Are You Micromanaging Your Soil?

posted in: Science | 5

mi·cro·man·age: to manage or control with excessive attention to minor details.

As a means to improve soil management, I commend the high interest in soil biology among farmers and gardeners. However, I have noticed the tendency for this interest to be combined with the thought that we should be able to fine-tune our soil biology for the good of our crops, health, sustainability, democracy, justice, and peace. OK, mostly just crops and soil health, but exaggeration does seem to be rampant when it comes to expectations.

Soil samples from the Newberg-Dundee Bypass project. Image by the Oregon Department of Transportation via Flickr.
There’s a lot of soil diversity, and that doesn’t even include the diversity of soil microorganisms! Soil samples from the Newberg-Dundee Bypass project. Image by the Oregon Department of Transportation via Flickr.

The problem is that the idea that we can accurately fine-tune our soils is wrong. Unfortunately, this has not stopped a swarm of salesmen from swooping upon budding soil micromanagers hawking their bio-products. And this is not just at organic farming conferences where biological products are commonplace. I collected this list of products at last year’s Pacific Northwest Vegetable Association conference in Kennewick: Bio Secure, Bio Safe, Bio Innovator, Bio Flora, Bio Generator, Byo Soil, Byo Gon, Bio Forge, Bio Works, Bio Terra Plus, and BioBurst.

I did not evaluate these products and I am not saying that none of them work. My targets are those practices, potions, and promises that claim to “fine-tune your soil biology for better ____.” Fill in the blank with balance, crop yield, crop quality, nutrient concentrations, pest control, and my favorite, which comes from a recent phone call from a salesman, “stripe-rust control.” (Stripe rust is a foliar fungal disease of wheat with spores that blow from state to state. How a soil product would cure this, I haven’t a clue).

Artwork for USDA's Natural Resources Conservation Service (NRCS) campaign on the value and benefits of productive, healthy soil management. Image from NRCS via Flickr.
Artwork for USDA’s Natural Resources Conservation Service (NRCS) campaign on the value and benefits of productive, healthy soil management. Image from NRCS via Flickr.

.

The problem here is not the desire to manage soils; it is the degree of control that they are claiming. Peddlers of these products claim to be able to give you “a perfectly balanced soil,” “equilibrium”, “fine-tuning your soil’s biology” (all taken from actual product advertising). They make it sound like managing the soil is like blending a fine wine, a little of this, a little of that, and we can solve any problem. However, fine-tuning implies understanding, and we do not understand “soil biology” at anywhere near the detail to allow us to micromanage it by adding this enzyme or that bacterial species. To think otherwise is folly.

Soil scientists estimate, don’t ask me how, that we know only about 10% of the soils species. Most species do not grow in the lab and so we cannot study them in traditional ways. With new genetic methods, researchers can better determine what is in the soil, but even this data has to be compared with DNA libraries of known species. In addition to the unknown species, the sheer diversity is staggering. I have seen estimates of 10,000 bacterial species in a gram of soil. Who can say they understand this underground jungle enough to fiddle with the details?

What to do in the face of such complexity? First, don’t try to tweak the details of your “soil biology.” Rather, take the big view and focus on the principles, which are, as I see them:

.

  1. Feed the soil – If you want to change a bulk physical property of the soil, you have to use bulk materials. The hitch with many non-fertilizer “bio-products” is the small amounts actually added to the soil. If you do the calculations, many are adding about a drop of product per square foot, sometimes much less. Although some pesticides are effective at such levels, I don’t think it is reasonable to expect one drop to change your soil biology. Bulk organic materials, on the other hand, provide food for your soil biology. These can be grown on-farm, like cover crops and green manures, or imported materials like manure, compost or organic waste. Once fed, the soil biology does what it does, building structure, cycling nutrients, etc.
  2. Stay out of the way – Conserve what the soil does naturally. This includes minimizing disturbance (tillage) and keeping the soil covered as much as possible.

Sounds too simple? The principles ARE simple, but the details of doing this can be challenging. That’s why it is tempting to look for “organic-matter-in-a-jug” solutions. Resist the urge to micromanage and save your money for proven soil building practices.

If you do want to test some of these non-bulk products, I recommend looking for those that are focused on doing one specific thing at one specific location in the soil, such as inoculating of plant growth-promoting bacteria in the seed furrow. Then work with your local Extension educator to set up a reliable on-farm test. Be very skeptical of everything else.

Follow Andrew McGuire:

Andrew McGuire is an Irrigated Cropping Systems Agronomist for Washington State University Extension. He works with farmers in the Columbia Basin of Central Washington in improving soils through cover crops and high residue farming systems.