What is soil?

What is Soil?

Soil is an incredible material. It is said that one handful of soil contains more life than there are humans on Earth. Soil is bursting with life, making it one of the most complex ecosystems on our planet.

Home to nematodes, protozoa, bacteria, fungi and a whole host of insects, all of these organisms support healthy plant life; meaning if we look after our soil, it will look after us.

While soil is highly complex, in practice it's actually really simple to look after.

Different Types of Soil

There are three main types of soil: clay, silt and sand. In order to find out which type you have in your space, you need to get your hands dirty.

Take a handful of your soil and try to roll it into a ball. Clay soil – which is made up of tiny particles – will form a ball easily, whereas sandy soil, which is made of larger particles, will not. Silty soils lie somewhere in between.

If and when you have a ball, try and roll it out into a sausage shape and then see if it will bend. Heavy clay soils will bend and hold their shape, whereas sandy soils will fall to pieces.

Sandy Soil

Sandy soils are less nutrient rich than the other soil types and can be prone to dryness as they are so free draining. Understanding that you have this type of soil will help to influence your planting plan. For instance, lavender is a great choice for sandy soils, as it isn't nutrient hungry and it likes a free-draining environment.

Clay and Silty Soils

Clay and silty soils tend to be nutrient rich and retain water well, but due to their small particles, they can be prone to compaction. However, this generally only happens when there's been too much footfall on the soil or heavy machinery has been used on it in wet weather.

Compaction can lead to poor water movement through the soil, resulting in water gathering on the surface. Brassicas like cabbages, kales or Brussels sprouts do well in clay soil as they like their roots to be firmly anchored. Squashes do well in clay too, they are hungry plants so enjoy the higher nutrient level.

Soil pH Level

The acidity or alkalinity of soil also informs the plants we can grow in it. For instance, ericaceous plants, such as blueberries and cranberries, will only thrive in acidic soils, whereas plants like brassicas will thrive in the alkaline soils usually found in chalk and limestone areas.

Whatever soil type you have, the best way to improve it is by adding organic matter.

List of Indicator Plants for Different Soil Types

You will get a better understanding of a space by observing plant communities rather than single plants. For example, one wild carrot might not mean low soil fertility, but the presence of many wild carrots alongside other plants that typically enjoy a low fertility environment, such as oxeye daisies and poppies, could tell us something.

You will need to observe the whole area, not just one patch of soil, to get a true idea of the soil type.

You should also note the conditions of the plants. For example, if legumes are present and look healthy while other plants are struggling, this could indicate low nitrogen levels in the soil (which can affect plant growth), legumes can harvest nitrogen from the air, so would be unaffected.

You'll get better at reading the land in this way as your experience grows. And while it's not an exact science, it will help give you a broad understanding of a site. Listed below are some indicator plants to look out for. This is not an exhaustive list, and the presence of one plant does not necessarily mean just one thing. But these indicator plants will help you to begin to understand the conditions of the land around you.

Alkaline/Limey Soil

• Red fescue
• Kidney vetch
• Plantain
• Blue sedge

Acidic Soil Indicator Plants

• Gorse
• Braken
• Heather

Clay Soil Indicator Plants

• Plantains
• Coltsfoot
• Docks
• Nettles

Sandy Soil

• Wild carrot
• Yarrow
• Poppies
• Wild marjoram

Wet Soil Indicator Plants

• Moss
• Rushes
• Himalayan balsam
• Creeping buttercup

Low Fertility

• Wild carrot and parsnip
• Oxeye daisy
• Poppies
• Common mullein

High Fertility

• Nettles
• Chickweed
• Chickory
• Common groundsel

Compact Soil

• Pineapple weed
• Couch grass
• Cleavers