|Posted on 5 July, 2016 at 4:15|
The importance of organic matter in the soil cannot be overestimated. It plays a role of enormous significance, not simply by helping to control sharp fluctuations in soil temperature, but acting as a kind of sponge and helping the soil hold moisture...
Organic matter also acts as a kind of larder for various minerals and other plant foods, allowing the plants to absorb their requirements in a gentle way. So, the question is: which is the best way to incorporate this important ingredient into our garden soils?
The simplest and easiest way is to spread half-decayed plant matter such as lawn clippings, wilted weeds, leaves, old straw and spoilt hay over the surface, as a mulch, and let the worms and other soil creatures do the job of gradually taking it down. It is staggering to see the speed with which earthworms deal with a layer of organic matter. One week the surface is strewn with a thick, healthy layer and a week or so later, bare patches start to appear. Before long the whole surface needs to be replenished.
The interesting thing about the role of worms is that the more organic materials available on the surface, the more the worms will multiply in the soil. Gardens without worms are invariably gardens with little organic matter in the soil. Digging plant wastes into the soil can be a bit tricky. If the material happens to be a little woody or coarse, the effect of the soil's micro-organisms trying to break it down can actually produce a serious deficiency of nitrogen. The worst cases I have ever seen occurred when people incorrectly dug sawdust or seaweed into the ground. The effect of this subsequent nitrogen deficiency was un-thrifty growth of plants, with a poor, pale leaf colour.
This is the ideal time of the year to enrich the soil ina special way. Green manure crops can go in now as seed, so that later on the resultant growth can be cultivated into the soil. Digging in this raw organic matter will not cause nitrogen deficiency problems because, being green and lush, it contains good quantities of this element, plus many more. It must seem odd to many people, to actually grow something to a certain stage and then dig it in. The secret is that this process is carried out before the 'winter-tares', as they are called, have started to form their seed and become a bit woody.
The traditional seeds for people to sow at this time, for green manure, have been Algerian oats and tickbeans. These provide good quantities of excellent organic matter and plenty of nitrogen, especially from the legume. Blue lupins too are used as a good source of nitrogen.
The other advantage of these winter crops is that they occupy and grow strongly in cool, wet soil. They keep the soil active and sweet, while the density of the planting also helps to supress weed growth.