2017-07-26 

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Soil Assessment Key Prior to Autumn Reseeding

Think you’re a decent grassland manager? According to independent soil and grassland management consultant Chris Duller, the answer lies beneath the ground’s surface.

“There are times when soil has to come before grass. Soil before milk. Soil before everything,” Chris told 200 farmers at Germinal’s grassland management and reseeding open day on July 4, at Trefranck Farm in Cornwall. As farmers gear-up for late summer reseeding, Chris stressed the need to evaluate soils sooner rather than later.

Soil and grassland management consultant Chris Duller goes below ground to show farmers how compaction can impact negatively on grassland productivity.

Soil and grassland management consultant Chris Duller goes below ground to show farmers how compaction can impact negatively on grassland productivity.

Restrictions to root growth, water and air movement, combined with reduced soil biological activity within damaged soil can have significant impacts on grass growth, he said. According to him, soil with moderate damage can reduce yield up to 30 percent, not to mention setting up a more habitable environment for short rooting weeds like annual meadow grass.

Along with visual inspections of soil structure, Chris Duller stressed the importance of sending soil samples into labs for evaluation to check soil nutrient status.

“It’s going to cost you less than £15 per sample, but tell you exactly what nutrients are in your field and what it is lacking,” he explained. “Ideally, you really need to start sampling well in advance of reseeding, to allow time for remedial action.”

How to soil score

A few minutes and a decent spade is all it takes to score your own soil, Chris told open day participants as he turned over a scoop of soil to evaluate it. While Chris has assessments down to a fine art from years of experience in thousands of fields, he suggested grassland managers use the Healthy Grassland Soils’ 1-5 scoring guide to soil structure, which can be found in full at beefandlamb.ahdb.org.uk/assess-soil-structure/

Grassland managers with soil falling in the 1 and 2 range can sleep easy knowing their ground is in good condition. However, a score of 3 and above may, he said, require groundwork and strict management practices to repair soil structure. Actions that can be taken without the use of implements to preserve lays and minimise operation costs should first be considered.

“A lot of soil damage recovers on its own – particularly if there is earthworm activity, but it needs a bit of TLC,” Chris explained. “Because of this, where you’ve found soil damage, use yard muck instead of high rates of slurry on fields since ammonium in slurry can kill worms. It’d be like if you sat in a full bath of salt – just sucks the moisture out of them.”

Grazing system management, such as rotational grazing, back fencing, lower stocking rates, along with little and often soil nutrition, can all lead to soil structure rehabilitation.

“And no matter what happens, don’t graze livestock on a damaged field on a wet day,” he stressed, adding that this not only leads to further compaction but is likely to leave you with no other option than a reseed.

While a lot can be accomplished without implements, they are needed in areas with higher levels of damage.

“Mechanical methods can help to speed up natural recovery, but are often not needed across the whole field,” Chris said. “Depth of damage needs to be determined to find which practice is needed.”

In areas of the field where there is surface capping, use a soil aerator with spikes or knives up to 10cm deep. If it is compaction damage, use a sub-soiler or sward lifer from 10cm to 15cm. Sub-soilers can also be used for deeper tillage in plough pans, as can a mole plough in some situations.

“At the end of the day, it’s all about walking your fields,” Chris said. “You must evaluate your soil and be proactive in any problems there might be to maintain good soil structure.”

Healthy Grassland Soils’ Scoring System: 1 or 2 = Good, 3 = Moderate, 4 or 5 = Poor.

Score 1 – Sward is intact with few wheelings. Aggregates (soil particles) are small and crumble easily. Contains many roots, worms and has sweet, earthy smell.

Score 2 – Aggregates are easy to break apart, are rounded, and measure around 10mm. Smells earthy and worms are easily found.

Score 3 – Aggregates will be firmer and less porous, but still break apart. Soil will lack noticeable earthy smell and have less root distribution.

Score 4 – Aggregates will be upwards of 5cm and not break apart easily. Roots will be clustered in large pores, and worm channels will be found around aggregates. Signs of poor drainage can be identified by red or orange mottling and soil may smell of sulphur.

Score 5 – Compact aggregates are grey, around 10cm and difficult to break apart. Few roots will be found and remain mostly at the surface or clustered into large cracks and pores. A sulphur smell and red or orange mottling may be found.

Germinal

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