Green Manures: Why Don’t We Learn From Old Wisdom?

clover green manure crop nutrients soil leguminous nitrogen-fixing
Above: clover, a common nitrogen-fixing green manure crop used to return nutrients to the soil

Approaching a new plot of land is a daunting matter. Particularly in London. I have heard of people uncovering mattresses, televisions, and all manner of things lodged deep in this damp, clay soil.

Sadly, at a time when ‘vintage’ remains vogue, I doubt I am going to uncover any butler sinks any time soon. A shame, as they are lovely things in which to grow more vigorous species, like mint and nasturtiums.

The garden to which I’m tending this year is less than ten years old. The soil, whilst full of happy, healthy worms and traces of mycorrhiza (the parts of mushrooms we don’t tend to see), is very clay, clumpy, and generally in need of a lot of love. I can see where the garden is trying to come into its own, and have observed which species are doing well, but it could still do with a helping hand when it comes to building the soil.

It is no accident that we are starting to pay more attention to our soils and the way that we grow our crops, at a time when we are having to refine our growing and farming practices to meet the demands of burgeoning populations and climate change.  We are only just beginning to examine soil composition and its flora and fauna in earnest, and it is perhaps our increased understanding of these relationships that has led to zero-till and no-dig methods gaining popularity. Both are topics that I will examine in future.

In my own garden, I am going to be using ‘green manures’ to build up the quality of the soil. The Royal Horticultural Society defines green manures as “fast-growing plants sown to cover bare soil. Often used in the vegetable garden, their foliage smothers weeds and their roots prevent soil erosion. When dug into the ground while still green, they return valuable nutrients to the soil and improve soil structure”. Often, these plants are nitrogen-fixing, e.g. leguminous, like clover, and take nutrients from the air, store them in their roots, and bring nutrients back to the soil.

Such practice is nothing new. The tendency to keep fallow fields is almost as old as farming itself, and is a necessary part of returning nutrients to the soil. Intensive methods have all but forgotten this wisdom, and mean that soils are left monocultured and bare – practices as bad for the soil as they are for the ecosystems that depend on it.

Country Gentleman 1853 Cover Journal Agriculture
Above: cover page of ‘The Country Gentleman’, a Victorian-era American agricultural and horticultural publication featuring the latest news and advice on scientific method, technology, and philosophy.

Here is a lovely letter I discovered from a Pennsylvanian farmer describing his process of using green manures to improve his crops. The letter comes from an 1853 farming journal, ‘The Country Gentleman’. It is available from the British Library, should you wish to peruse it for yourself.

“Mr Tucker — I see in the last number of your Cultivator, some person inquires of you about sowing clover among corn, and as it is a common practice here, and our manner of doing it appears to be somewhat different from yours,  I thought I would give you a brief account of it. As our oat crop here brings but a poor price, and is generally considered to be an exhausting one to our soil, a number of our farmers have ceased raising it, and instead of following our corn crops with an oat crop, as was our usual rotation here, we now always sow our corn fields with clover seed. We always sow it just after the double-shovel plow runs through our corn the last time. I sowed my seed this summer, in the first week of July, and and the corn field now looks fine and green, with a good coat of clover on it. A neighbor of mine has now one of the finest looking clover fields, done in the same way, that I have ever seen. I did the same thing last year, and the year before. It affords early pasture in the spring following, and then the cattle are kept off until after the harvest, when it has grown up considerably, and is then turned under for wheat. I never turned under better clover than I did this fall, that was sowed in among my corn last summer a year. Of course, we do not sow it as thick as if we would want to keep it for mowing or permanent pasture. We consider that it pays us much better in the way of pasture, and then in a manure for wheat, than the ordinary oat crop would after our corn. We seldom fail here in getting it to catch, unless the season is unusually dry, and then it partially fails.

We always sow it immediately after a rain, or directly after the plow, while the ground is fresh and mellow, and it will then start at once, and if the drouth [sic] does not kill it, you will have a fine crop of clover. A PLAIN FARMER. Franklin Co., Penn.”

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