The knowledge of Manfred Wenz

Organic no-till and direct sowing

Manfred Wenz has successfully developed no-till techniques for direct seeding of commercial grain crops, all while building up the vitality and organic matter of his soil.

This article, written by Stéphane Groleau, is based on a multi-day talk offered by German farmer Manfred Wenz in Quebec in 2006. The article was written for an organic agriculture magazine in Quebec and then translated into English.

We are in Victoriaville, a small town in Quebec, Canada. It’s February 28th 2006, and Manfred Wenz has just arrived from Germany to share his experiences with various sustainable and regenerative farming practices. Four days of talk and slides with an engaged audience of 180 people. The attraction: Manfred Wenz transitioned from conventional farming to direct sowing, and hasn’t used fertilizer for 30 years.

Wenz started by growing corn conventionally in 1954 on his 30 ha farm, though he destroyed his soil using pesticides, chemical fertilisers, and deep-ploughing (up to 45 cm deep) while rotating wheat and corn. He started with 60cm of rich, dark humus: by 1970, nothing remained but an eroded, compacted, subsoil-colored soil. No more life. Dead soil. Facing the facts, he converted to organic. But continued tillage didn’t help at all. It was only in 1980 that the answer came when he met Hans Kemink.

Kemink developed an approach and machinery in order to make permanent beds and avoid ploughing. This way, the tractor never compacts the growing area and there is an undisturbed space for the soil fauna. The machinery consists of two ridge wings to bring soil onto the beds from the path, and one sub-soiling tooth to lighten the bed. All crop residues are left on the middle of the bed to compost.

Even though Kemink’s technique helped increase the life and humus in Wenz’s soil, it wasn’t enough for Wenz, who was inspired by his travels in Brazil. There, he saw many different organic direct-sowing techniques and even bought a direct-sowing machine to experiment with in Germany. But it took 10 years before he managed to adapt the techniques to his farm.

Learning from nature

To succeed, he had to develop a greater understanding of the way Nature works. For Wenz, Nature has all the necessary tools to heal herself. “Nature has existed for 3 billion years; human farms for 10,000 years. From rock, Nature has developed all of the quality soil and the plants around us."

Wenz identifies four main natural mechanisms:

1. Soil fauna

In the soil, there is a system, a whole chain of life with about 1 kg of living organisms per square meter. “Nature has developed a series of specialists, billions of them interacting. There is no such thing as a parasite that needs to be eliminated. Just like a tractor needs all its parts to work, so does Nature." Wenz is especially fond of earthworms because they produce the best humus ever: worm castings keep nutrients in the soil where the plants feed themselves. Worms go up to 15 cm from their holes to get plant residues, making a tiny compost heap over the hole. Once softened and pre-composted by other organisms, worms digest it. Depending on the soil vitality, the number of worm holes goes from 200 to 350 per square meter. This would bring about 1 cm of good soil to the surface, which could bring around 100 m3 of worm castings per hectare. That‘s the equivalent of 5 to 6 cows per hectare! The rest of the soil organisms equal another 20 cows/ha more! So who said we need farm animals for manure?

2. The presence of plants

For Nature, a bare soil is a desert, an exposed soil becomes pale and dead like the subsoil.

Naturally, the soil will quickly get covered by weeds, what Wenz called “healing plants”: the soil knows its needs, so heads toward balance and recovery, just like a wound closing, Nature will grow the necessary plants. So in his five-year rotation, Wenz starts by letting these healing plants grow. A free green manure! Moreover, plants are able to extract insoluble nutrients by their association with micro-organisms in their rhizosphere.

3. Shade

By covering the ground, the plants protect against erosion, and create shade. Thus conditions become favourable for the soil fauna. The absence of light, produced by plants and mulches, also prevents other plants from growing or germinating. In the shade of the cover the ground develops a very fine layer of soil which hardens after harvest. To benefit from this particular condition, Wenz makes sure that a field is resown the very same day.

4. Successive layers

In Nature, nothing is buried. Everything accumulates in successive layers on the surface of the ground. A 3 cm layer, "the litter", breaks up these vegetable residues. The seeds do not germinate in this zone. Quality hay at the stage when one gives it to the cows is best to serve as mulch.

Now comes the direct sowing

For direct seeding in spring, one should first have in his field a plant that has survived through winter. This plant being alive in the spring, it will drain the soil of water. At the same time, such a plant should be able to stand up, allowing the sun to warm up the soil and activate life. The seeds of the desired crop must be sown 4 cm deep in order to be under the decomposition layer.

One such technique consists in establishing a rye green manure in the autumn. In spring, this is layed down at the flowering stage with a roller which breaks the stems. The root continues to push the sap until exhaustion. If it were cut, the rye would start a new stem. The roller is in front of the tractor and the seeder is behind. This way only one pass is necessary in spring, followed by another one at harvest time. That is fuel saving! One similar technique has been practiced since 2002 in the United States. Moreover, the Rodale Institute has a research program on the subject ( With this method, soybean makes its pods over mulch and remains clean from weeds.

For cereals, Wenz developed a tool able to work the ground precisely. Composed of blades shaped like a goose foot, it cuts the cover of white clover 4 cm high and deposits cereal right under this carpet. Wenz appreciated white clover for its small surface root system with a deep spiralling root going to the water table, while producing stolons (running roots) up to 50 cm long. Thus, this clover covers ground quickly if it is mowed or grazed, preventing even couch grass from settling. This clover carpet protects wheat, acting as an insulator. The sowing rate is 6-7 kg/ha using the varieties Huia, Nanouk or Kaia.

His main rotation looks like:

  1. Spring: light harrowing followed by white clover sowing and growth of the healing plants. During the season, first he’ll cut these plants; later on he’ll cut both clover and healing plants. In autumn, the clover covers the field and the winter wheat is directly seeded. This first year serves to feed earthworms.
  2. Spring: wheat grows on a bed/background of clover. After the harvest, by the end of July, the clover regrows. In autumn, the clover is lifted to weaken it before sowing wheat again.
  3. Spring: same as last year. When harvesting, the straw is left on the ground to feed the ground fauna. In autumn, light soil work, and rye sowing.
  4. Spring: rye harvest, followed by light soil work to let lost rye seeds and healing plants grow.
  5. Spring: rolling the rye and direct sowing of spelt, lupins, or soybeans.

A special crop is false flax (camelina sativa) from the cabbage family. Producing seeds for oil, it is inexpensive and a good companion for soybeans, field beans, and safflower. In mixed cropping, false flax ripens ten days before soybeans and stays until both are harvested. Being good heating oil, Wenz uses 30% of his production to fuel his tractors. As green manure, it makes a straight vertical stem that covers the soil rapidly.

Now, Wenz’s farm is owned by his son Friedrich who brought in biodynamics, even though they have been using no animal manure, no compost and no ploughing since 1969. But they now use bio-dynamic ‘preparations’ for soil amendments, some of which can be based on animal by-products so of course are not vegan-organic. Their wheat is sold to a local biodynamic bakery which neither buys nor sells any products grown farther than 14 kms. It seems that Friedrich went bio-dynamic in order to supply this bakery; the ‘preparations’ are not necessary for the growing system. For Wenz, the idea isn’t to reproduce exactly his method, but to dare to try and think about alternative ways. "The humus is the capital. One must live on interest and work to increase this capital. If not, the survival of our children is mortgaged." Today, Wenz has brought back 50% of the humus destroyed and wishes he had understood Nature earlier.

More about Manfred Wenz method: (in French or German)

18 June 2013
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