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Improved Soil Health Brings Benefits on Heavy Land Farm - AAF

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Article from Agronomist and Arable Farmer – April 2018

When Cambridgeshire farmers Adrian Abblitt and son Charles decided to move away from the traditional plough-based system to control resistant black-grass, they never fully predicted the benefits it would have on soil health across the 445ha (1,100-acre) family farm.

Earthworm populations are noticeably higher and the heavy Hanslope series clay at Grange Farm near Sawtry is much better structured, which is improving natural drainage and allowing timelier field operations in autumn and spring.

“Soil is a lot firmer, without being compacted, so tractors aren’t sinking in to the depth of the plough as before. We get a better tilth, can drill around a month later than we used to in the autumn for black-grass control and can travel on land earlier in the spring,” says Adrian.

It was a visit to the National Black Grass Centre of Excellence at Brampton in 2009 that inspired Mr Abblitt’s decision to use shallow tillage to control RRR-resistant black-grass,  and working with Hutchinsons agronomist Simon Wilcox he has fine-tuned the system to benefit weed control and soil health.

Mr Ablitt now uses a 4m Cousins Surface Pro cultivator, which is the main cultivation ahead of all crops and has so far performed excellently.

“It moves soil consistently to a 50mm depth, won’t ride up over the ground and the packer-roller reconsolidates soil well. This all helps stimulate black-grass germination ahead of drilling and keep weed and volunteer seeds, moisture and organic matter in the top layer.”

While oilseed rape is sown with an 8m Dale drill around the end of August on fields free from black-grass, land destined for winter or spring cereals is left untouched until mid-September. Soil is moved once with the Surface cultivator to stimulate a black-grass flush which is sprayed off before drilling - usually with a 6m Weaving GD.

The good tilth and “table top-level” soil has knock-on benefits for crop establishment, slug control and improving the accuracy of subsequent fertiliser and spray applications.

Yields are benefitting too, with the rolling average wheat yield increasing slightly to 9.5t/ha and spring barley capable of 9-10t/ha.

Another notable benefit from shallow tillage is the reduction in nitrogen mineralisation compared with ploughing, Mr Wilcox adds. “Moving less soil means less oxidisation of soil nitrogen, which gives us slightly more control over grain quality with bagged nitrogen.”


Building Organic Matter

The retention of organic matter close to the surface and not disturbing soil to depth is key to improving soil health, says Mr Wilcox, who points out that organic matter levels at Grange Farm are already much higher than a typical heavy clay soil.

Some fields have up to 7% organic matter, which is a direct benefit from chopping crop residues and minimising soil movement. No additional organic manures are applied, and although compost was tried a few years ago, the quantities involved and logistics made it uneconomical.

Surface organic matter retention has significantly enhanced earthworm activity and plant rooting, which in turn aids natural structuring to create a “honeycomb” effect through the profile and a more resilient soil, Mr Wilcox says.

Visual field inspections reveal particularly strong populations of deep-burrowing worms, with one count of 50-100 middens/m2 (small piles of crop residue and worm casts over burrows) in a direct-drilled cereal crop after spring beans. There are also more beetles, spiders and beneficial insects such as ladybirds, he says.

Surface organic matter also acts as an insulation “blanket” in winter, allows soil to warm up quicker in spring, yet keeps it slightly cooler and aids moisture retention in summer, he adds.

Mr Abblitt pays close attention to residue management and has just purchased a new straw chopper for the Case combine to give a finer chop that speeds-up organic matter breakdown.

Further measures to protect soils

Soils are more resilient, but Mr Abblitt says it is still important to protect structure and improve drainage wherever possible. Measures include:

  • Using relatively small, light machinery (largest tractor is a 210hp Case)
  • Lowering tyre pressures (down to 1bar)
  • Running the largest tractor on dual wheels when drilling and cultivating
  • Front tracks fitted to the combine
  • Using “high flex” floatation tyres on trailers
  • Restricting machinery to the 30m tramlines at harvest - includes keeping the combine to headland tramline when opening fields
  • Using RTK guidance on all equipment to restrict wheelings to the same areas
  • Regular mole ploughing (every five years where required) and thorough maintenance of ditches and land drains.