Page 12 - ALG Issue 3 2023

hot topic
National Allotments Week
2023 is all about
‘Soil Health’
2023 marks the 21st year of National Allotments Week.
This year, National Allotments Week will run from 7th – 13th August with the theme of Soil Health, and there is lots to look forward to.
Leading proponent of the ‘No Dig’ movement, Charles Dowding, will be joining the NAS during the week to share his wisdom on how to create healthier soil and better crops.
The no dig method is used by many plotholders to increase the biodiversity and health of their soil through mulching and layering techniques.
Good soil health is widely accepted as a way to improve yield when growing edibles, but also contributes positively to biodiversity and the environment as the world faces more climate challenges.
HOW CAN YOU IMPROVE YOUR ‘SOIL HEALTH’?
Fortunately, improving soil health is similar whatever the symptom or cause of poor soil health: Adding more organic matter solves most soil problems.
The best way to add organic matter
is as mulch: simply spreading organic matter on top of the soil. Mulch on the soil surface will be eaten and taken below the soil surface by worms and microscopic animals/bacteria, who break organic matter down to produce humus. This process releases minerals that plant roots can absorb.
Organic matter takes many forms and which you choose to use comes down to personal choice and availability. For example, animal manure can be difficult to obtain in some urban locations,
or plot-holders may wish to avoid potential issues with animal manure contaminants such as Aminopyralid (a weedkiller sometimes found in animal manure), and some plot holders avoid
animal manures for ethical reasons (Veganic gardeners). Alternatives to animal manures include composted kitchen and garden waste, green manures, and well-rotted woodchips. See Sources of Further Information.
6 PRINCIPLES OF SOIL HEALTH
1. Increase organic matter
2. Cover the soil, so it is not exposed
3. Minimise soil disturbance (see No-Dig Gardening)
4. Reduce pesticide/fungicide use
5. Grow a diverse selection of plants
6. Avoid compaction by heavy machinery and feet
MINERALS
Plants need many different minerals (e.g. magnesium, potassium, nitrogen) to grow well and a healthy soil will provide these in balance. Unhealthy soils may lack some minerals or the minerals may be out of balance. Some minerals dissolve in water and so easily enter the soil to keep it healthy, as well as being taken up by plant roots to
help them grow well. However, some minerals do not dissolve in water, this is called being “locked up”. Help is at hand from a useful group of beneficial fungi which “unlock” minerals to improve soil health. This group is called Mycorrhizae and can also help to boost plant growth.
MYCORRHIZAE
Mycorrhizae are beneficial fungi that live in the soil. They thrive on plant roots and may superficially look like a disease but they are doing good. Mycorrhizae can be seen with the naked eye on the roots of some plants, e.g. beans and peas, however, most are microscopic. Mycorrhizae access soil minerals that plant roots are not able to reach or dissolve on their own. Healthy soil
will have plenty of mycorrhizae, but if your soil lacks these fungi you can buy powdered preparations which may help.
Good soil health is widely accepted as a way to improve yield when growing edibles
NITROGEN AND NITRATE
The plants on your plot need nitrogen to grow and thrive. Nitrogen is one
of the most important minerals for living things and is needed for DNA and proteins in every cell. Plants get their nitrogen from soil nitrate, which bacteria and fungi release when
they decompose organic matter. Unfortunately, nitrate is highly soluble in water, so heavy rain will remove it. This also causes pollution in waterways (leaching). Keeping a healthy level of nitrate in the soil without leaching is very important for your soil health and plants. A healthy soil full of hummus and oxygen will hold onto nitrates better than unhealthy soil that is compacted and lacks organic matter.
OXYGEN
Healthy soil needs oxygen just like our bodies do. Plant roots need oxygen to stay alive, as do all the animals, fungi, and most bacteria living in the soil on your plot. Soil becomes unhealthy when oxygen is depleted, e.g. when soil is waterlogged from rain or compacted
by walking on it. Healthy soil is loose, friable and has plenty of oxygen. However, some species of bacteria (anaerobic) can live without oxygen and these tend to be bad for crops, nutrients and soil health. These bacteria thrive
in waterlogged and/or compacted soil. Avoid walking on your growing areas as this compacts soil. Laying wooden boards on the soil surface while you work can help reduce compaction as
12 Allotment and Leisure Gardener