Thursday, March 21, 2013
Soil re-mineralization for the rest of us
Now that spring is supposed to be here, I should be outside working on garden beds for the earliest spring crops. But we are having a late spring this year, at least compared to recent years. The temperature at the official St. Louis NWS site is 33F as I write. One year ago, it was 81F. The average high for today is 58F.
To really appreciate the difference between last year and this year, compare the picture of two redbuds in my backyard above (the small trees in the foreground), taken yesterday, with the picture below of the same two redbuds taken one year ago.
Last year the redbuds were in full bloom. This year, they haven’t changed much from midwinter. Granted, this year is closer to climatic normal than last ... but even the magnolias and most of the daffodils aren’t blooming yet.
With winter hanging on for at least a few more days, I have had time to read most of the way through Steve Solomon’s new book, The Intelligent Gardener: Growing Nutrient-Dense Food. Unlike his previous book, which I discussed here, this book looks in depth at one topic: why and how to re-mineralize garden soils. I’m really glad Solomon wrote the book because a couple of years ago, I had a subscription to Acres U.S.A. and read about soil re-mineralization and how important it is in that publication. However, Acres U.S.A. is written for farmers rather than gardeners. The articles discussing re-mineralization referred to many books written by and for farmers and their advisers. I could tell that different people used different systems, but I wasn’t up to reading the various books in order to piece together what might make sense for me to use on a garden scale. Fortunately for all of us, Solomon became interested enough in the topic and, as he puts it, honestly passed high school chemistry, so he could read much of the re-mineralization literature and interpret it for gardeners.
The first few chapters of the book explain why soils need re-mineralization and why composting and manuring are not sufficient to restore a full mineral balance to most soils, although they do benefit soils by feeding the soil microfauna. For those of us, myself included, who grow by the organic method as explicated by Organic Gardening magazine, we have much to learn. Solomon isn’t knocking organic gardening methods; rather, he wants to extend them to take into account what has been learned by soil chemists and successful holistic farmers about the need for and practice of re-mineralizing farm soils. Soils need re-mineralization because they are leached by rainfall and because typical agricultural, horticultural, and landscaping practices (even organic practices) remove some of the soil’s mineral reserves without replacing them and may create excesses in some minerals that are harmful to crops. Crops grown on such soils will not be as nutritious as they could and should be to sustain their own health against disease and insect attack. Since they lack nutrition, they cannot create the proper level of health in those of us who eat them.
The good news is that we can gradually replace the missing minerals in our soils and reduce excessive levels where those occur; Solomon’s book tells us how to do both. For those of us who don’t have the inclination to have our soil tested, Solomon offers an updated version of his complete organic fertilizer recipe. It’s not quite as simple to prepare as his earlier recipe because his research has led him to tweak the mixture depending on where you live, but it should also work a little better than the version in his earlier book. For those of us who want to develop a mix better attuned to our particular soil, Solomon tells us how to collect a soil sample, where to send it to for analysis, and how to interpret the results and use them to develop a mix tailored to remedy the particular pattern of deficiencies and excesses our own soil exhibits. I’ll be doing this and will report on what I learn, the mix I develop, and its effect on my garden throughout the season. I encourage other gardeners to read the book and try the updated recipe (or, if you want a personalized mix, have your soil tested and develop your own mix and try that). Let me know how it works for you. I’ll be interested in comparing results with those of you who have the more clayey soil typical of most of the St. Louis region rather than the silt-loam loess soil that I have.