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Andrew Wilson, Brickyard Farm, Slingsby, Yorkshire

Andrew talks about how he has adopted regenerative ag approaches to support positive improvements for his root crops using less inputs and saving on time and costs.

Machinery available / Residue management

Cover crops do not require specialist machinery to establish, and can be drilled or broadcast using standard farm equipment such as fertiliser spreaders.

There may, however, be benefit in using more ‘high tech’ equipment if available, where a good example would be employing an Avadex spreader to ensure more even distribution of different seed sizes/weights when broadcasting.

Not all cover crop species will be equally suited to broadcasting though, and higher seed rates  may also be beneficial to compensate for expected lower germination and increased seed predation when seeds are surface sown. Where possible, rolling is recommended after using either method to improve establishment and minimise losses.

(Image: Crimper Roller, Newcastle University)

To further promote good seed to soil contact with either method, attention should also be paid to ensuring good residue management, with cultivation assisting establishment where soils require it to receive seed well. This can also help in ensuring a clean seed bed, minimising any competition from weeds.

Even when all of the above is considered, cover crop establishment can still prove to be variable, and subject to the vagaries of the weather and the threat of pests and diseases, with slugs being the most significant issue. Whilst little can be done to guarantee sufficient rain to encourage establishment (though rolling may help retain moisture), slug control can be actioned as in any standard crop if the need arises.

As cover crops are often grown to lift or lock-up left-over nutrients, fertilisers are rarely needed, and are only considered in circumstances where specific outputs are desired, such as building soil organic matter through biomass generation. In these cases, care should always be taken to adhere to any general and local rules on application type and timing, where for specific nutrient management recommendations we’d suggest contacting a specialist seed supplier such as Kings.

With the above in mind, it is often sensible to keep cover crop establishment simple, especially when beginning to embark on cover cropping for the first time. Here, cheaper mixes applied with existing on-farm machinery options will reduce any losses should establishment be disappointing, with options to devote more time and resource to cover crops in later seasons as experience builds to inform choices.

Sowing rates

Whilst you should be able to access recommended sowing rates for commercial straights and mixes online, or by talking to your distributer, in some cases you may want to create a cover crop seed mix that cannot be purchased ‘off the shelf’ and that is bespoke to your needs.

In this instance, as long as you already know the recommended seed rate for each individual species if it was being sown alone, you can use a simple formula to calculate the rate for each species in a mix. This works to divide the individual species sowing rate by the number of species in the mix and can be calculated using the equation below:

Seed rate calculator – conversion tool | AHDB

If you are unsure of the individual seed rate for a species, we’d suggest contacting your preferred cover crop seed supplier for advice, where standard rates for the most common cover crop species are also provided as part of our cover crop selection.

(Image: Shutterstock)

Sowing times

As with any seed, cover crops will only do well if sown at appropriate times, when conditions are suitable for good establishment and subsequent plant growth. In the UK, this typically means that cover crops are sown as soon as possible after summer/autumn harvest, providing the warmth and daylength needed for germination and establishment, and the maximum possible growing period before temperatures fall to levels that will either arrest or terminate further development.

Although certain cover crop species are more suited to later sowing times than others, generally speaking earlier sowing improves performance and choice, even allowing inclusion of certain C4 species that may show beneficial traits (e.g. improved drought tolerance). Where early establishment is not possible, for example in more northern regions with later harvests, sowing into standing crops pre-harvest may help to extend cover crop growing periods, and can be assisted through machinery solutions.

(Image: Avadex, Yorkshire Agricultural Society)

Time to maturity and flowering are also potentially important considerations when reviewing sowing times. Some cover crop species, for example, will develop biomass and flower rapidly after sowing (e.g. buckwheat and mustards) whilst others will take longer (e.g. phacelia and vetches). In general, the former may perform better if sowing is delayed, allowing more rapid accumulation of biomass in a shorter timeframe.

Sowing depths

Just as different crops need to be sown at different depths, so too do different cover crops seeds. You will find suggested to help you match straights and mixes to the available sowing depth ranges of your machinery, where a value of 0 mm indicates suitability for broadcasting on the soil surface.

A shallower drilling depth is required for most cover crops species, ideally drilled with good seed to soil contact. On heavier soils, shallow (80mm) tilth creating tillage when establishing cover crops can prevent problems after cover crop termination in the following spring crop with drill slot opening.

(Image: Direct Drill, Newcastle University)

Problems with variable seed depth requirements are most likely to arise with diverse cover crop seed mixes, though machinery solutions can help to establish mixes where individual seed depth recommendations vary (e.g. broadcasting surface sown seed from the front of the tractor whilst drilling seeds at depth at the back, or using a combi-drill that can place seed at varying depths from independent hoppers).

When mixing cover crop seed within a single hopper, caution should be taken to minimise any effects of gravitational separation, where heavier seed will separate to the bottom of the hopper during transit, even if seeds were well mixed when added. Adding seed mixes to the hopper in smaller, well mixed batches, as opposed to a single bulk load, can help here. It’s also worth remembering when broadcasting that heavier seeds may travel further, though machinery solutions can help here too (e.g. by using an Avadex spreader instead of a standard spinning disk spreader).

Useful resources:

We have reviewed a selection of recommended resources for cover cropping, all of which were available online in various formats. Based on scoring these resources against 5 key criteria for content on cover crop establishment, we would recommend the following ‘top 4’ for further information on this topic:

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