Fine Gardening's guide to vegetable growing Grow just arrived, and I was glad to see a piece by Roy McGinnis in defense of manure.
Manure is beautiful. The first time I ever saw explosive growth in my vegetable garden was the year my neighbor allowed me to take a pitchfork to her sheep stalls and wheel the combination of straw and manure across the road and dump it on my planting beds. I promise you, I never noticed any such happiness on the part of my vegetables back in the early days when I used to fling handfuls of bagged organic fertilizer at them.
The manure cycle is beautiful. Waste made productive. Mix a bit of livestock and some food crops, and you have complete self-sufficiency.
So I was profoundly shocked a few months ago when I finished the superb introduction to soil science in Jeff Lowenfels' and Wayne Lewis's Teaming With Microbes: A Gardener's Guide to the Soil Food Web and got to this thought:
Human feces and pet feces should not be composted because of the possibility that disease organisms might survive even the high heat of the composting process; for the same reason, we personally discourage the timeworn pratice of using other manures in compost. Why take the risk when you don't know what kind of antibiotics and other drugs were used to feed the animals. Who wants to be worried about E. coli?
Roy McGinnis ignores this issue, saying only, "While it's all right to add manure directly to garden soil in fall (farmers do it all the time), I've found that cow, horse, and bird manure are best if composted first."
The ever fair and sensible Jeff Gillman has this to say in The Truth About Organic Gardening: "The practice of adding compost, including composted manure, to soil is a good one as long as you compost appropriately." Gillman, however, does cite a study that found that E. coli O157:H7 can live in uncomposted manure for 21 months.
I wasn't happy to learn from the abstract that E. coli O157:H7 can survive in manure frozen at -4 degrees Fahrenheit for 100 days, because there we have my manure handling plan. I try to spread it on my vegetable beds at Thanksgiving, but this year I didn't get to it and just left the pile frozen and will spread it in April.
A quick look-through of the other papers that cite this one suggest that the science is a bit all over the place, from the truly horrible–slugs may be vectors for E. coli O157:H7, depositing it onto lettuces; lettuces take up E. coli into their internal tissues, where it cannot be washed off; E.coli can set up shop and live in the soil–to others that say what I want to hear: that even with sloppy, room-temperature composting, E. coli disappears after 28 days.
Am I giving up manure? No. I trust that the waste treatment process in my garden soil is far more complete than that in any highly controlled study, and my manure does sit for a long time before it goes near a vegetable.
And has anyone ever gotten sick from the food in a home garden?Posted by Michele Owens on March 13, 2009 at 1:29 am, in the category Ministry of Controversy.