Hortisol – fruitful garden soil

For newcomers to cultivating a vegetable garden, the first challenge they face is a big one: how to transform land into crop land. And how to produce fruitful garden soil. Let's start with the bad news: getting started takes money, time and energy. But the good news is that it gets easier with each passing year, provided you employ organic gardening methods: then the humus content increases from year to year, making gardening easier as time goes on. The best way to quickly transform poor soil into a fruitful garden bed? Building a raised bed.

An almost 80-year old passionate gardener recently told me that it takes 30 years to produce good garden soil, that you need to garden for 30 years – organically! – to get the garden soil to where it is really good. 30 years - that's almost half a lifetime! I was thinking about that and what I should write in this article as I was taking our dog on her daily walk early one morning. Our walk took us past a number of houses, with a large fresh pile of dark, fruitful soil on one plot. I wondered what was happening and continued on. At one house was a digger. There was a big hole where a vegetable garden had stood for many years. The house and garden owner, a neighbour, was out working. I asked him whether he was building a new garden. "No", he said, his son wanted a swimming pool. I couldn't help but be surprised: while I keep getting people contacting me asking how to cultivate a self-sufficient garden and how to turn land into fertile garden land, here was someone deciding to turn his fruitful garden land into an – unfruitful – pool.

What is fruitful garden soil?
The German soil classification has its own soil type – incidentally the only one to be artificially created – the garden soil Hortisol. Hortisols do not occur in "outdoor" nature untouched by man, but rather are produced in the – for geologists – short period of 200 to 300 years. Even if my neighbour's garden was not real hortisol – because there had "only" been a garden there for 30 years – the soil had already changed during this time and had a higher humus content than before. True hortisols range in colour from dark brown to almost black because of their high humus content. They have a humus horizon more than 40 centimetres deep, produced as a result of the deep horticultural tilling and the intensive addition of humus.

Compost – the secret to fruitful soil
The only way to produce fruitful soil is by regularly adding good compost or manure. On the one hand this fertilises the plants cultivated this year and on the other adds organic matter to the soil, which is converted into permanent humus by organisms in the soil. Permanent humus is the goal of every gardener because it can hold almost twice its own weight in water and bind nutrients and keep them ready for the plants. Soils with a high humus content are crumbly and loose and the plants can root well in it. Us gardeners like it because the plants grow healthily and abundantly and the biological balance in the soil prevents the rapid spread of soil-borne plant diseases. A recent study by the Vienna University of Natural Resources and Applied Life Sciences even proved that soils with a higher humus content are less likely to have slug infestations.

Is there a way to speed up the process?
If you don't want to wait 30 years, the next best approach is to plant a raised bed. However, this is quite costly during the first year because a lot of organic matter needs to be added. Raised beds take a few years to become established, but can then be cultivated like normal garden beds and also provide a quick way of transforming compacted soils into fruitful vegetable beds, for example after building a new house.

Instructions for building a raised bed
Start by digging out the humus layer to a depth of approximately 20 centimetres in a patch 150 cm wide and however long you want. Then line the excavated cavity with fine-mesh wire to keep out voles and other small animals. In the middle of the new bed, pile up the "core" of coarsely shredded branches and clippings from trees and hedges to a depth of 40 to 50 cm and a width of 70 centimetres. Then comes a 15 cm layer of grass turf (with the turf pointing downwards) or alternatively straw chaff with manure or fresh kitchen waste – you can also build a raised bed in autumn and throw all the kitchen waste over the winter into it. This is followed by a layer approximately 30 cm deep of wet leaves. On top of this is a layer approximately 20 cm deep of fresh, unrotted rough compost mixed with some silicate rock dust. The raised bed is then topped with approximately 20 cm of a mixture of the dug-out garden soil and 20% mature compost.

Andrea Heistinger
VIKING gardening expert

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