Sunday, February 28, 2010

Fertilizer News

Last week a link to Tom Philpott’s article “New research: synthetic nitrogen destroys soil carbon, undermines soil health” showed up on Energy Bulletin, one of my favorite news sites. The article was originally published in Grist.

The article’s title pretty much says it all: a couple of recent (2007, 2009) studies by soil scientists working in Illinois (and a 2009 study by soil scientists in Iowa) support what some very old sources — published before WWII— had claimed, that use of synthetic fertilizers is bad for soil. What’s bad is that the readily available nitrogen speeds up growth of soil bacteria and fungi; as they grow, they do their usual job of decomposing organic matter more quickly, which results in soil with lower organic matter content.

It has been thought that agricultural soils on which plant debris had been left and then turned under would serve as storage for carbon, which could help mitigate climate change, but the new studies suggest that the industrial farms that rely on synthetic fertilizers are not going to be useful as carbon sinks.

In addition, soils that are lower in organic matter drain less well, hold less moisture, hold nutrients less well, and have lowered numbers of nitrogen-fixing bacteria. As the spaces normally held open by organic matter in the soil close because of the loss of that organic matter, the soil compacts and air is squeezed out. Roots need those air pockets, and so do many members of the community of micro- (and not so micro-) organisms that live in the soil.

I’m writing about this for a couple of reasons. The first is that not everyone who reads my blog reads the same websites that I do, so they might have missed this news. The other is that I had just about decided to save some money this year by using some synthetic fertilizer on my veggies. Obviously, I am going to have to change that plan (back to the cotton-seed meal, kelp meal, etc).

I would say that “Ignorance [was] bliss,” but I am glad to be able to avoid harming my garden’s soil. I may have to drive back out to that horse farm for another load of manure, though.

NOTE: The article discussed here is one in a series posted on Grist about soil nitrogen. Tom Philpott has written them all.


  1. Excellent post, thank you for taking the time to share this information. I started my seeds yesterday, looks like spring has sprung. Peace

  2. This is a good post.It seems the more we learn,the more the path leads us to the old,slower ways of the past!

  3. Well, it seemed like useful information to me, so I am glad that you both agree!

    Melodie, it does seem as though "progress" hasn't always had great results, but I will admit that using (and storing!) a bag of, for example, 10-10-10 is a heck of a lot easier than dealing with the truckload of manure. However, I plan to avoid the 10-10-10 from now on.

    Ruralrose, it is so great that you have started seeds! I love watching the tiny plants push up through the soil, often carrying their little seed coats on the end of one cotyledon. I am guessing that other gardeners get the same thrill from that as I do!

  4. I really enjoyed your talk yesterday at Smith Gilbert. I am learning alot from reading your blog. 2 questions. 1. Does 10-10-10 contain "synthetic" nitrogen? 2. What is the best way to begin a compost pile? (I have one of those plastic, square compost containers and have not had success). I hate that synthetic nitrogen will "eat up" organic matter that I add after the growing season....leaving my soil depleted of nutrients. Great article from Energy Bulletin. Thanks again!!!

  5. Hi Kathy! It was great to meet you, and I'm glad you enjoyed the talk. About your questions---yes, 10-10-10 does contain synthetic nitrogen. The Organic Vegetable Gardening booklet that was in the pile of handouts has a list of organic fertilizer sources of nitrogen that you can use instead of the synthetic fertilizers.

    For compost, it is important to combine both high and low nitrogen containing materials. The higher nitrogen materials include kitchen scraps, coffee grounds, fresh green weeds (without seeds), and fresh cut grass. These are often referred to as "greens." Materials with lower nitrogen content include dry leaves, dry grass clippings, straw, and hay. These are often referred to as "browns." It is also important to included a source of microorganisms--a shovelful of garden dirt--every now and then. For a pile that is built in layers, that shovelful of dirt should be a regular layer, as though you were building a lasagna with the greens, browns, and dirt.

    If you use the link near the top of my sidebar for UGA Ag Publications Search and type "compost" or "home compost" into the search box on that website, a whole list of publications about making compost will appear. Some of the publications are for commercial production, but some are for building home compost piles. If none of this helps, let me know.

    I will say that, in winter, composting happens more slowly. In my pile, the kitchen scraps are recognizable much longer in winter than in summer. Also, mixing the pile usually helps speed the compost. There are other factors that can affect the rate of composting (moisture level, ratio of green to brown materials in the pile), but regular mixing and inclusion of some healthy garden dirt is often enough to get things going.

    Hope that helps! Let me know if the pile still isn't working in a couple of weeks. If it isn't, I will need more details about what's going into the pile to sort out the problem, but compost isn't so complicated that figuring it out would be impossible (thank goodness!).

    Keep me posted on how your garden and compost progress through the season. I love to hear about other people's gardens!



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