In the wild a plant grows, taking nutrients from the soil, then dies back, and aided by worms, insects, and bacteria the rotted plant returns those nutrients to the soil so that they can be used again by other plants. In cultivation, and especially in the vegetable and fruit garden, this balanced cycle is broken because we harvest the plants and tidy up the garden by removing dead material. We therefore need to replace the naturally rotted organic matter each year by digging in manure or garden compost.
Apart from supplying food for the growing plants, digging in organic matter improves the soil’s structure. Worms, insects and beneficial bacteria are attracted by the supply of food and multiply. Worms and insects improve the aeration of the soil by burrowing; in addition, worms provide fertilizer in the form of worm casts. Some bacteria help in the process of decay while others fix nitrogen from the air into the soil.
Bulky organic matter also helps to turn clay particles into larger crumbs and holds these crumbs apart so that drainage will be improved. It also coats the particles of sand so that the water drains less easily.
The manure provided by herbivores is an excellent soil conditioner. Contact local stables for supplies of horse manure, which is better if it is based on straw bedding rather than wood shavings. Cow manure is not as readily available as it used to he as a result of current cattle-rearing methods. If you live in the country look for a local Farmer who turns out his cattle in the summer in the hope that he has supplies to spare at the end of the winter. Sheep manure is high in nutrients so if you live near a sheep farm ask the farmer if you can collect it off the fields. Pig manure is also high in nutrients and chicken manure is very rich.
Do not use fresh animal manure on the garden. It needs to rot down completely first as in the fresh state it can burn plant leaves and stems, and the decomposing straw it contains will use up nitrogen in the soil.
Mustard is quick-growing green manure, which is dug into the soil before flowering to provide nutrients and improve the soil’s structure. If you have an empty bed, especially if your soil is light and free draining, it is better to sow a green manure like mustard, winter tare or red clover than leave the soil bare when rain can destroy the structure, nutrients drain away and weeds start to grow. Although the growing plants remove some nutrients, when dug back they provide more. As an alternative to digging the plants back into the soil they can he chopped off and left on the surface to be incorporated when they have decayed.
A very good source of bulky organic material, free to us all, is household and garden vegetable waste. This again needs to decompose before it can be added to the soil. A compost container not only looks tidy hut it speeds up decomposition by keeping the material warm. You can simply pile the material in a heap hut it will take longer to rot down.