Which machine do you choose for sowing cover crops?

Increasing attention to soil quality have resulted in a significant increase in cover crop cultivation in recent years. For many arable farmers, cover crops are a serious cultivation that receives serious attention.

A cover crop is simply a crop, and that’s how you should treat it, seed suppliers rightly argue. “A well-crumbed seedbed ensures that even the fine-seeded components germinate quickly. Do not sow deeper than 2 to 3 centimeters,” the cultivation manual from DSV seeds states regarding their TerraLife cover crop mixtures.

It’s not just the advice of seed suppliers but also the principle that implement suppliers choose: sow a cover crop just like you sow grain or grass seed. Ensure sufficiently crumbled soil and sow accurately at the right depth. Covering, firming, and nature will do the rest.

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Working on flat and shallow stubble

Creating a neatly sown cover crop field in one pass on stubble land is often done with a combination of a tool in the front hitch and a rotary harrow with a seeder at the back. Disc coulters to sow evenly at depth through crop residues and then a bit of firming. This is how Dutch farmers have increasingly been sowing their cover crops in recent years.

Hans Hoogland, sales manager for Lemken in Northern Netherlands, noticed this as a trend a few years ago. This method is certainly not outdated, but there is now also a trend to work stubble fields as shallow as possible. Implement manufacturers like Lemken are responding to the trend of working stubble fields as shallow as possible. They offer cultivators with chisels designed to work shallowly. Hoeing instead of plowing. Also known as mulching.

Arguments to minimize soil cultivation are saving time and cultivation costs, keeping organic matter on top, and promoting soil life. Kuhn importer Reesink recognizes the same trends and notes that especially in plowless agriculture, flat sowing is even more important. This is due to the superficial incorporation of cover crops in spring.

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Sowing in firm ground

A next step that some arable farmers are taking is direct seeding in firm ground. No till and minimum till are terms originating from abroad that have been used for a long time for this purpose. Thierry Stokkermans, soil and agricultural systems researcher at Dutch Wageningen UR, follows this application within the NPPL project. According to him, farmers in France sow between 600,000 and 1,000,000 hectares per year in untilled soil. Globally, it is estimated at 125 million hectares. This cannot be directly translated to the Netherlands, but the conditions in Northern France are reasonably comparable.

What applies to main crops also applies to cover crops, according to Stokkermans. The right technique and timing are crucial for success. Time and fuel savings are a major motivation to sow a cover crop directly into stubble in one operation. In Dutch practice, this can result in a fuel saving of 30 liters per hectare for traditional cultivation and sowing, down to just 5 liters per hectare for direct seeding.

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Volunteer plants

“Wheat volunteers are not usually a problem,” says researcher Stokkermans, “as long as you don’t return with a cereal crop within two years. Otherwise, excessive volunteer plants can create disease pressure.” Stokkermans emphasizes the importance of a clean contact between seed and soil. The seedbed must be free of crop residues. With a lot of crop residues, this can be quite a challenge.

“We are still researching how and when to sow a cover crop,” says Michel Zeelen, key account manager at Dutch Joordens Seeds in Kessel (L.). Preceding crop, succeeding crop, and soil type are factors that play a role; therefore, sowing a cover crop involves a complex calculation with many considerations.

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Adapted machines

British grain growers have a lot of experience with seeding in untilled stubble. In the Netherlands, there are now several seeders from Claydon in use, and the also English Moore Unidrill is making its appearance. Both machine builders are based in the arable farming area on the east coast of England: Lincolnshire, Cambridgeshire, and Suffolk. There is large-scale arable farming in a climate and soil type comparable to the Netherlands (partly very heavy sea clay) and crop rotation. Their machines are designed to sow grain directly into stubble but are also suitable for cover crops.

In France, a system developed by a farmer is gaining popularity; he converted an existing vibrating tine cultivator into a seeder. It was named Bartsem, after the inventor. Instead of the original cultivator chisel, there is a steep, narrow chisel followed by an outlet from a pneumatic seeder. Frenchman Gilles Gauvin has been working with a Bartsem system for eight years and has further developed it over the years. Among other things, by equipping the cultivator with a roller with narrow cast iron rolls that press the seed furrows. French growers advise sowing as soon as possible, preferably within 24 hours after the combine harvester, as the ground is not yet dried out, and the chances of successful cover crop germination are highest.

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Overseeder

From Dutch soil, there is the overseeder from Landkracht Agri and Evers Agro, quite recently. Landkracht calls the machine the Single Disc Seeder, Evers named his machine the Dartmoor. It is designed as a overseeder for grass. The 3-meter version has discs spaced at 9.4 centimeters, followed by a star roller that presses the seed furrows. The depth can be accurately adjusted. The machine works with discs that cut through a grass sod, but also through crop residues, and is thus also suitable for sowing cover crops in a stubble. An arable farmer will not purchase it as an alternative to the existing seeder, but if the machine is available, it can be used universally. For example, to sow field margins, but also a cover crop.

Sowing directly into an untilled stubble means that you make the wheel tracks little or not flat. Some machines also have limited soil adjustment. This can be a limitation that can be partially overcome by diagonal driving.