Soil health focus at Cereals 2017

Farmers, technical experts, agronomists and industry leaders descended on Boothby Graffoe in Lincolnshire in mid-June to attend Cereals 2017. The 64ha site comprised technical and trade stands, machinery demonstrations, conferences, crop plots and the Syngenta Sprays & Sprayers arena.

This year was the 40th anniversary of Cereals and nearly 500 exhibitors showcased the latest innovations in arable technology, soil husbandry, crop agronomy, farm management software and crop varieties.

Those who travel to Cereals will know that this is a big show and we intend to bring a number of reports over the next few weeks. This week, we begin with the increasing focus on soil health and plant root systems.

Addressing and improving soil health has received increased focus in the UK following the effects of decades of poor management on tillage soils.

Improving soil health played a big role in this year’s event once again. Activities ranged from an informative soil pit to novel methods of assessing soil health.

The soil pit

The soil pit almost doubled in size this year (20m long and 1.2m deep) due to the ever-increasing interest in the subject.

The objective was to give a worm’s-eye view of common problems relating to soil structure and to show the differing root structures of cereal and cover crops.

The pit also aimed to show the important role that earthworms play in incorporating organic matter and improving soil structure.

Dr Lydia Smith, head of the innovation farm in NIAB, explained why understanding crop rooting structure and soil management are so important for root growth.

In the pit, I could see that the thin fibrous roots under winter oat and winter wheat plants penetrated through zone A (topsoil) and zone B (subsoil).

However, penetration stopped when they reached the parent material, which was a chalky bedrock at 60cm depth.

Dr Smith emphasised that these roots could not have penetrated to this depth if there was compaction present. The roots under spring oats and spring wheat were much shallower by comparison, but these had still penetrated to a depth of 40cm.

One of the very clear messages from the pit was the role cover crops play in combatting compaction and assisting in the repair of soil structure.

Like in Ireland, many UK tillage soils have suffered the effects of decades of mechanical inversion, which created pans and contributed to the depletion of organic matter.

Cover crops

Dr Smith maintains that the inclusion of cover crops in cropping systems can play an important role in improving soil structure. The deep rooting structures of legumes, such as vetch, assist in incorporating organic matter deep into the soil horizons, open up soil pans and provide a food source for soil microbes. Where compaction is a significant issue, UK farmers continue to include tillage radish in their mixes. Its thick taproot could be seen penetrating zones A and B in the pit.

Importance of earthworms

Dr Smith stressed the importance of a vibrant earthworm population in all soil zones. The burrows and middens created by the worms could clearly be seen in the walls of the pit. Worms help incorporate organic matter throughout the soil layers. The food supplied by cover crops encourages earthworm populations to develop and grow within the soil profile.

Plough has a place

The crops surrounding the soil pit were established using minimum tillage. Minimum disturbance of the soil in a managed programme can contribute significantly to improving soil structure, but ploughing also has a role. Results from the sustainability trial in arable rotations (Star) project, which was initiated in autumn 2005, showed that ploughing has an important role in preventing the build-up of grassweeds and minimising pathogen carryover. Dr Smith emphasised the need to plough occasionally, if circumstances dictate, even where min-till is being practiced to help improve soil structure.

The underpants test

The sight of semi-decayed, soil-stained underwear hanging from a clothes line certainly made for an eye-catching display. Participants in AHDB’s monitor farm programme have been burying cotton underpants across their farms to provide a measure of the health of their soils.

When the underpants are dug up, their condition reveals the level of soil microbial activity within that soil and can be used to help show areas where soil health needs to be improved.

The results indicated that in fields where low soil disturbance was practiced and cover crops grown, the buried underpants had significantly decayed. This indicated a high soil microbial activity.

The pants had remained virtually intact in the fields which practiced conventional plough-based tillage. While microbes are not the sole indicator of soil health, they do play a vital role in the overall soil ecosystem.

Do your own underpants test

To till or not to till

It is widely accepted that conventional plough-based systems can have a detrimental effect on earthworm populations. Switching to non-inversion establishment systems such as min-till or direct drilling, while not always practical due to soil type and climate, can improve soil structure, increase earthworm populations and ultimately improve soil health. But do these strategies actually help?

A research project on a clay loam soil in Bedfordshire is being conducted by Rothamsted Research to answer this question. The research, headed up by Dr Jackie Stroud, is examining the best approach for zero tillage conversions on degraded soils through residue management techniques, undersowing legumes and restocking deep earthworm populations.

Earthworms can be classified into three broad classes based on where they live:

We will watch this research with interest. Increasing earthworm populations should help to reduce establishment costs while improving the state of our tillage fields.

The picture on the right is an X-ray taken of the container on the left which contains soil and one deep soil-dwelling earthworm. The yellow tracks in the right are a series of burrows created by the earthworm.

Assess your own earthworm populations

A quick count of the number of earthworm middens on the surface can be used to assess earthworm populations in your field. Middens are the piles (10cm) of surface litter (straw, grass, leaves) that have been dragged back to the burrow entrance at night by deep-burrowing earthworms. Count the number of such middens in 1m2. These should typically range from 0 (locally extinct) to 30, depending on soil management practices.

Another simple assessment is to count the number of earthworms in a spade-full of soil. As a rough guide, 13 to 14 earthworms per spade-full indicates a healthy population.

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