There’s Just Not Enough Manure in the World

Andrew McGuire is an agronomist working in the Columbia Basin’s irrigated cropping systems. His current focus is on helping farmers bui

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6 thoughts on “There’s Just Not Enough Manure in the World

  1. I’d be interested to see how composting toilets and returning the spent animals to the soil affects the fertilizer deficit.

  2. True as Bill states, some New England Dairy Farms have nutrient management issues, especially those that have concentrated their manure on the closer fields. The vast majority of these farms don’t purchase any P as commercial fertilizer, it comes onto the farm in the form of grain. We are transporting the P from the grain belt to various regions. The same is more of a fact in the poultry and swine industries that feed a higher concentrate diet.

    I also agree with Gene that 300 million people create a lot of “manure” of which the vast majority of the nutrients are wasted.

  3. In my youth, gardeners would ask a farmer for a load of manure for their vegetable garden. They especially valued that “old manure” because it would burn plants and. . . well, they never told us the rest. My guess is that this way of importing manure had less to do with fertilizing value than it did of soil health: it’s just that no one really had the vocabulary (root exudates, micchorizal fungi, etc.) to describe what they knew was necessary.

  4. These numbers look reasonable as far as manure goes. Manure is only a portion of biological nutrient availability. Most crop nitrogen needs can be supplied directly through biological N fixation. On the carbon side, root exudates are likely a bigger source than plant residue.

  5. Besides “peak oil” and “peak water” there’s also “peak Phosphorous and Potassium”, mined resources that will become increasing scarce ($$$).

    While we may not have enough animal manure, we ship tons of food to cities, somehow that waste stream needs to return back to the landscape that produced the initial food.

    If we account for 300 million people consuming and producing “manure” would there be enough to fertilize more of the landscape assuming we could remove human pathogens and heavy metals from the waste stream?

  6. Many New England dairies have nutrient management issues — usually an oversupply of phosphorus — because so much grain is imported from extremely distant fields. It’s currently considered acceptable practice to over apply P on fields where the risk of runoff is low enough, but you have to wonder what’s going to happen eventually.

    I also heard an interesting piece about the fact that Vermont imports quite a bit more P than it needs to sustain its ecosystem — and they weren’t talking about just agriculture. Just about any economic activity you can think of that brings in materials of just about any kind from outside a bioregion — food service/hospitality, manufacturing, transportation, etc. — all bring in phosphorus with them, and generally speaking there’s enough wasted that a lot of it stays behind when the finished products are used or shipped out of state.

    Meanwhile, I wouldn’t be at all surprised if grain-shipping areas like the corn belt of the midwest have long term P deficits.

    Interesting problem to think on, and yet another externalized cost of the beltification of agriculture and industry.

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