Every spring the question arises again: can I use the old potting soil again? This could save costs, because new potting soil is not cheap, depending on the quality.
Used potting soil can be improved and reused
components of the potting soil
Fresh potting soil consists, among other things, of fresh compost, peat or other fibrous materials, as well as a depot of long-term fertilizer. The soil is loose and crumbly, it has a good stability of its structure. This is important so that the cultivated plants can find a footing and do not fall over at the slightest gust of wind.
In addition to the fibers, clay granules or perlite (granules made of volcanic glass) (granules made of volcanic glass) are also included to store water. Additions of sand make the soil permeable so that no waterlogging can occur.
The used potting soil
If plants have already been cultivated in the soil for a season, the soil will have collapsed and become firm. You lack nutrients, the fertilizer depot is used up. If the soil is used for another planting in this condition, the roots will no longer get enough oxygen and they will no longer be able to supply the plant with nutrients.
Therefore, a used potting soil must be prepared in any case.
It is best to use the following options:
- aerate and loosen the soil well by working it mechanically with a digging fork or hoe
- Work in compost or good garden soil
- Bark humus and wool fertilizer also ensure ventilation
- in the garden bed or planter, the soil can be loosened with green manure (phacelia, mustard seed, lupine), which is dug under in the spring
- incorporate new long-term fertilizer in the form of horn shavings (32.93€) sheep's wool or horse manure pellets, it maintains soil life
- Always add one or two handfuls of compost to pure nitrogen fertilizer such as horn meal
Depending on which plants are to be cultivated in the prepared soil, the amount of fertilizer must be individually adjusted:
- Weak feeders such as radishes and peas require little or no new fertilizer
- for medium feeders like carrots and spinach, add about a handful of fertilizer to 20 liters of soil
- Heavy feeders like potatoes and tomatoes need two handfuls of fertilizer in 20 liters of soil
If the potting soil is too depleted, completely stuck together and heavy from unexpired water, don't throw it in the trash. It goes on the compost heap and is renewed there by the soil organisms.