Livestock were once commonplace on most farms, but over the decades as businesses have centred their attention on one sector, many arable enterprises have lost the power of the golden hoof.
However, as the focus turns to soil health, livestock is making its way back into rotations.
Widening the rotation, additional income and providing opportunities to work with local graziers or new entrants are well known benefits of livestock, but what is it that is so good for soil biology?
Joel Williams, soil health educator at Integrated Soils says: “Animals, particularly ruminants, are excellent recycling mechanisms.
“Materials like straw and stubble provide soil benefits like cover and protection, but they can take some time to break down. They’re rich in lignin and have a wide carbon-to-nitrogen ratio.”
This high carbon:nitrogen ratio means they may be less efficiently broken down by soil microbes.
“By giving it to a ruminant to process, it turns it into a very valuable manure and when that manure comes back down into the soil, that crop residue has
been transformed into something a lot more palatable to the microbes and various organisms in the soil. You’re providing this element of carbon and nutrient upcycling.”
The carbon cycling, decomposition process is also kick-started by the trampling of the ‘golden hoof’ as it mixes residues into the soil.
Mr Williams adds: “A little bit of disturbance can be a good thing. In studies looking at animal exclusion and inclusion, where animals are present, more of the carbon residue gets incorporated into the soil, which ultimately leads to greater building of soil organic matter.”
Opportunities to widen the rotation with break crops such as grass or herbal leys are also highly beneficial to soil health. In arable scenarios, when soil is moved or disturbed, carbon is oxidised. The introduction of a perennial crop such as grass means cultivations are eliminated and the ley itself inputs organic matter through its roots, residues and manure from any grazing stock.
Dr Lizzie Sagoo, principal soil scientist at ADAS, says: “Putting arable land to grass is probably the quickest way to increase your organic matter.”
Recent work as part of an AHDB Beef and Lamb project measured a statistically significant increase in organic matter on clay loam soils at Dyson Farming’s Norwood Farm, Somerset, after a three-year grass/clover ley.
Organic matter content increased from a mean of 7.8% to 8.1%, equivalent to an increase of six tonnes per hectare of organic matter in the top 15cm of soil.
“Organic matter underpins soil function, so there will be knock-on benefits in terms of soil structure and soil biology. At Norwood we also saw earthworm
numbers rise,” says Dr Sagoo.
Cover crops are often the stepping stone for the integration of livestock, however, the jury is still out on whether grazed or ungrazed cover crops are better for soil health, says Dr Sagoo.
“From a farmer point of view, the key benefit of grazing a cover crop is economic return on investment. If you graze it, you’re not creating more carbon, you’re
just changing its form from green matter to manure. The primary thing is the use of cover crops is great for soil health and if you can get an economic return from grazing, that’s brilliant. Just bear in mind not creating a new problem with soil compaction and poaching from the livestock.”
Mr Williams says he would lean towards grazing a cover crop because it could act as a useful tool for cover crop termination and help to reduce glyphosate or other herbicide use and benefit soil biology.
“Leaving residues on the surface is still important for that mulchy layer in a country like the UK, which can have very high rainfall, wet winters and high
“Keeping those cover crop residues on the surface is, I would argue, very beneficial. However, I would lean towards the use of livestock, because grazing the residues helps to convert plant material for the soil biology.
“It’s not just about the cow, but the how. Livestock can be damaging if overgrazing or poaching occurs but, if managed correctly, can be very beneficial.”
However, regardless of whether the cover is grazed or not, Mr Williams believes that of the five soil health principles that underpin regenerative agriculture, maintaining living roots is the most beneficial.
“If we look at emerging evidence on soil biology, soil organic matter formation and how to nurture and foster these processes, it’s very clear the root systems of plants, those living roots and root exudates, are absolutely critical to driving soil biology and so many soil functions. There’s a strong body of evidence building on how important these roots are.
“The use of more diverse systems such as cover crops, intercropping or companion cropping in arable rotations, mixed species leys or diverse pastures creates a diversity of root systems and exudates and there are a lot of benefits in terms of soil functionality.
“We love to debate about cultivation, but if you were doing some tillage, one of the quickest ways to repair [the impact of] that is with living roots. With exudates rapidly pumping out, those root systems will rapidly reglue the soil and improve structure very quickly.”
For those that rid their land of animals for good reason and do not want to return to the world of livestock, organic manures also carry much value.
Mr Williams says: “Artificial fertiliser and manure both contain nutrients, but the key difference is manure and composts are organic amendments. They are carbonbased fertilisers and have carbon embedded within them compared to mineral fertilisers which are typically just the nutrients. It might sound a minor detail, but that carbon is really important to stabilise and hold on to some of those nutrients.”
This carbon acts like a sponge, providing more of a slow-release mechanism compared to inorganic fertilisers.
“They can have a fraction of nutrients that are instant release, but also a fraction that are more sustained release. Carbon is also an important food source for soil biology and feeds the various microlife, insects and earthworms.
“The nutrients embedded in manure are more diverse, so it’s a more complete fertiliser with macro and micronutrients, giving you a more broadspectrum
“The only downside is the amount of various nutrients are lower, leading to additional bulk handling and spreading costs.”
The recent clarification of the interpretation of Rule 1 of the Farming Rules for Water by the Environment Agency (EA) jeopardises access to this valuable resource for many farmers.
Dr Sagoo says: “Organic manures are not a waste product to dispose of, they’re a resource to utilise well. They contain nutrients and organic matter which is critical to soil health. We should be looking at strategies to support farmers to maximise the value of those organic materials and get them back on the land.”
This means getting as much of the nutrient content into the crop as possible and minimising losses to the environment.
“We need to distinguish between high and low readily available N materials.
“Slurry, digestate and poultry manure are all high in readily available N and can supply a significant proportion of crop N demand. Therefore, we should
aim to apply in spring when the crop is actively growing and can take up the N.
“In contrast, materials like compost, biosolids and farmyard manure are low in readily available N and the risk of leaching from these materials is much lower. Most of these bulky organic materials are applied in autumn when soils are dry and able to take the weight of heavy machinery, meaning they can be incorporated before establishment of the next crop.
“Many farms are going to struggle to move from autumn to spring applications for these materials. They may have a limited area of spring cropping to spread to and it is much harder to apply these bulky materials accurately and evenly to a growing crop without damaging it. Farmers on heavier land may also be concerned about potential soil compaction from spring applications when the soils are generally wetter.
“It would be a huge shame if we end up incinerating some of these materials because we’ve limited the land bank available for application. We also need to consider ammonia emissions and phosphorus losses.”
This comes as an impact assessment, commissioned by AHDB and carried out by ADAS to evaluate the clarification, found that although the rules could reduce
nitrate leaching losses by 60%, they could increase ammonia emission by 10% and P loss by 30%.
To hear more about integrating livestock into thearable rotation, tune into the Crop it Like it’s Hot podcast at croptecshow.com/crop-it-likeits-hot-podcast