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Direct drills put to the test in cover crop demo – Arable Farming

With cover cropping and direct drilling increasing in popularity, growers in Yorkshire recently compared machines across a range of cover mixes. Paul Spackman reports ...

When it comes to deciding which drill to buy or cover crop to sow, there is clearly no one-size-fits-all answer. Each farm, field and soil is different and everyone has their own budget and preferred brand.

The Hutchinsons drill demonstration at Grange Farm, North Frodingham, Driffield, was never designed to find the ‘best’ direct drill, but to highlight some factors growers should consider before investing in a new machine or putting a cover crop in the ground.

Nine direct drills from different manufacturers have been demonstrated at the site this season, sowing spring wheat into various cover crop mixes, providing growers with an insight into the features of each machine and the merits of key cover cropping options.

The 10-hectare field, previously in winter wheat with straw baled after last harvest, was divided into five 2ha strips of different cover crops. These included the MaxiRooter mix (sown at 12.5kg/ha), MaxiCover (4kg/ha) + oats (30kg/ha), MaxiCover at standard seed rate (12.5kg/ha) and an unsown stubble.

Cover crops were all direct drilled with the farm’s Amazone Cayena on August 30 last year and then sprayed off with 1000g/ha of glyphosate in late January. Five weeks later, the demonstration drills were brought in from local dealers to sow Cochise spring wheat at an open day for growers on March 3. Wet weather prior to drilling created some challenging conditions for all machines on the medium-bodied soil.

Crop assessments and plant counts were taken during spring and farmers were invited back to the site in June to view some of the findings with Hutchinsons agronomist Ben Jagger and colleague Dick Neale.

Plant counts revealed some variations in establishment of the spring wheat crop, which was sown at 450 seed/sq.m (200kg/ha).

Generally, the disc-based drills achieved the best seed to soil contact in the wet conditions and resulted in the highest crop establishment, with the Horsch Avatar coming out top at 81% establishment, closely followed by the Ryetec (79%), with the tine-based Amazone Cayena (70%).

Mr Jagger says: “We’d had a fair bit of rain prior to drilling in March, so generally all drills performed well in what were very testing conditions.

“There were some differences in plant establishment but, as a rule, establishment was all within the typical range we’d expect nationally. We didn’t find any clear differences in tillering.”

Interestingly, leading tine or leading disc versions of the Claydon Hybrid were compared, and both performed similarly in terms of establishment, however the tine-based machine seemed to produce a more even crop height than the disc drill, he says.

“In some conditions a disc drill might work better, in others it may be tined machines. The important thing is to understand the soils you’re working with and what you need the machine to achieve.

“We plan to continue the work next season and a more in-depth comparison of tine and disc-based drills is something we’re considering.”

Further analysis of the results from this year’s trial, looking at average spring wheat establishment across all drill types for each cover crop mix, revealed establishment was highest in the MaxiRooter area, at 68%. The range of rooting characteristics in the multi-species mix had a marked benefit on soil friability, aiding the effectiveness of the drills and benefiting plant growth, says Mr Jagger.

“MaxiRooter contains a high proportion of linseed, which is a fibrous root mass that really helps soil conditioning. It also contains daikon tillage radish, which can punch through tighter soil layers and open the structure. The mix will be sown across the whole 10ha area this autumn, with a view to putting the demonstration field into spring wheat again.”

Although the overwinter bare stubble returned the next highest average wheat establishment, Mr Jagger says this was only because crops were able to utilise more residual soil nitrogen, much of which had been taken up by cover crops in other plots.

“There may be a short-term gain from the available nitrogen, but don’t forget some will have been leached out of the bare stubble over winter. Growing a cover crop captures those nutrients before slowly releasing them as material breaks down over the following seasons, building organic matter at the same time.”

Adding oats to the mix further highlighted the importance of tailoring cover crop choice to soil type and cropping, he adds.

“We found the oats left the topsoil much wetter at drilling, which we expected. That may be beneficial if you’re sowing something like peas later in spring to retain moisture, but for an earlier-sown cereal in wetter conditions, it wasn’t favourable.

“You’ve got to understand your own soil conditions and the benefits individual cover crop species bring to different situations. There’s a narrow window to establish cover crops and a cost to growing them, so they’ve got to be treated properly for best results.”

The site was assessed for structural issues and suitability for direct drilling prior to the demonstration. Omnia field layers were prepared for seedbed condition, silt/clay content and a variable seed rate plan produced.

Low pH hotspots identified with a TerraMap scan, were treated. Mr Neale says: “The success of all the drills was largely down to building resilience in the soil during the previous season.

“Despite wet weather prior to drilling, the soil aggregates were stable, allowing good seedbed water movement and seed to soil contact. Success with cover crops and minimal soil movement drilling techniques is a case of assessment and planning.”

 

Key messages

  • Be clear what you want cover crops to achieve – such as soil conditioning, alleviating compaction, building organic matter, adding nutrients
  • Spring is the best time to assess soils for compaction, when there is sufficient soil moisture, not summer, when soils are hard and dry
  • If mechanical subsoiling is required, ensure it is done before sowing a cover crop
  • Tailor mixes to individual requirements and make sure they fit the rotation. Consider potential allelopathic effects, pest or disease carryover to following crops
  • Termination timing is key to drilling effectiveness. Be clear what the drill can handle in terms of soil conditions and crop residues, allowing sufficient time for material to die back
  • Understand the soil conditions that different cover crop mixes create. A high grass content, for example, can leave a tight topsoil due to dense root mass
  • Using multiple species brings diverse rooting characteristics, which improves soil friability and drilling operations

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