Only a healthy garden soil is able to meet the climatic challenges that arise with climate change. In this topic you learn about the structure of the soil of the garden and what is the finger-test; what are the conditions needed for a vital soil structure and what garden implements you need for careful tillage and weeding.
Soil protection:
Especially when gardening, it is essential to pay attention to the soil and to work adapted to the climatic conditions. Heat, drought and heavy rainfall are becoming ever greater challenges and only a healthy garden soil is able to meet these challenges because of its structure and vitality and can optimally supply the plant with water and nutrients. If the soil is used too carelessly, this has a variety of consequences. These range from ecological to economic, social and health challenges.
Ecological impacts: Loss of biodiversity and natural soil functions.
Economic impacts: Loss of productivity and food security, high infrastructure costs, and increased natural hazard risk (flooding) if soil is sealed.
Social impacts: Urban sprawl and uneven distribution of land among different social classes.
Health impacts: Heat and fine dust pollution, loss of nature’s recreational function.
Soil cultivation
Careful soil cultivation can do much to maintain a healthy and fertile soil with a loose and crumbly structure in the garden. Only then oxygen, water and nutrients can be stored in the soil, which in turn has a positive effect on soil organisms and prevents erosion and stagnation of water.
Advice for gentle soil cultivation in the community garden:
-Know your own ground:
First of all, it is essential to get to know one’s own soil. This is because different soil types make different demands on soil cultivation or react differently to it. A first simple classification can be done directly on site in the community garden.
Experience soil with 4 senses:
- Listen: Take a little bit of soil, hold it in front of your ear and squeeze! A soil rich in sand crunches.
- Taste: You can also taste soil – sandy soil feels unpleasant and rough in the mouth. Clayey soil, on the other hand, feels unctuous.
- See: The darker the soil, the higher it is: The darker the soil, the higher the humus content.
- Feel: → “Finger test”
With the “finger test”, a rough classification of the soil type can be made. The soil type is determined by the mixing ratio of the mineral components of sand, silt and clay (see Topic 1).
How to do the “finger test”
What is needed:
- 1 scoop or spade
- Bowl or base for storing/lying on the sample
- Water for moistening the soil sample (possibly in a spray bottle)
First step:
Take a soil sample about the size of a walnut with the shovel. If the sample is very dry, moisten it a little. The sample should be shiny, but no water should come out when it is crushed.
1. Feel the granularity: grind the sample between thumb and index finger and determine the granularity (see table).
2. Determine formability and kneadability: Try to shape the soil into a pencil-thick roll with the palms of your hands or on a smooth surface. Also pay attention to the level of soiling of the hands!
3. Visibility: If the individual grains are visible to the naked eye, then sand is present. If fine dust sticks to the finger grooves, then it contains silt. If the soil is very dark, then the humus content is high.
Analysis of the soil sample
- Soil sample can be rolled out → The soil belongs to the group of loamy to clayey soils.
- Soil sample can be rolled out once, but crumbles when rolled out again → this soil has a large silt content.
- Soil sample disintegrates when rolled out → The soil belongs to the sandy soil group.
Sand feels rough and grainy. It does not stick in the grooves of the fingers -> no dirt on the hand. The individual grains are clearly visible. (Grain size between 63 µm and 2mm).
Silt feels velvety-floury and is hardly cohesive. If you crumple silt, the surface is not glossy. Silt adheres strongly in the finger grooves. Silt grains are so small that they are not visible to the naked eye or magnifying glass. (Grain size between 2 µm and 63 µm).
Clay feels sticky and is very cohesive. That is why it is easy to shape. When clay is crumpled, it produces a glossy surface. (Grain size smaller than 2 µm).
Good to know:
Loam is a mixture of these three components: Clay, silt and sand. Grain sizes are difficult to feel, as clay feels both grainy as well as velvety and greasy.
Choice of Garden implements
So that the biological activity of the lowest level of the soil is not disrupted, the soil shouldn’t be worked loose. Turning the soil is only necessary, if heavy soil is occurring or a new garden patch is placed. The loosening up of the top of the soil you should do manually with tools like a hand-grubber, a claw, or a digging fork. It’s best to work the soil loose with the digging fork and not to dig it up with a spade. Also for weeding you need an appropriate implement such as a heel or weeder. Crucial is the timing: If you can remove unwanted plants soon and regularly, then the plants can’t be spread out by seeds or roots throughout the whole garden.
Avoidance of soil compaction
The best protection against soil compaction is the avoidance of heavy machines and tools, and of intensive methods of tillage, especially on wet grounds. Only by this way can you prevent soil pores being more and more compressed. Also the time of tillage is important: it should occur during dry conditions, because the soil structure is destroyed during wet conditions. Here you can use the finger test as well.
Stimulation of soil organisms
For a loose and crumbly structure of soil the stimulation and preservation of soil organisms is crucial. It can be developed by a variable crop rotation and addition of organic material such as compost and green manure. Moreover it is important not to withdraw nutrients one-sided during the garden year.
Soil improvement in the community garden
Improvement of the soil structure:
by soil loosening: Within heavy soils or grounds with a disrupted soil surface air is introduced into the soil so that the provision with water and nutrients gets improved. For loam and clay soils the addition of sand also helps. The loosening should only worked up during dry conditions.
by plants/ green manure: So as to improve the soil before the actual planting, you can sow green manure. Therefore the soil becomes loosened, also by the developed roots, and the biological activity becomes stimulated.
Regulation of the pH-value
If the pH-Value of the soil is to high (alkaline) you can regulate it by adding bark humus. Too low pH-value (acidic) can be improved by adding lime (calcium). Advice: every chalky soil is alkaline.
Bibliography:
Forum Umweltbildung: FUB_Bodenschutz_Materialien_UA.pdf, 16.06.2023
Österreichische Bodenkundliche Gesellschaft: ÖBG – Österreichische Bodenkundliche Gesellschaft – Bodenart (oebg.org); fingerprobe_final.pdf (2 MB), 06.06.2023
www.ages.at: Fingerprobe.pdf (ages.at), 06.06.2023
Umwelt-Bildungszentrum-Steiermark: Natur / Lebensräume – UBZ, 06.06.2023