Today, with a nod to my ancestors, I’m going to spread dark green flakes over some of my vegetable beds and beneath some fruit trees and bushes. That nod is not to my ancestors that came here from Poland, Austria, and Argentina, not even further back into the reaches of humanity from the savannahs of Africa. No, I’m referencing my – all of our – ancestors that first crept or waddled forth from the seas.
The dark, green flakes are kelp, a kind of seaweed; if the sea nourished our flippered progenitors, I figure it might also provide something nutritive to today’s iPod-appendaged humans. Kelp is rich in a grand array of trace minerals, many of which are known and some of which may become known as necessary to maintain health. So I’m spreading this stuff on my soil where its goodness can work itself up into my edible plants and, hence, my diet.
Spreading kelp here may be akin to “hauling coals to Newcastle.” After all, the ground in my vegetable beds has been beefed up over the years by annual dressings of compost an inch or two thick. Into that compost went not only all waste from my gardens and kitchen, but also manure, wood chips, and leaves that I’ve imported. Which is to say that my soil probably is already replete with a rich array of nutrients for my plants and me.
Years ago, I supplemented those compost applications with soybean meal. Soybean meal is high in nitrogen (7percent), which I figured would be the only nutrient my intensively planted vegetables might need. I also figured - literally - that a one inch depth of compost could supply all the nitrogen my vegetable plants might need, even if intensively planted, but couldn’t bring myself to really believe that calculation. Finally, a few years ago, I walked my talk, and ever since have been doing nothing more to the soil in my vegetable beds but slathering it an inch deep in compost every year. And the vegetable plants have been as happy and healthy as ever.
Fruit trees, shrubs, and vines also get compost, in their youth. After that, mulch supplies most of their nutrient needs. I and my fruit plants are not finicky about what kind of mulch it is: sometimes it’s wood chips (courtesy of local arborists), sometimes it’s autumn leaves (courtesy of my neighbors), and sometimes it’s hay (scythed from my one acre field), according to my whim and what’s available. These mulches have many benefits beyond nutritive. They improve percolation of rainfall into the soil, they help soil hold water and improve aeration, they feed the soil food web, and they break down to add humus to the soil which, in turn, helps release and make more available nutrients already in the soil. In poor soil, it may take more than mulch to feed trees, shrubs, and vines, in which case a sprinkling of soybean meal can tide the plants over for a few years.
I like soybean meal because it’s simple to use. One feeding per year is all that’s needed (if it’s needed at all). Moisture and warmth spur its decomposition and release of nutrients as well as plant growth, so everything’s in synch. Other seed meals and alfalfa meal would work equally as well, but they’re more expensive.
(Contrary to what some people believe and write, high carbon materials, such as wood chips, will not “rob” plants of nitrogen when used as a mulch. Laid on top of the ground, these materials break down very slowly, at the interface of the soil and the mulch. A steady state condition exists, then, where nitrogen is re-released into the soil at about the same rate is it is “robbed.” Mixed into the soil, though, high carbon materials will rob plants of nitrogen, albeit temporarily.)
Emblazoned on bags or boxes of commercial fertilizers, organic and not, are three prominent numbers (such as 10-10-10 or 5-10-5) indicating the amounts of nitrogen, phosphorus, and potassium - NPK, for short - they offer. Nitrogen, phosphorus, and potassium are macronutrients, needed in relatively large amounts by plants and humans.
Kelp supplies little of those major nutrients. Still, fish, humans, and everything in between, need much of what kelp has to offer. An array of organic materials, including compost, wood chips, leaves, and hay, probably also offer those other nutrients that we all need. Just to make sure, every few years, I sprinkle some kelp on the ground. A mere one pound per hundred square feet should do the trick.
Lee Reich describes the weekly goings-on at his farmden (more than a garden, less than a farm) at www.leereich.blogspot.com.