Cover crops – lessons learnt from recent years

“Cover crops play a key role in this by increasing the above ground diversity which in turn increases the soil biology, giving greater functional biodiversity.”

“Diversity is key particularly when it comes to cover crop mixtures,” she points out.

“Cover crops can be utilised to dry soil and provide structural restoration – a function rarely achieved throughout the soil profile by a single or pair of species.”

“When growing a mixture, growth is more regulated, robust and the combined plant health is improved, with more compact height and greener leaves.”

The integration of the right cover crops, in the right place and at the right time, means that the usual ‘monocrop’ rule book does not apply, says Miss Cannon.

“This is a key consideration with multispecies covers and means they are far from being the perceived harbinger of pests, but in truth, mixed species covers are highly beneficial.

“It is, when you stop to think about it, a frighteningly simple principle – increase diversity and spread the risk.”

Alice points out therefore the importance of multiple species within the cover crop. “This doesn’t mean one or two species within a crop, as the diversity is simply not there to gain the benefits.”

Her advice is that mixtures need to be carefully chosen with the correct advice to go alongside them in order to achieve maximum benefits and prevent mismanagement that can often result in doing more harm than good.

The first question you must ask is ‘why am I growing this cover crop’?

• Pumping water out
• Stabilising sands or silts
• Loosening compacted horizons
• Rotational diversity
• Nutrient building, capture and cycling
• Increasing functional organic matter
• Seedbed tilth and quality
• Increasing Carbon
• Feed, build and maintain soil biology
• Drilling on the green
• Provide grazing
• Weeks or months duration

She adds that none of the above are mutually exclusive. “A cover crop grown to improve soil structure will also store nutrition, stabilise the soil surface, most likely help suppress weed growth and increase soil carbon and biology.

“But having an aim is the first step. It helps to ensure the correct mix is chosen and correct management is followed for your soil type for you to achieve your goal.”

Miss Cannon recognises best laid plans for establishing cover crops can be impacted by environmental conditions.

“In recent summers, the lack of moisture in August has seen many covers left in the bag, or poor covers have resulted where drills pushed on. Like any crop, catch or cover crops need good seed to soil contact and adequate moisture to establish successfully.

“Drilling summer catch crops for eight weeks, or cover crops for over winter, must be done in good time if adequate growth is to be achieved. This means a dedicated drilling operation directly behind the combine in August rather than being a job tackled after harvest is complete.”

“Once September is upon us, only a few species can hope to provide useful levels of cover growth.

“Where soil is moist, or rains have fallen from mid-July onward, then the use of sprayer mounted Outcast spreader units can be utilised to apply seed in the standing crop pre-harvest. This is particularly helpful in Northern counties or Scotland where harvest may not actually start until late August.” This technique is, however, unreliable when dry.

“Early summer covers such as maxi Intercrop should not be drilled too early, ideally leave until June. Over eagerness in getting this in the ground before that will find the grower having to manage the biomass and potential seed return later in the year via topping,” Ms Cannon says.

“In soils of greater than 30% clay, it is recommended that the catch or cover is established using a degree of cultivation, as this cultivation is effectively the seedbed for the next cash crop. The cover crop is utilised to stabilise, protect and enhance this cultivation over time.”

• Use cover crops to help repair soils that are too wet to establish spring cropping as planned to improve them before drilling.
• Where early drilled spring crops or autumn sown cereals have resulted in grassweed infestation and are being sprayed off or whole cropped, use cover crops to maintain soil structure.
• Maxi Intercrop has been specifically designed for early summer sowing to manage soils prior to autumn cropping.
• Let the seedbed dry and undergo any remedial action before sowing a cover.