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Choose cover crops with care – Farm Contractor and Large Scale Farmer

Farmers considering using cover crops must select the right crop for the job ...

Any cover crop should include a combination of species that are different from those in their main rotation, Dick Neale, Technical Manager from Hutchinsons, told visitors to an open day on the subject at Driffield, Yorkshire.

A quick show of hands of his audience of invited farmers revealed that only a few had tried growing them, but many more were thinking about using them.

He urged the latter group to seek advice before they made decisions and ensure they chose an appropriate seed mix. A typical cover should contain a combination of ‘forb’ (herbaceous flowering plants) species, brassicas and legumes.

Hutchinsons had formulated the seed mixes it offers on this basis so – even if some species failed to grow – the species that did thrive would ensure effective ground cover.

Those species that failed to grow played an important role, he said, as their failure could reveal information about the soil. Farmers should assess the weeds that grew on a similar basis.

“They are all telling you something about your soils,” Mr Neale said. “It is important to grow covers that are different to the crops in your main rotation. If you have a cereals-based rotation there is no point using oats as a cover because you are not introducing any diversity in terms of root type or biology.”

Oats also had the drawback that they tend to leave the soil damp, which can cause problems if they’re grown as cover ahead of a planned spring crop: “By contrast, a crop like buckwheat – which is hardly ever grown commercially – is very effective as a cover. Above the ground, it grows quickly and produces flowers that are exploited by pollinators and bees.

“And below ground, it generates a healthy root system than conditions the soil and helps release phosphate for the following crop,” Mr Neale said.

It has another benefit for those growing them ahead of autumn-sown crops, in that it is usually killed by the first autumn frost. Most of the seed mixes that Hutchinsons now offer include up to eight species, with a balance chosen from each of the three main plant types.

It has launched some more specialist mixes, such as a vegetable mix that doesn’t include brassicas, a specialist fruit grower’s mix and a wide spectrum mix with 15 species.

One practical aspect of the main mixes is that the seeds are all much the same size. This avoids settlement and separation during transport and spreading, so all parts of the field receive the desired mixture. The final choice of which mix is most appropriate should also be guided by soil type.

On a heavy clay soil, the mix could include larger proportions of radishes and turnips that penetrate and ‘punch holes’ in the soil to aid drainage and also release nitrogen to the soil as they die.

On lighter types, where stabilisation over winter is important, they would include species like legumes with finer, more fibrous rooting systems that help bind the soil together.

Mr Neale urges farmers to assess their soils before making decisions. “We can’t really make any decisions about managing the soil until we’ve had a good look and identified any problems,” he added.

In this respect, he recommended Omnia’s TerraMap system, which measures a range of soil parameters and turns that data into a high- definition map and he urged farmers to think more about the biology of their soil: “That is important to how you change how your soil behaves, and you can influence those changes by your choice of cover crops,” he added.

Using low disturbance techniques also played a part – and there was a line-up of nine drills in the field for visitors to assess drilling straight into an overwintered cover crop. “Ideally you need two drills – a tined model and one with discs. The tined drill will normally move a little bit of soil, so it effectively does a cultivation as well, after which either drill can work into that little bit of tilth in the autumn or spring,” Mr Neale added.

And they should do everything they can to increase worm populations, which started with not ploughing down crops residues. Deep-working species can take material well down into their burrows, while shallower working species feed off it and keep it in the biologically active shallower soils.

DRILLS PUT TO TEST

At the same event, a line-up of nine drills took to the field on a damp heavy clay loam soil. They drilled at right angles across four different seed-beds, three with cover crops and one with just stubble. One plot was sown with Hutchinsons MaxiCover – a multi-purpose blend of three forbs, three brassicas and two legumes – and the second with the same product with added oats.

The third cover crop was the company’s MaxiRooter mix, which combines species like linseed and Daikon radish (known as ’tillage radish’) to alleviate minor shallow compaction or slumping issues.

The nine drills tested were:

  • Mzuri’s Pro-Til3T tills a thin strip into which its coulters place the seed, while leaving surface residue undisturbed. An optional front cutting disc is available to cut through trash if required. Fertiliser can be placed in a band below the seed to ensure swift availability.
  • Sumo showed the 2020 version of its DTS (deep tillage system) drill which uses a front cutting disc and tine to prepare a channel for the drilling coulter, which can place both seed and fertiliser before a covering disc and press wheel complete the operation. Recent updates include an upgraded fan system and hydraulics.
  • Ryetec showed the MAAG SSP drill, which uses floating disc coulters with individual pressure adjustment and depth control to place seed accurately, even on undulating land. Drill coulters are set in two rows at the front and back of the drill frame to optimise trash clearance.
  • Weaving uses a 25-degree angle on its drilling coulters, which open an angled slot into which it places the seed, before closing it effectively with a press wheel. At the moment Weaving’s widest model is eight metres, but the company is planning to launch new, wider models later this year. Claydon showed its Hybrid drill, which uses the company’s in-line tine design to alleviate compaction and create both drainage and tilth in the seeding zone. Stand staff stressed the ease and speed with which the drill’s configuration can be changed to handle different drilling conditions.
  • Sky stressed the versatility of its Easy Drill HD and its low power requirement, with a 6m model requiring 180hp and models available from three to eight metres. They can work in anything from well consolidated ploughing, through non-inversion tillage, grassland, and direct drill through stubble or cover crops.
  • Amazone’s Cayena-6001C tined drill is designed to work in hard soils, but can also work in either cultivated soil or drill direct. The company now offers a new hard weld finish on drilling coulters to extend working life, and says a 6m model can be pulled by a 150hp tractor.
  • Horsch showed its Avatar drill, which features a duel seed/fertiliser hopper with coulters separated into two rows, giving a 33cm spacing on the same row that aids trash flow and enables it to drill through cover crops. The machine’s comparatively light weight is spread on large tyres to minimize compaction risks.
  • John Deere showed the 750A drill, which uses a tried and tested Pro Series double disc opener set at a seven degree angle to open the seed slot and achieve precise seed placement. The company stresses the machine’s low power requirement (130hp for a four metre drill) and economy of use.

Catch & Cover Crop Mixes 2022

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