A Guide to Garden Soil
Soil, dirt, mud, whatever you call it is one of the most important parts of your garden but what is it and how do you care for it?
Soil is an amazing construct made up of many different materials including rock in varying particle sizes, minerals, organic matter, air, water and living organisms. A healthy soil has many types of organisms such as bacteria, fungi, yeast and earthworms all working to break down organic matter to turn it into nutrients which your plants will then take up.
Soil is the top layer of the Earth's crust formed over millions of years made up of rock particles, organic matter, air, and water.
Soil is made up of three layers.
Organic matter is made up from all living things. It includes dung and humas which is decayed organic matter such as leaf mould and other composted material as well as dead animal matter.
There are 5 different types of soil.
Loamy soil is the best type of soil, it looks how you would think soil should look. It feels smooth, not too dry or too sticky and when made into a ball will crumble easily.It is comprised of roughly 40% sand, 40% silt and 20% clay. This means it has a good well draining structure which still holds onto enough moisture for plants and has good levels of nutrients to help feed plants.
Sandy soils are rocky soils with a large particle size making it feel coarse and won't form a ball (unless damp). This means that water drains away very quickly and it doesn't hold nutrients. Sandy soils need lots of water and fertilizer to add nutrients for the plants. However it's not all bad news as sandy soils are ideal for planting seeds in and potting seedlings on.
Clay soils are rocky soils with a very small particle size making them feel smooth and when wet they are sticky and can easily be made into a ball. Clay soils are at least 25% clay and are lumpy and sticky when wet and hard like concrete when dry. The soil holds a lot of water which means you will have issues with drainage and it remains colder for longer delaying plant growth.
Silt soils are a mixture of sandy and clay particles giving it a silky smooth feel which cannot be made into a ball. Our best farmland is on silty soils because it is rich in nutrients and holds moisture very well however it is the least common soil and can become compacted very easily which makes it harder to work.
Chalky soils are full of lumps of chalk and stones and is made up of calcium carbonate which formed when the land was covered by ancient seas millions of years ago. Chalk is actually made up of the fossilized bodies of microscopic life from that time. Chalk downland is a thick layer of chalk covered by a thin layer of topsoil which make it difficult for most plants to grow.
Peat is a soil made up of water logged partially decaying organic material such as mosses, sedges, reeds and grasses that builds up in poorly draining wetlands over time. Peat bogs regrow at the rate of approximately 1mm per year and the industry is following government guidelines to reduce peat in the bags of compost you buy in the garden centre as well as provide peat free alternative based composts. Peat is used because it holds many times its own weight in moisture and also holds onto nutrients while also allowing for large pockets of air to be held.
Once you have identified the type of soil you have you can use a testing kit to determine the pH which is a scale showing weather a soil is acid, neutral or alkaline. This is important because some plants love acid soils and some hate acid soils which determines what plants you can have in your garden. If you wish to increase acidity you can dig in sulphate of iron and if you wish to increase the alkalinity of the soil and neutralize acidity you can add garden lime. Soils tend to become acidic over time due to fertilizers, rain, and the decomposition of organic matter, lawns in particular cannot take up nutrients when the soil becomes too acidic.
Improving your soil
It is easy to improve your soil no matter what type it is by adding organic matter. Country natural organic composted stable manure is an excellent source of organic matter which is ideal for digging into your beds and borders as well as around the base of established trees and large shrubs and bushes. It is very strong however and should be dug well in about a month before planting bedding or vegetable plants especially potatoes. It helps break up clay soils and also improves the retention of moisture and nutrients in sandy soils.
You can make your own composted organic matter (see our guide to composting) and you can also make your own leaf mould by filling bin bags with fallen leaves, make a few holes in the sides of the bag. When the bag is almost full sprinkle it with water, tie it up and stack in a shady spot. Most leaves will rot down and can be used in a year although some may take a little longer while conifer and evergreens can take 2 to 3 years to break down. Adding a compost accelerator such as Garotta can speed this up by up to 50%. You know when it's ready for use when it looks like a rich brown crumbly soil. If you have more space a leaf cage made of wire is a more effective way and can also provide an overwintering habitat for beneficial creatures in your garden.
Organic matter should be worked into the top 6 inches (15cm) of the soil and if applied as a top dressing should be no more than 2 to 3 inches (5 to 7.5cm)
What do you do however if you have a garden which is mainly rubble with a thin layer of topsoil? This is found mainly in the gardens of newly built houses and also in urban gardens. One option is to dig out all the rubble and build up the soil with large quantities of manure and topsoil. Whilst this is effective it can be costly and time consuming. Another option is to build raised beds which only need to be 12 inches deep (30cm) to support most plants. If you want larger trees and shrubs; large pots and planters would be a better option.
You can supplement the nutrients in your soil in several ways. Angus rockdust is a rich in minerals and can be dug in to all soils every year. Planters, hanging baskets and raised beds can be helped by adding slow release fertilisers which work for up to six months. General purpose fertilisers such as Vitax q4, Growmore, or Fish Blood and Bone can be added around the base of established plants or dug into the soil. Acid loving plants can be fed with Vitax conifer and shrub, whilst roses can be fed with Toprose. Adding Rootgrow Myoorhizal fungai to the root balls of any trees or shrubs when you plant them and add a small amount of Bonemeal in the bottom of the hole under a good layer of soil will also be highly beneficial.
Having a healthy soil will help to make your garden reach its full potential and remember if you have any questions our experts are here to help.
