Autumn grazing tips to optimise grass nutrient value in spring

To achieve optimal production from pasture, dairy farmers should avoid leaving long grass and feeding cows too much cake, according to expert advice.

“When you allow your grazing covers to get too long in the back end of the grazing season, it shades out the bottom of the plant, and then it won’t respond to grazing the same in the spring,” says grazing consultant Andre van Barneveld of Graise Consult.

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“If, on top of that, you’re feeding 3kg of cake, drop it down to 2kg – that will save you money and encourage the cows to graze properly.

“Think of it like asking a child coming home from a birthday party, fuelled on cake, to eat their vegetables,” he adds.

Autumn grazing management

Autumn management is crucial and includes hitting a pre-grazing cover of 3,000kg/ha of dry matter (DM), leaving a 1,500kg/ha DM residual and ensuring the base of the grass plant is green.

The most important thing for farmers to do is monitor, measure and make decisions on the situation in front of them, says Andre.

“You need to measure how much feed you have ahead of the winter and, if you’re short of feed, you must make decisions about whether to reduce the stock numbers or buy in feed,” he says.

Come spring, applying nutrients to grassland needs to go beyond the “this is how we’ve always done it” rhetoric, Andre stresses.

Simply pushing for maximum grass growth at the start of the season is not only inefficient, it also fails to produce the best possible pasture, he explains.

“It’s not about maximising how much grass you grow. It’s about optimising it. The higher you push your grass growth in the spring, the more at risk you are dropping into a trough later in the season, which will cost you in other ways,” he warns.

Andre van Barneveld © MAG/Anne Dunn

Spring soil temperatures

Many farmers apply nitrogen early in the year to encourage grass growth, yet this is only helpful if soil temperatures go above 8C, Andre points out.

Applying when there is a low response to that nitrogen can lead to “massive” losses.

“Evidence from trials has shown, for example, that in those conditions, nitrogen efficiency may be as low as 20% – which provides major cost-saving opportunities,” he says.

It is soil temperature that makes grass grow, not nitrogen, he adds, and only once it reaches the required temperature is the ammonia converted to plant-available nitrogen.

“Nitrogen is like a turbo on an engine. You need to get a certain amount of revs before the turbo kicks in. And if you’ve got low growth, you’ve got very little opportunity to accelerate it.”

The problem is compounded when grass is suddenly available in abundance, encouraging farmers to reduce grazing intervals to keep up with grass growth.

Quality over growth

Grass growth alone does not equal good-quality nutrition for the cows, Andre says. Ideally, rotations should be every 20 days to allow the grass to develop in such a way that it can utilise the nutrients from the soil and develop good root structure.

The conversation needs to move from just grass and nitrogen to nutrient density and having the right soil and pasture, he argues.

Many are still growing more grass than the cows can eat, and a high growth rate is a concern.

“I’ve seen people try to manage that with a 12- to 14-day rotation, and that’s the worst thing you can do. It’s bad for the root system and soil nutrient exchange, and the plant doesn’t have any substance,” he says.

Andre adds that farmers in some systems might grow less grass overall, but the value of that grass is much greater. He sees real benefit in mixed species and herbal leys to improve grazing quality.

“You don’t get the same peaks in growth, as legumes, clover and herbs are unlikely to grow at the same rate and they will give more resilience. Keeping them in the sward is the difficult thing,” he says.

© MAG/Anne Dunn

Nutrient value of slurry

When applying slurry, it is important to remember that the conversion process happens more efficiently than with artificial fertiliser. “Slurry has got other nutrients in there that really help your nitrogen use efficiency.

“If you apply slurry to that bottom wedge of your grazing platform, even if that’s mid-January or beginning of February, provided the ground conditions are right, it will work well,” Andre explains.

“[But] you need to minimise how much you waste and apply it to the bottom third of the wedge – that way, it won’t taint the grass and it’s got a long time to work before the cows come in.”

If soil conditions allow, every time cows graze a third of the farm, a slurry application should follow. “Your slurry might have 8-10kg of nitrogen/ha going on, which are really low rates, but that’s OK because you need to apply those nutrients at a rate that the plant can use,” he says.

With restrictions on application rates and dates in nitrate vulnerable zones, it is all the more important to understand a farm’s allowances.

This will ensure the most value is gained from those applications for maximum nutrient density.

Impact of growth rate on nutrient density

“Growing things too quickly, encouraged with too much fertiliser, impacts the nutrient density – not just in vegetables we humans eat, but also in grass,” Andre explains.

“We know that growing a good perennial ryegrass and feeding it with nitrogen grows you a lot of feed. But there’s a lot to be said for including clovers, herbs and other varieties in your swards, because it helps the rumen biology of the cow and is more efficient,” he says.

Stimulating high growth with nitrogen will only result in lowering the nutrient density of the plant. The reasons for this can be found in the roots, he says.

“The plant’s root system hasn’t had an opportunity to have that exchange of water-soluble carbohydrates feeding through the roots to the soil. And that soil microbiology feeding the plant back with nutrients from the soil to create nutrient density hasn’t happened.”

What is vital to overall cow health, Andre says, is always looking at grass first and establishing if it is meeting the nutritional needs of the animal.

“Often, we blame the cows for not getting in-calf at the right rates, and we’re getting more lameness than we should, but a lot of that comes down to nitrogen use and the nutrient density of what they’re consuming,” he says.

Andre van Barneveld was speaking at an AHDB event on optimising pasture performance for profit and sustainability, at Pant Farm, Llanddewi Brefi, Tregaron.