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Why is it that grass margins are usually in much better heart than the cropped land? Is there something
magical about grass? Field margins in many ways set the bar for soil health on your farm.
But is that as good as it can get? And do we need to go down to grass to achieve it?
“I believe the answer is no” writes Niels Corfield, crop advisor

We can go beyond the grass fallow and achieve good results in a short time frame. Because ultimately when cropping, we have more tools at our disposal. However, we have to employ those tools extensively, and thoroughly, if we’re going to actually see these results on our farms, in any reasonable period.

What are the tools that we have available to us? It’s just going no till, right? Well, basically, it’s the application of all the soil health principles. Mimicking the conditions we find under grass. That said, the acid test is in the soil condition. The good news is that you can actually see soil health. But what does healthy soil look like? Must it be lab tested? No, simply put, aggregation (crumb structure) is that measure. With that said what are the primary rationales for adopting soil health practices? Why should we, as farmers, advisors & land managers care? Are there any production benefits?

Improved soil health basically equates to better crumb structure that’s looser, easier to work and more absorbent. Certainly, the longer a ley is down for the better aggregated the soil becomes. So before we get into the detail, I want to put this in a global perspective. Ultimately, with 4 degrees of lockedin warming, coming down the line, business as usual is not an option. The warming we are dealing with now, as well as that coming means, for example, we can’t rely on rainfall to germinate spring crops, we need to do it with stored soil moisture (another reason not to till). Only improved soil health (crumb structure) can deliver this – so your disk drill can place the seed easily into a porous and moist seedbed.

When it comes to carbon sequestration, soil health practices, of which conservation agriculture (CA) is one example, is the only framework that can deliver the numbers we need to be hitting, under commercial conditions. That said, if we are really going to be able to make the case for soil-based production, we have to be demonstrating significant soil carbon results. Recent data from Brown’s Ranch recorded 96 tons per acre of carbon in the upper 48″ of soil, as compared to 10-35 tons for farms in the region. While there is much controversy around carbon auditing, and it probably isn’t a tool for day-to-day decision-making, these results represent a pretty high bar, and also an indication of what is possible.

Cover Crops

Over-winter cover crops (OWCCs) are the bread-and-butter of CA, they perform a vital role: preserving soil structure, holding onto nutrients, protecting soils etc. And in warm autumns they may actually do some soil building but generally speaking with soil/air temperatures being low and day lengths short, microbial activity is low, and root exudation is minimal. Also when temperatures are low, little or no N-fixation occurs, calling into question the rationale for buying those expensive legume seeds. Beyond these shortcomings, there’s limited species choice and slow growth.

Does this mean we shouldn’t bother with them? No. They still play a vital role in protecting soil & preserving structure. Though that said, where planted too late, or too thinly, OWCCs may not actually give sufficient cover either. But is there a way we can go further with our cover crops and get more pronounced results? Certainly. Spring sown or full season cover crop mixes open up the floodgates for diversity. And with it being in season, there’s plenty of warmth in the soil for optimal microbial activity (soil building), including nitrogen fixation by free living nitrogen fixing organisms, eg azotobacter. The diversity of plants means more specialist organisms should be being well fed through exudates.

But what about the cost of fancy mixes like these? Well, source seed from the feed merchant. A good starting point is bird seed mix. These tend to have at least the 8 species that are suggested as a minimum – getting that diversity lever up to where it wants to be. Just to reiterate the ideal is to have eight or more species from three or more of the functional groups: warm season/ cool season, grasses/broadleaves. The warm season plants are also the C4 plants, eg sunflower, millet, meaning more solar energy capture. Add to this any farm saved seed available. As well as this, include a tall straw cereal, like rye or population wheat – these may well be on the pricier end, so why not grow a strip or two of these as straights for combining for future mixes. 

Finally, all of these plants should be annuals as we then have more options for termination, including: rolling and trampling – so long as the planting is fully mature. It’s probably also worth leaving out any short-season inclusions, like: mustard, radish and even buckwheat, since they will shed viable seed long before this termination point, possibly volunteering in subsequent crops. At the end of the season obviously you will always have the option to spray off.

There’s certainly question marks around margin for in-season covers, probably the best return this would be to graze these covers, using low utilisation, ultra-high stock density (UHD) systems. By terminating in this fashion (along with rolling) and with having low utilisation there will be large pulses of root exudates produced during these grazing events. It’s exudates that contribute most directly to aggregation and soil organic matter. Ultimately the payback for root exudation is a steady supply of nutrients in a plant available form, that are free. 

Diversity and Cash Crops

Are we limited to soil building under cover crops? No, techniques like: band sowing, strip cropping, inter row planting/undersowing, crop mixtures, intercropping and relay cropping, are all indicated. Simply shifting from a monocrop to a bicrop doubles the diversity. Of these probably the most straightforward is strip cropping. The narrower the strips the better, to ensure the greatest interaction between the crop’s roots. Furthermore, the wider the spacing for the main crop the more a second planting is indicated. It would possible to undersow with a winter wheat (potentially bicropped with a legume) – making this more of a relay crop than an undersowing, and removing at least one spray pass. Basically, do whatever it takes to get diversity into your cash cropping, and to maintain a living root in the ground through more of the year.

Advice for getting started

On small acreages or one field (potentially, close to home), modify your operation to incorporate some of the following (ideally with a commitment for three years minimum):

Cover Crops

Plant a cover crop, properly, with high seed rate, early sowed, and with starter fertiliser. Where cover cropping already, try a diverse mix, 8 species or more, cheap/ farm saved seed. If you’re on the diverse over winter thing, then try it in season, ideally UHD grazed. Drill a cash crop into cover crop residues.

Cash Crops

Diversify the rotation, try a novel crop – maybe a seed crop Strip cropping: could be a header width, or just a drill width (that you then stripper header). Plant an intercrop, a two way mix, with that are co combined.

Niels Corfield is an independent advisor and educator specialising in soil health and regenerative agriculture. Check out his events page at the back of the magazine for upcoming courses or follow the QR Code to book places..

Written By Laura Barrera and first published on Agfuse.com

While soil health may be harder to quantify than benefits like biomass production or input savings, there are ways of measuring how cover crops are making a difference in your soil.

While there are numerous reasons for using cover crops, a primary one is improving soil health. In fact, it’s the one benefit most farmers using cover crops have experienced: In the most recent US Cover Crop Survey Annual Report, of those who rated the statement, “Using cover crops has improved soil health on my farm,” 86% agreed or strongly agreed.

The report notes that it’s interesting and heartening that “soil health reflects an embrace of a long-term, hard-toquantify benefit of cover crops, and that for the past two surveys, it has achieved the top spot by garnering 86% of the responses.”

1 – Reduced erosion

Protecting soil from wind and water erosion is a common reason growers begin using cover crops. The easiest way to monitor this benefit is simply by looking for signs that less erosion is occuring. Diane Stott, National Soil Health Specialist for the USDA NRCS’s Soil Health Division, says you can visibly notice less erosion by seeing how little runoff there is from a field after a rain or strong wings. If you have tile drainage, it should be relatively clear after a rain.

But to quantify a reduction in erosion, Stott says you place use stakes with measurement marks at the edge of your fields, preferably with one stake in a nearby field that’s not in cover crops for comparison. Over time, you can check those measurements on the stakes to see how little soil you’re losing, if any, compared to the fields that are bare.

Stott notes that it doesn’t take much for a significant amount of soil to be lost. In fact, if a field loses as little as ¼ of an inch of soil per acre, that’s 10 tons of topsoil gone. “I have seen fields where people who have been in cover crops for a number of years, compared to their neighbours who have not, and it’s frightening the amount of difference there is in the level of soil between the two,” Stott says.

2 – Less compaction

Another soil health benefit you should see after using cover crops is less compaction and deeper root penetration, especially if you’re seeding species like daikon radishes, which are known for growing a deep taproot. To measure soil compaction, you’ll need either a penetrometer, a soil probe or a steel rod, Stott says. If you’re looking for more precise measurements of your soil compaction, you’ll want to use a penetrometer. Which measures the soil’s compaction in pounds per square inch (psi).

In a Penn State Extension article written by soil scientist Sjeord Duiker, he recommends using the penetrometer when the whole profile is at field capacity, which is approximately 24 hours after a soaking rain. Spring is the best time of year for this, he says, because the whole profile will have been thoroughly moistened during the winter. He notes that if the soil is too wet or too dry, compaction could be under- or overestimated, respectively.

Some other things to consider when using the penetrometer are the tip options. In a YouTube video by University of Wisconsin Integrated Pest and Crop Management, soil scientist Francisco Arriaga explains that there is a ½-inch tip and ¾-inch tip. The ½-inch tip is generally used on soils that are harder, while the larger tip would be used for soils that are looser and have better structure

To take a soil compaction reading, Arriaga recommends first taking a reading in a fencerow or somewhere with the same soil type hasn’t had any traffic on it, which would give you a good comparison of the soil’s natural compaction. Push it in the soil and watch the gauge to see how much pressure is required to get through. The easier it is to push, the better your soil structure is. You can return to the same spots in the field year after year to perform this test and see how the cover crops are alleviating soil compaction. Stott says that if you’re seeding a cover crop mix that contains 30-40% radishes, you should see a difference after just one year. She also notes that covers are best at alleviating plow pans and compaction that was formed by equipment, livestock or tillage. Cover crops may not be able to alleviate diagnostic compacted layers that are natural in the soil.

3 – More earthworms

Earthworms are another indication of good soil health that you can measure, as they “need moist soils that have sufficient residue or organic matter for food,” writes Christina Currell, a water quantity educator for Michigan State University Extension. You can do earthworm counts to see if your populations are increasing by digging out a square foot of soil one foot deep, and counting the number of worms found, Currell says. To count for deep-burrowing worms, you could also level out the bottom of the hole and slowly pour a solution of 2 tablespoons of mustard powder dissolved in 2 litres of water, which will cause them to come to the surface within 5 minutes.

Currell points out that if earthworm counts are taken when the soil is dry, your number is likely to be lower, and populations are typically higher in areas with high organic matter. You should try to do your counts in a spot that’s a good representation of the field. She recommends doing the test several times during the growing season and to get an average count. Stott notes that if you’re located in a northern area, you shouldn’t be too worried if you don’t see too many earthworms.

“Understand that, especially in the northern states, earthworms are not indigenous,” she explains. “Most of them have been seeded. Anything that’s from a glaciated area, the earthworms are not native. So don’t worry if you don’t see any earthworms, it does not mean your soil is bad.” Instead, she suggests looking for other beneficial species and see if you notice an increase in populations as you continue cover cropping.

4 – Faster Water Infiltration

As cover crops help lower your erosion and compaction, while also increasing earthworm populations, your soil’s water infiltration rate should improve as well. To measure your infiltration rate, Stott recommends taking a No. 10 coffee can with both ends cut out and placing it in the soil. Pour two inches of water into the can and time how long it takes for the water to seep into the soil. The longer you use cover crops, the faster your water infiltration rate should be.

5 – Higher organic matter

Along with infiltrating water faster, cover crops should also help your soil’s waterholding capacity, as it increases the soil’s organic matter. According to the NRCS, organic matter holds 18-20 times its weight in water, which means 1% of organic matter in the top 6 inches of soil holds approximately 27,000 gallons of water per acre. Measuring organic matter just requires a soil test, but Stott warns that it’s going to take longer for growers to see a significant change in their organic matter percentages.

That doesn’t mean that soil organic matter isn’t increasing — just that it takes a while for the tests to detect those changes. Stott says you’re not going to see a significant change in your soil test values until there’s been at least a 0.3% change in the soil. If you’re in the Midwest, it’ll probably take 3-5 years to see your organic matter levels increase on your soil test results, she says, and if you’re in a drier region you may not see any significant changes for 5-10 years.

Because of how long it takes to see a change, Stott recommends taking a soil test before you start using cover crops to get a baseline number, but don’t test it again for another 5 years. In the meantime, look for qualitative changes to your soil for verification that your organic matter and soil health are improving.

6 – Better soil stability

One qualitative measure you can take to see how your soil health is improving is the Slake Test, also known as the Soil Stability Test.

The Slake Test, measures the stability of soil when exposed to rapid wetting, adding that soil stability serves as a “qualitative indicator of soil biological activity, energy flow and nutrient cycling.” To perform the Slake Test, you’ll need two glass jars, wire mesh that can be hooked onto the glass jars, and a chunk of soil from your fields, as well as some soil from another area that can serve as a comparison. The NRCS says this can be from a grassland, fencerow, or notilled field, if you’re not no-tilling. 

The Slake Test: This compares how soils hold together when wetted. The soil samples are held in a wire cage which is in the top part of a vertical jar of water. The jar stands for some hours and the test is to see how quickly the soil disapates in the water. The faster this happens, the less stable the soil. Low stability soils get lost through field drains and erode from the surface run off. For a visual on how the Slake Test is done, scan the QR Code below with soil scientist Ray Archuleta using it.

Another simpler qualitative measurement similar to the Slake Test is to spray the soil aggregates found clinging to roots. Stott says to place the aggregates in a dish and spray water on them. You’ll see if the aggregates hold together or if they fall apart.

You can continue performing these m e a s u re m e n t s over time to see how much your soil structure improves from cover crops.

7 – Visual Changes

Finally, one of the easiest tools for observing how your soil health is improving is the shovel. Stott recommends digging 1-2 feet deep in your soil to examine the color of it, how deep roots go and how soil aggregates are clinging to the plant roots. The color of your soil should be getting darker, she says, and you should see more soil aggregates near the soil surface. “They’ll start seeing a marked increase in that nice crumbly feel in their soil,” she explains, noting that this can occur as soon as the first season after using cover crops for growers in more humid regions”

If possible, it’s a good idea to do this before you start cover cropping, she says. She also recommends digging in a fencerow that you can compare to your field, so you get an idea of the condition of your soils and how close or different they are from their natural state. “You can learn so much that way and it’s a lot cheaper than sending things to the laboratory,” Stott says. To better track how these changes progress, take videos and photos so you have a way to compare how much your soil health improves.

If you want to know how healthy you are, there are a myriad of tests and tools to help you ‘quantify’ your
body condition – blood pressure, body mass index and cholesterol level, for example. Now there is a move to
develop ways to quantify the health of your soil, too.

In 2016, AHDB and BBRO funded the five-year Soil Biology and Soil Health Partnership. With its focus on soil health, one goal is to produce a toolkit to assist with its measurement and management. One of the first tasks was to review what could be measured and how practical it was to measure it. A broad range of indicators (physical, chemical and biological) has been assessed by the research team, including:

• Common indicators: pH, routine nutrients, bulk density and penetrometer resistance

• Less common indicators: visual evaluation of soil structure (VESS), soil organic matter/loss on ignition (LOI), respiration and earthworms

• New indicators: total nitrogen, microbial biomass carbon, potentially mineralisable nitrogen (PMN), DNA measures (e.g. of pathogens), nematodes and microarthropods

With so many soil attributes available for measurement, a simple way to bring the most relevant ones together was essential – enter the ‘soil health scorecard’. The team has identified threshold values associated with each attribute. When the results from the various field measurements are entered into the scorecard (currently an Excel spreadsheet), a traffic-light system flags up whether anything requires investigation (red), monitoring (yellow) or, if things are good, where no action is needed (green). To test the approach, a network of seven experimental sites has been established. The sites represent a range of soil management histories, soil types, soil organic matter additions, pH levels, drainage statuses/structures, climatic conditions and rotations (including grass leys, cereals, sugar beet and potato production).

A research case study, available on the AHDB website, has been developed for one of these sites. Located at Harper Adams University, it is a fascinating and unique long-term experimental site. Established in 1991, on a sandy-loam soil (‘Wick’ soil series), the site provides an extreme test for the prototype scorecard. It has a long history of repeat organic material additions (at recommended rates) in a predominantly arable rotation (cereals and potatoes). In fact, cumulative organic matter inputs range from 0 t/ha to 129 t/ha. Prior to the latest round of funding, the site had received support from a variety of sources: most recently, via the WRAP digestate and compost in agriculture (DC-Agri) field experiment (wrap.org.uk/content/digestate-andcompost-agriculture-dc-agri).

Five organic material treatments have been applied (Table 1). These include annual applications of cattle farmyard manure (FYM), cattle slurry, green compost, green/food compost and food-based digestate. There is also a control treatment, which has received manufactured fertiliser only. Fertiliser was also applied across treatments to ensure that nutrient supply did not limit crop growth. Initial measurements of topsoil physical, chemical and biological properties were made in October 2017 and a soil health scorecard was produced (Table 2).

In terms of soil organic matter (SOM), the thresholds set were based on those considered typical for the soil type and climate. Unsurprisingly, the control – which received no applications of organic matter – had a relatively low SOM content. The light-textured soils responded well to the application of organic materials, particularly bulky materials, such as FYM and green compost. Key nutrients were also measured – extractable phosphorus (P), potassium (K) and magnesium (Mg). Thresholds were based on values taken from AHDB Nutrient management guide (RB209). Levels of nutrients were relatively low in the control. Levels were higher across the organic matter treatments.

The soils at this site are inherently high in extractable P, and management strategies would need to consider this across all treatments, especially the FYM treatment. Visual Evaluation of Soil Structure (VESS) scores from the topsoil (top 30 cm) were also good at the site. VESS is a straightforward and quick way to test soil structure in three simple steps – soil removal, soil assessment and soil scoring. The soil quality score produced can help highlight where soil structure needs to be improved. Ideally, each distinct soil layer should be assessed separately, and management focused on the worst performing, ‘limiting’ layer. A score of 1 or 2 is good, a score of 3 is moderate and shows the soil requires monitoring, and a score of 4 and 5 indicates that management action is required.

Further information on VESS can be found, at: sruc.ac.uk/info/120625/ visual_evaluation_of_soil_structure

Counts of the number of earthworms (total number of adults and juveniles) showed that all treatments were associated with an active population – more than eight per pit is an ‘active’ population for arable or ley/arable soils. The application of bulky organic materials was also shown to improve topsoil bulk density (at 5–10 cm depth), from 1.4 g/cm3 on the control treatment to 1.3 g/cm3, where either FYM or green compost had been applied. The plan is to repeat the sampling process for three more years of arable cropping (winter wheat, potatoes and spring cereal). The impact of additional organic material applications on a wider range of soil quality indicators will also be investigated.

Other long-term sites in the network are also using the approach to determine the effect of crop rotation, pH, tillage and drainage status on soil health. 

The main strength of the scorecard is that it breaks down the challenge of improving soil health into manageable pieces. It can focus attention and guide management interventions to improve the overall health status of the soil. During the remainder of the partnership, the soil health scorecard will be refined and tested across the experimental sites, and in consultation with the project’s eight farmer research innovation groups. A set of indicators, which can be used to measure soil health in the field directly or indirectly (i.e. through sending samples away for analysis), will be developed by the project. Critically, the research will also improve understanding of the relationship between each component of soil health and crop yield.

One of the most exciting areas of activity is the development of more robust indicators, benchmarks and thresholds for biological properties. The 2018 annual report includes details of innovative developments in molecular biology that are yielding ways to measure the soil biological community, including the presence and distribution of soilborne pathogens.  

Information on the project can be accessed via ahdb.org.uk/greatsoils

AHDB Animal Scientist, Siwan Howatson, takes a closer look at the potential to incorporate livestock into the arable rotation through establishing a grass ley, while improving soil organic matter and increasing soil resilience.

Soil organic matter (SOM) is an essential element because it provides the soil with the resilience it needs to sustain a crop, through supplying nutrients and the right environment for growing crops by enhancing the physical, chemical and biological properties of the soil. Continuous arable cropping with little or no inputs of organic materials has led to a reduction in SOM on many arable soils. In some instances, arable land has SOM values below 1%, while an average of 4% is desirable.

Is grass the answer?

Incorporating temporary grass leys into arable rotations has the potential to enhance SOM levels. Improving SOM leads to increased moisture retention, better nutrient turnover and reduced risk of soil erosion. Grazing livestock on these temporary leys can also provide an extra advantage through the animal returns to the soil through manure, which is a good source of organic matter for the soil. AHDB research shows that adding amendments, such as farmyard manure or slurry achieves a yield benefit over and above the nutrient content of what you apply, with benefits seen after just two years.

Leys should be treated as an arable crop, with good soil structure and nutrient supply to ensure yields are maximised. The target for commercial grazing systems in the UK and Ireland is to use 10 t Dry Matter per hectare. There are many options for managing your grass leys, including grazing and silage production, and the type of ley should be chosen for its end purpose. See the table, which includes guidance on which type of grasses and clovers to use for your situation.

Managing your grass ley

A newly sown grass ley takes about 11 months to fully establish. During this time, it is important that the sward is encouraged to tiller as much as possible and is protected from any damage. An established perennial ryegrass sward typically contains 5,000–7,000 tillers/m2. The tillering process in new swards is strongly aided by grazing because it removes existing leaf and encourages a new generation of tillers to emerge at the base of the sward. Avoid using the new ley for cutting silage in the first six months, as this will not encourage tillering. Graze the new reseed as soon as it is not possible to pull the plants out of the ground by hand. This is usually at the two-leaf stage or when the grass has produced about 2,200–2,500 kg DM/ha.

Use sheep or youngstock for the first grazing, to minimise any potential soil compaction, particularly in wet conditions. Aim to graze autumn reseeds at about 6–8 cm down to 4 cm before the first winter to encourage tillering.

The need for multiple harvests, through cuts or grazing, means it is crucial to focus on utilisation, because this has an important impact on the cost of production. Utilisation can vary from less than 50% to more than 80% in well-managed systems. Improved utilisation is linked to investment in infrastructure (e.g fencing systems for grazed swards or machinery for cutting systems) and allocation of labour.

Black-grass bonus

If you are considering introducing a grass ley into your rotation, there is the opportunity for the cultural control of black-grass. It is important to remember that black-grass has low palatability for livestock, so the amount in the grass ley should be minimised. If the preceding arable crop had a high black-grass burden, ploughing is recommended to bury the seed below the germination depth. Delayed drilling of the ley in the autumn, until after the peak black-grass germination period, or drilling in the spring, will further reduce the number of blackgrass seeds germinating in the grass ley. 

In either case, cultivations should be used to prepare a sterile seedbed, which can be managed with further cultivation and glyphosate. Minimising soil disturbance when drilling the ley will minimise any blackgrass germination. There are no herbicide options for controlling black-grass in the ley if it is to be used for grazing or conserved herbage. Cutting or grazing a grass ley within an arable rotation is recommended for black-grass control to minimise seed return, and allows a rapid decline in the weed in the seed bank, and a reduction in the resistance pressure to current herbicides. When returning the grass ley to arable production, some viable blackgrass seed will still be in the soil. Soil disturbance will stimulate this seed to germinate. Consequently, spraying off the grass sward with glyphosate and direct drilling is likely to result in the lowest black-grass population in the first crop following the grass.

Cost considerations

As with all crops, understanding production costs is crucial to ensuring the enterprise is profitable. Calculating the cost of the ley is a three-stage process: firstly, working out costs on an area basis, including establishment, inputs, machinery and rents; secondly, estimating your yield and, thirdly, working out the costs for pence per kilogram of dry matter. Worked examples of this can be found in the AHDB Livestock and Arable Rotation guide.

Harder to quantify are the benefits to soil health through organic matter increases, grazing benefits and improvements in black-grass control for following crops. In the right situation, a grass ley may well be a good option to consider for your system and soils.

More information on grazing techniques, including measuring grass and infrastructure, such as electric fencing, can be found in the AHDB Better Returns Programme (BRP) manuals. You can read more on introducing livestock into arable rotation in our new guide, available at: cereals.ahdb.org.uk/livestock