Thursday, February 12, 2009

feeding the soil

This post is the second part of an excerpt from _A Nation of Farmers_ regarding soil.

If a healthy soil is full of death, it is also full of life: worms, fungi, microorganisms of all kinds.... Given only the health of the soil, nothing that dies is dead for very long.

—Wendell Berry

One of our hobbies here in the United States the hyper-distillation of ideas. We’re trying to perfect the sound bite, a pursuit made necessary by a mainstream media that consists of a handful of news tycoons trying, in a fair and balanced fashion, to offer us only two perspectives of exactly 150 seconds per idea. Never mind that some of these complex ideas have to be dumbed down immensely to fit into this short window; the complex versions are really important to the lives of the citizens of our nation. It’s as if what really matters is whether the nightly news can afford to fit in a quick story about the state of American health care between commercials for burger joints and drug companies.

A good example of our oversimplification can be seen in our whole approach to the question of plant nutrition (well, human too, but that’s another discussion). NPK stands for nitrogen, phosphorus (phosphorus pentoxide) and potassium (potash or potassium oxide). K is the atomic symbol for potassium. P was already taken and the Latin for potassium is kalium, so that’s how we get K. See how complicated this is getting already? But stay with me here, this is important. This acronym NPK describes three major plant nutrients and helps to describe the ratio of the each as a percentage of weight in any particular synthetic fertilizer. For instance, a bag of fertilizer labeled 20-7-10 has 20 percent nitrogen, 7 percent phosphorus and 10 percent potassium. The remaining 63 percent is ballast, or stuff not necessarily useful to the plant.

NPK represents only three of the six plant macronutrients. That is, these are things that the plants need to survive. The other three are calcium, magnesium and sulfur. In addition plants need varying amounts of micronutrients including iron, manganese, boron, copper, molybdenum, nickel, lithium, chlorine, zinc, selenium and others. But ask someone who sells fertilizer about how to choose which fertilizer to use in your garden and they will rarely get past NPK, any more than politicians get past the soundbyte. And not only do we have a hard time getting past those three nutrients, we almost never get to the delivery system of these nutrients, which is just as essential.

Most people think in terms of plants absorbing needed nutrients through their roots. The truth is much more complicated. In fact plants feed themselves through a host of symbiotic relationships between the plants and other microorganisms in the soil. The plants in turn feed the microorganisms sugars. In some cases the connection is a physical one. Sometimes the roots of plants are penetrated by microrhiza; other times the plants are fed by nearby neighbors. The soil is a community of living organisms that makes up one of the most densely populated ecosystems on the planet.

Try to imagine millions of living organisms in one cubic centimeter. It is this community on which all of us who eat plants—or eat animals that eat plants—are dependant, which is to say it’s much more complicated than a three-letter abbreviation. Forget the idea that plants eat first. Microorganisms are at the head of the table.

It is true that nitrogen, phosphorus and potassium are very important for the successful growth of plants. It’s just silly to say that the right combination of these three alone can continue to provide enough food to feed us. The very reason we need to add N, P and K to our farm fields is that we’ve stripped off much of the topsoil in which the healthy ecosystem of soil microbes lived. In many cases the remaining microbial communities were then killed by applications of synthetic fertilizers and pesticides. The topsoil of many industrial farming operations is rightly described as simply lifeless sponge onto which chemicals are poured in order to make up for this community that once nourished the plants without such inputs.

And perhaps if this was a simple trade, the life of the soil traded for better living through chemistry, it might be a trade we would be willing to make. But as we have discussed elsewhere in this book, these chemicals have negative effects on human beings as well as destroying entire ecosystems such as our waterways. The cost in terms of human health and in terms of ecological health are two strong reasons for imagining a different way of growing food. Another is the economic cost.

Frank Dean of ICL Performance Products says the price of Merchant Grade Acid (MGA) used to process phosphate rock into phosphorus fertilizers rose between 25 and 30 percent in 2007, while “fertilizer phosphates, which use MGA as a feedstock, have increased by as much as 70% to 100%.”[i] That means some fertilizer phosphates have nearly doubled in price only a year. Meanwhile, the price for potash rose by 230 percent in April 2008, and potash production is increasingly concentrated among only a few companies.[ii]

No projections include a drop in demand for food or for the fertilizers currently used in their industrial production. In fact it is precisely the opposite. “World fertilizer demand has grown by 14% in the last five years—Equivalent to a new U.S. market,” said Deen. Phosphorus and its uptake by plants is a somewhat complicated matter, but the practice of mining rock phosphates from the other side of world and shipping them to the US for use as fertilizers is likely not a practice that will increase in the future. While a worldwide economic crisis may reduce consumption of energy, it is unlikely to dramatically reduce desire for food.

Meanwhile, synthetic nitrogen fertilizers are extracted using natural gas (NG), which is itself a finite resource, one likely to decline in production during the next decade or two. Already we’ve witnessed fertilizer companies moving oversees to parts of the world where NG is more abundant. This is another way that we face increasing reliance on faraway places that don’t have our interests at heart. It is not just that dumping massive amounts of synthetic nitrogen fertilizers is bad for our health and bad for the environment; doing so is fast becoming prohibitively expensive and further increasing our reliance on parts of the world where we aren’t popular.

And natural gas isn’t the only fertilizer macronutrient potentially in short supply. Research Patrick Dery has concluded that the world is facing a peak in phosphorus production.[iii] Industrial agriculture strips phosphorus rapidly from the soil, and we are mining rock phosphates rapidly. This means that the price will rise and the ability of the world’s lower-income people to buy fertilizers to grow food is in real danger. In the longer term, we must address the problem of phosphorus availability in order to ensure a reliable food supply for our grandchildren.

But is there an alternative? The short answer is yes. The long answer is more complicated than a three-letter initialism but is not beyond the understanding of those who study soil and understand how the microbial community therein can help in a world in which we can’t afford the costs of synthetic fertilizers. There more than 100 microorganisms, including rhizobia and several yeasts, that fix nitrogen from the atmosphere and make it available to plants.[iv] These microorganisms provide plants with nitrogen on demand—far more useful and complex than simply pouring on the fertilizer. That is, if the plant is in need of nitrogen, the microorganisms make it available. If the plant no longer needs more nitrogen, the microbes stopping making it available. Nitrogen doesn’t have the opportunity to build up to toxic levels in the soil or run off into nearby waterways. Microorganisms also make available other nutrients, macro and micro alike, and are the key to developing a sustainable soil structure for supporting permanent agriculture.

Ever wonder why forests don’t need to be fertilized, how towering oak trees came to be without someone applying the right combination of NPK? Microorganisms break down carbon and leach weak acids that break down minerals, making them available to plants. Those oak trees and the other plants in the forest rely on the nutrient recycling undertaken by the microbial community naturally occurring in the soil. We can mimic this process. We can establish healthy soil communities and provide nutrients for recycling. We can sequester carbon, a necessary part of this soil recycling program, helping to offset carbon emissions while we build soil. (More on this later.) The typical NPK approach to providing the nutrients necessary for useful industrial agriculture needs to be turned on its head. The answer isn’t an initialism. It’s fostering natural soil systems and the communities of beneficial microorganisms that make up those systems and protecting them at all costs.

That doesn’t mean we won’t have to fertilize soils if we continue removing agricultural products from them—we will. But we can do so with organic materials. Indeed, it is a basic premise of this book that we will probably have no choice but to shift toward organic agriculture—not out of some elitist preference but because we simply can’t feed the world any other way. Reliance on distant macronutrients and fossil fuels is a recipe for disaster as those things rise in price and availability. Many people have assumed that if we cannot get these things we are doomed to starvation. But this is not true.

Not only can we make nature work for us but we also have an enormously valuable resource that we largely waste—human manures and human urine. On a planet with 6.7 billion people, the one thing we have in abundance is human outputs. These outputs can indefinitely recycle the phosphorous and nitrogen we’ve been using all along, keeping world food yields high.

To do so, we will have to shift our relationship to our own manures. Historically in many places there was a tie between city and country. We will talk more about recreating the ties between urban and rural cultures, but one way we will probably have to do this is by the return of human biosolids to agricultural fields. In rural areas, we will have to take up the composting of human manures and the collection of human urine.

We tend to be very squeamish about these issues, but we will have to face these subjects head on in order to keep up our food supply. Our food supply depends on our ability not to treat these complexities as soundbyte issues, but to truly understand the ways in which we can transform our liabilities into assets.


[i] ICL Performance Products presentation, Concord, N.C., 1.10.08.

[ii] (accessed Nov. 25, 2008).

[iii] (accessed Nov. 25, 2008).

[iv] Personal communication with Ron Danise, a certified arborist who has worked in the field of arboriculture since 1964, during which time he has researched and developed organic soil amendments that develop living soil systems.


bryant said...

Nice summation of the soil food web and the perils of "chemical" ag. I was hoping to see a plug for Joe Jenkins' Humanure Handbook, but I understand that this is an excerpted section of your book.

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