John Kempf interviews Erwin Westers, an innovative Dutch grower who harnesses a technique called Flächenrotte to drive soil biology, improve seed vigor, and boost whole-system resilience

Kempf. Tell us a little bit about your context and the scope of your operation.

Westers. We have a biodynamic seed farm in the north of the Netherlands, at the border of the sea. We own a part of the dyke that keeps the Netherlands dry from the sea, and we own a part of land that is outside the dyke, which is a salt marsh. 

Kempf. What are the various crops you’re producing seed for?

Westers. We are producing seed for potatoes, radish, kale, turnips, nasturtium, and a lot of wildflowers also, and lupins. It varies every year. We have a couple seed buyers in Germany, Austria, and Switzerland, two in the Netherlands, and even one in North America.

Kempf. What does higher-quality seed look like exactly? What are some of the parameters you’re trying to achieve, and how are you approaching that?

Westers. If you buy a seed, most people look at the germination rate. And that is one of the most easy-to-research parameters of a seed. But vigor is also important, and seed companies don’t always put that on the label. We have seen that by giving seeds a very good life on our farm, the farmer or gardener who buys the seeds gets a better plant. 

I had an “aha” moment about 10 years ago. We didn’t have enough untreated seed potatoes from one farmer, so we got more seed from another farmer. We grew them on the same amount of land right next to each other. The plants were optically the same, without optical disease, and they were checked in the laboratory, and the field was treated all the same. But when we harvested, I saw that on one part of the field there was much more rhizoctonia disease on the tubers — those ones have to be thrown out because they damage the sprout the next year. And the yield was 25 percent less. 

That farmer I bought these seed potatoes from did something that gave me a worse harvest. And if that holds true for a seed potato, which is a big storer of nutrients, I realized that must also translate to smaller seeds.

Kempf. How do you measure vigor?

Westers. If you have different seed lots, and you put them next to each other, you can clearly see the difference. The one that grows rapidly or develops best in the first two or three weeks, when most of the energy is coming from the seed, has the most vigor.

Kempf. A friend of mine purchased arugula seed from a mainstream seed supplier, planted most of what he had purchased, and had some leftover. And the arugula seed that he planted, he harvested most of it, but some of it he let go to seed. He had worked for years to build up his soil microbiome and soil mineral balance. He harvested seed from some of the arugula that he had planted, and he had much larger seed size — he had about a third of the seeds per pound as the original seed that he had purchased. And then he planted what he had leftover side by side with his own seed, and his seed that he had saved from the larger seed size reached harvest size 11 days earlier than the seed that he had purchased.