Home Composting – How to Use Compost
How to Use Your Compost
You can probably always find a use for. How and when you use it depends on what your garden needs, the characteristics of your , and on the state of the compost. The point of is to recycle fertility that has come from the soil, back into the soil, so using compost gives your garden a boost when it needs it, and promotes long-term health.
Mature compost should be dark brown, soft and crumbly. It may not be perfectly even textured, as some bits may not have decomposed as thoroughly as others, but this doesn’t matter. You can pull them out or ignore them, depending on the compost’s destination. Some gardeners say that slow composting produces the best compost, others swear by hot (see how to choose the best home composting method). The end results should be similar, but compost that has been made very quickly, as in a commercial tumbler, is best left to stabilise by leaving it covered for a month or so before use.
Digging or leaving?
It is not a good idea to dig your soil too much. If you give it a thorough overhaul when you take over a garden or prepare new beds you shouldn’t need to dig at all, unless you want to. Every time you tread on the soil you compact it a little, and digging can harm a fragile structure. This is why many gardeners use compost as a general fertility mulch instead of digging it in wholesale. As a rule, whenever you dig or turn the soil — to clear a patch of ground, to make planting holes for perennials, shrubs and trees, or trenches for vegetables — add a generous amount of compost as you backfill, otherwise leave it on the surface for worms and other soil organisms to drag down. You should then only need to scratch over the surface with a fork before further sowing or planting.
Where to Use Your Compost
Try to apply about 2 cm of well-rotted compost to your soil each year as a general soil fertiliser and conditioner. Use the compost as a mulch or fork it lightly into the soil in spring and summer. In established herbaceous beds, you can spread compost around plants in spring or autumn.
Compost made in a tumbler is best stored to mature for a few weeks before use, otherwise it is rare to have to store compost. Most compost is ready for use as soon as it has decomposed, although it will not pass on nutrients to plants for another couple of weeks when the soil microbes have got to work.
It is always better to use compost when it’s available rather than store it for a long time because the nutrients within it can be leached out of a standing heap. Also, a long-standing compost heap can turn anaerobic if it gets too wet.
Always store compost on the earth, so any nutrients that do leach away go straight into the soil, and cover it with a thick layer of soil, or carpet or rotting straw. Use it within six months.
Before you plant, prepare your soil by adding compost to provide nutrients slowly when plants need them. If you have well-rotted compost lay a 5cm mulch over clay soil in autumn, and plant through that in spring.
You can leave a winter mulch of semi-rotted compost over sandy soils to break down over winter, and then fork it into the soil in the following spring. Or fork well-rotted compost lightly into sandy soil in spring about four weeks before planting.
Mix compost with topsoil whenever you plant a herbaceous perennial, shrub or tree. Mix the compost into the bottom of a trench before planting, for example,and celery. Potatoes can get scabby if the compost is not well-rotted.
Acid-loving plants appreciate slightly acid compost, or add a layer of chopped leaves or semi-rotted pine needles with the compost when planting strawberries or acid-loving shrubs.
Fork compost into a seed bed, or incorporate overwintering compost mulch three or four weeks before. Be sure it is well rotted as unfinished compost can sometimes retard seed germination.
Some gardeners choose never to dig their soil. Instead, they prefer to add 5-10cm layers of compost annually or biannually. All sowing and planting takes place through the compost.
Where perennial plants are growing in containers, you can rejuvenate the soil each autumn by scratching off the top few centimetres and then replacing it with fresh compost. Lawn-proud gardeners can use finely screened compost as a top dressing in autumn.
Compost tea makes an excellent pick-me-up for any tired plants, or as a boost to water or potted plants.
Can You Add Too Much Compost?
Test the pH of your compost with a kit from a garden centre. Neutral pH is 7, anything below is acid (not enough lime), and anything above is alkaline (too much lime).
Healthy topsoil should be around 10 per cent organic matter. This may not sound very high but when you add well-rotted balanced compost to a receptive soil it gets incorporated without adding greatly to the overall percentage, so it is hard to add too much. But there are situations when you can get it wrong. It depends what your compost is made from, what your soil and climate is like, and what you intend to grow.
Balancing the diet
If you always use the same materials in your compost heap you can eventually overload the soil with some elements. If your compost is too nitrogen-rich you’ll encourage sappy and leafy growth at the expense of rooting and fruiting. If you use too much fibrous material you could starve the soil of nitrogen.
If you are worried that you are adding too much of the same materials to your compost heap, you can always add some plants such as horsetail to vary the home composting recipe.
Instead of buffering your soil’s pH, you can make your soil less hospitable — for example if you make very acidic compost. If you are composting large amounts of garden waste, and your soil tends to be rather acidic, your compost will be increasingly acidic so you must be sure to add lime to your heap.
If your soil needs regular liming, your compost heap will also need regular additions for balance. If your soil is (more rarely) too alkaline, you may need to add powdered gypsum or sulphur to your pile.