I have been rereading the comments that followed my post “No guarantees” – an amazing stream of good thoughts, theories, and hard-won advice. One of the topics that jumped out at me was the bitter claim that no matter what, if we harvest a garden or field, we are depleting fertility by definition.

Wildearthman wrote: “The only historical agriculture found that could be sustained more or less indefinitely occurred on river bottoms where fresh fertility was imported each year from distant mountains. Even with composting, cover crops, and green manures, fertility continues to decline. On my few acres in the Cascades, the topsoil was stripped in clear-cutting. The subsoil is a good quality loam, but I have to import a lot of fertility to make things grow here. How do you keep growing crops in the same old soil, drawing out nutrients with each crop, without at some point adding fertility from somewhere else?”

Jan countered: “The key to continued fertility is to close the nutrient cycle.”

I reasoned that if nature can go from lesser fertility to greater, so could we. Even in pristine forests or grasslands, animals harvest and take away. They leave their poop, true, but they carry away all the energy they need to grow and maintain themselves. That is not returned to the soil until the bird or elk or bison dies.

Osker suggested that a harvest should not be a subtraction from the ecosystem. Clearly, this is possible: a farmer thins the forest he planted 15 years ago, so that all the trees have greater access to the sun; win/win. Relying more on perennial crops – mainly nut trees — is part of Osker’s  strategy.

And so all this put a bee in my bonnet. Is it possible to garden in place without depleting fertility? Is it possible to work a field over generations without the soil sinking lower and lower, with the topsoil growing thinner and thinner?

Then I remembered John Jeavons. I took note of him way back when primarily for his effort to shrink the land needed to grow enough food for one person per year. Only now am I discovering his solution to the very question opened up by my friends on this blog.

To refresh folks’ memory, Jeavons runs a farm in coastal California where he decided to find out what is the minimum of land that will adequately feed a human with a vegetarian diet. He proposed 4,000 sq ft (8,000 with pathways etc.) and now has expanded those numbers to 10,000 in fertile situations and 16,000 in challenging situations. Over time, his experimentation developed into a whole system that has a number of components which are elucidated here.

I am not intending to evaluate his system. I will only alert you that his popular book How to Grow More Vegetables has a new edition coming out in July.

I do think that Jeavons has possibly resolved the puzzle of fertility maintenance or even – gasp – its increase. Jeavons – and this is stupendous – keeps only 40 % of his land for growing human food, and allots 60% of it to growing soil food. To feed the soil, he grows nitrogen fixers, carbon-rich crops, root-dense plants, and perennials with deep roots that bring up subsoil nutrients. (He is no slouch with humanure either). He carefully composts the lot, and adds buckets of it to the beds.

So here is my question. Is this the solution we have been looking for? I can see the face of an Amish farmer being told he has to plow up another 60% of his current fields, just to feed the soil. And why 60%? One of my annoyances with Jeavons is that he will make statements neither supported by an explanation nor by a reference to other sources. For example, he claims that vermicomposting is not suitable to his method because the worms make the nutrients too available. Who says?

Minor quibbling on my part. I walked a field this morning, 100 ft by 100 ft, and took in visually the area that would be dedicated to feeding soil. Huge! Feeding soil must precede feeding everybody else. What an idea! (I do believe that Jeavons does not strictly separate the soil feeding beds and the human feeding beds – for example, rye will give its grains to humans, but the bulk of the plant is pure carbon. And the decaying roots feed the soil directly.)

Feeding soil will not do you any good if you let it all run away in erosion. Crop rotation is a topic of its own, and so is minimal tillage. Rock dusts do not steal fertility elsewhere yet may help fertility in your garden (as they help the fertility of tropical islands lucky enough to lie within the plume of the volcanic dust). Wood ash enriches acidic soils, there are compost teas and plant brews, the word is still out on biochar (which can be easily obtained by burning some brush). Try throwing a little in your chicken coop along with some corn to encourage scratching, and soon the coop will have no dust, no smell, and no poop stalagmites. Later apply the bedding to your garden. No chickens? Here is a recipe: a bit of biochar, some worm castings, a bit of corn meal or flour, bit of pee and a bit of rock dust. Mix well, and let ripen a few days. Voilà!

This of course does not apply to those who sell their produce. They have to import fertility. But getting municipal compost or certain horse manures seems not so much like stealing, but recycling. Nah? Another thought… the ancient practice of letting land lie fallow (as long as it’s covered by vegetation, and grazed occasionally) can be thought of as a nascent glimmer of understanding that the soil needs to be fed.

But back to the main topic. Will the magic application of 60% soil food keep your-mine-our garden’s and field’s fertility increasing? Is this the solution we have been looking for 7,000 years?

Ecology Action garden

Advertisements