I’ve just been reading Soil Science Simplified’ target=_blank>“Soil Science Simplified” by Kohnke & Franzmeier and that reminded me of some insight that I now take for granted, but which was originally one of those ‘blinding flash of light’ moments for me.

On the second page, they point out that “A green plant is made up of about 80% water and 20% dry matter. The largest part of the dry matter is composed of the elements hydrogen, oxygen, carbon and nitrogen which occur in air and water, while the rest consists of a great variety of elements that originate in the soil. In spite of the small amounts of these components, they are absolutely essential and the complete absence of only one of them makes plant growth impossible.”

Buried in that paragraph is a nugget of information that is vital to the organic grower: the essential nature of trace minerals.

Trees, like any other plant, generally take up only the nutrients they can use and they do so in the precise ratios needed for growth. The proof of this is that these ratios DID result in growth.

Tree leaves are abundant now in many locations around the world and they represent an incredible storehouse of those trace minerals brought from deep below ground in an easy to collect and use form. This isn’t rocket science, folks, the trace minerals have already been mixed and proportioned and packaged for you. The brain part is done: now all that is needed is a little grunt work.

Although there are a number of subtle shadings about how to use them, let’s look at just a couple: decomposition in situ and decomposing before incorporation.

Firstly, let’s tackle ‘in situ’. All this means is to mulch the leaves directly into your lawn, to dig them into your garden or to layer them on top of the soil so as to provide a blanket over it. This will use a goodly number of leaves and is a recommended practice. A mulching mower set to a low cutting height is ideal for the task of mulching leaves into the sod, as the grass should in any case be cut short this time of year to avoid fungal diseases over the winter. The less green you see, the fewer sugars to tempt snow mold and other fungi.

The second general manner of using tree leaves is to decompose them somewhere other than the point of final use. You might want to finish off a compost pile begun earlier in the year by turning leaves in to it, mixing them thoroughly as you do to prevent them from forming a water-shedding layer. You might also take a tip from others and, after shredding them somewhat with a mower, stack them against a fence or other structure to allow them to begin decomposing there. To the extent that weather permits, earthworms will gladly turn the bottom layers into something called “leaf mold”, which makes an excellent mulch or soil amendment in the spring. Also, in the spring, you can use the dried top layers as the initial ‘browns’ charge for a fresh compost pile.

Fall is also important because soil amendments applied now … lime, bone meal, sulphur, green sand, compost and so on, will have time to be incorporated into the root zone before spring planting. This allows the moderating influences of chemistry (organic chemistry can be gosh-awful slow) and microbiota to be felt, leaving the soil in a more ‘settled’ state. For instance, adding lime or sulphur will change the soil pH (that’s generally WHY they are added) and that will cause distress for the biota that thrived at one extreme or the other. Having winter to work in allows the other biota favoring the new pH to re-establish themselves. You want your soil fully populated by the time it is warm enough to plant. Applying amendments in the fall assists in that goal.

Now is the time to discard leftover plant parts. If the plant simply died because of the cold, it can be sent to the compost. If it died because of disease, send it straight to the trash hopper. Compost cures a lot of stuff but if you add diseased plant material to a late-fall pile, it may never get hot enough long enough to sterilize the pathogens. In that case, you need to allow the pile at least one, and preferably two, years to sit and mature.

Unless beans, peas or other legumes died from disease, do not pull them up by the roots. Rather, cut them off at the soil surface so as to leave their rhizomes in the ground. A quick flick with a sharp hoe will do the trick as will running over them with the mower if you have planted alfalfa or buckwheat and intend to use the top portions as green manure.

Look for some quotes from Kohnke & Franzmeier’s book in the sidebar. I’m liking what I see.