 18 months, an experiment has been set up at Curtins Farm in Teagasc Moorepark looking at low-nitrogen-input systems.
The research farm has undergone significant change in that time.
The existing perennial ryegrass sward has been replaced, new hedgerows have been planted, parts of the farm are being re-wilded, field boundaries have been increased and a new ammonia-busting shelter belt has been planted around the farmyard.
Three sward types are being trialled and the herd is split into two groups based on breed, so there are six treatments in total. The three sward types are perennial ryegrass, perennial ryegrass with white clover and multispecies.
The perennial ryegrass sward with no clover is receiving 250kgN/ha per year while the nitrogen (N) application rate for the other two treatments is between 125kg and 150kgN/ha.
The EBI of the herd is €190 on average, with half the cows Holstein Friesian and the other half Jersey crossbred.
Performance of both breeds under the different swards is being analysed but so too are their milk characteristics such as micro and macro nutrient status, antioxidants, vitamins and amino acids, along with texture and sensory properties of the processed milk.
Teagasc researcher Brendan Horan is heading up the experiment along with PhD student Alann Jezequel from France and farm manager Caroline O’Sullivan. The current phase of the experiment will run for four years.
Last week, the Irish Farmers Journal visited the experiment along with members of the Mitchelstown discussion group – they were the first group in to visit Moorepark post-coronavirus restrictions and the first of many groups welcome to visit the new trial at Curtins.
Like farmers everywhere, the team at Curtins was struggling to manage quality in the swards after a number of weeks of very high growth rates.
While a significant proportion of the farm was closed for silage, pre-grazing yield was still on the high side and sward quality looked poor. However, post-grazing heights were within the acceptable range at between 4.5cm and 4.7cm.
The overall stocking rate on the farm is 2.75 cows/ha – there are no outside support blocks so the farm is set up to be self-sufficient.
Heifers are being reared elsewhere and come to the farm three months prior to calving. There are slightly fewer cows than planned in the study this year so the actual stocking rate is less than target.
The three different swards are managed more or less the same, save for differing nitrogen fertiliser rates.
Rotation length and pre- and post-grazing sward heights are similar for all three treatments. Soil fertility is excellent and equal among the three treatments. On average, soil pH is 6.8, phosphorus level is 12mg/l (soil index four), potassium level is 182mg/l (soil index four) and organic matter is very high at 9.53%.
Up to the end of May, fertiliser use was similar across the treatments at 110kgN/ha. By mid-June, the grass-only sward had an extra 29kgN/ha applied while the other treatments have about 40kgN/ha to spread between now and mid-September.
“Our plan is to spread nitrogen at low rates on the grass and clover and multispecies swards and to also skip a round or two if we can. All nitrogen is in the form of straight protected urea save for one round of ASN, which was spread in April to ensure all paddocks got their 14kg/ha of sulphur,” Brendan says.
Effectively, the trial is comparing one proven system (ryegrass and 250kgN/ha) with a relatively proven system (grass plus clover and 150kgN/ha) and with an altogether unproven system (multispecies). In this instance, unproven means not proven in an Irish dairy systems experiment with dairy cows. It is being grown successfully on many dairy farms with low levels of fertiliser input.
If they are to perform similar to the grass and 250kgN treatment, both the grass plus clover and the multispecies swards will be relying on the legumes (clover) to provide the nitrogen not supplied in chemical form. The legumes do this by fixing atmospheric nitrogen to the soil.
Importantly, they only do this when there are sufficient quantities of clover in the sward and at the moment, the researchers are disappointed with the amount of clover present.
There is an average of 4.4% clover in the grass clover swards and 7.2% clover in the multispecies sward on a dry matter basis. This is measured by taking a sample of the sward, drying it and then weighing the proportion of each species in the sward.
The researchers are disappointed with the level of clover, despite 1.5kg/acre of white clover seed being sown during a full reseed. They are contemplating over-sowing more clover into the grass and clover swards.
Eight species were included in the seed pack for the multispecies swards. The species and seed rates are outlined in Table 1.
Three grasses, three clovers and two herbs were sown. Grasses such as Timothy and meadow fescue were sown for their rooting depth and winter hardiness. The two herbs are plantain and chicory. At this stage, approximately one year after sowing, chicory levels are low.
“Chicory was the first to emerge and it got off to a great start and provided plenty of feed in the first year, when the other species were only getting going. It does seem to be dying out quickly but this is something we were expecting based on other people’s experience.
“So, long term, I’m not sure what it’s going to contribute but it might still have a role to play in suppressing weeds and providing high-quality feed early in the sward’s life,” Brendan says.
He is more confident about plantain. “It seems to be persisting well, with many paddocks at around 14% plantain. It’s native and we see it growing naturally in hedgerows so that gives me confidence.
“It’s seen as an important plant because it has been shown to reduce nitrate losses through increasing urine production but with a decreased concentration of nitrogen in the urine.
“It’s also been shown that when cows eat plantain, they partition more excess nitrogen towards milk and dung and less to urine. This is important because on free-draining soils, urine patches are the main source of N loss.”
Current performance is outlined in Table 2.
Pasture growth has been similar across all three treatments so far. In terms of milk solids, the cows on the multispecies swards have produced approximately 10kg more milk solids per cow so far this year compared to the grass-only treatment. The researchers are at pains to point out that it will be three or four years into the experiment before definitive conclusions can be drawn as background nitrogen will still be having an effect.
Since 1965, Curtins Farm at Teagasc Moorepark has been home to dairy systems research. Most research experiments are focused on components – if you do X, what happens to Y?
With systems research you get the whole picture, including unintended consequences. For this reason, systems research is very important.
For most of the last 55 years, the research experiments at Curtins have been geared towards identifying systems of dairy farming that will maximise profit, such as genetics, feed rates, stocking rate, etc.
In more recent years the effects of stocking rate on water quality have been analysed. The results of which showed no deterioration in water quality as stocking rate increased and when the level of inputs remained static.
A new shelter belt has been planted around the farmyard at Curtins. This is designed to give shelter to the farmyard but also to reduce ammonia emissions.
Native deciduous trees have been planted to the southwest while native coniferous trees have been planted to the northeast of the farm. Brendan Horan explained that by slowing the wind speed across the farm, ammonia emissions from slurry stores and housing will be reduced and that the row of coniferous trees will slow down the wind and any ammonia emissions picked up by the wind should drop, thus preventing them from being deposited elsewhere on sensitive sites.
“It’s a long-term project. It won’t make any difference for the next 10 or 15 years because the trees will be too small but we have to start sometime,” Brendan says.