Soil Science Explained

Soil is a lot more complex than you might first think! It might just look like dirt in the garden, but where has it come from and how can it differ so much from place to place can tell an interesting story. Let's dive in to soil science!

The process of soil formation and development is known as Pedogenesis (already sounding more complex than you first thought?!) Put simply, soil is made up of organic matter, mineral material, water and air and soil development is influenced by the following factors:

• Parent Material – This refers to the rock that has been weathered down to form the soil. The rock type influences the chemistry and texture of the soil.
• Topography – This is the basically how the land lies. Soils formed on slopes tend to be better drained than soils on the bottom of a valley floor, and steep slopes can slow down soil development due to increased erosion transporting the sediment away. Topography also impacts microclimates, whether a slope is north or south facing can impact depth and texture of soil.
• Climate – Out of all the variables that come with climate, temperature and moisture have the most impact. These affect rates of weathering so amount of soil build up, and affect the moisture content of soil. Moisture can then affect the pH of soil and impacts the rate of decomposition of organic matter.
• Organisms – Soil nutrients are strongly affected by organisms and plants within the soil and they have a particular influence on nitrogen and carbon content. Surface vegetation can also help the build up of soil by protecting the soil beneath from erosion.
• Time – Soil formation is a long and ongoing process, time influences all of the processes above until eventually a soil reaches maturity and a steady equilibrium state.

With all of the above factors influencing soil formation, it is no surprise that soil types vary so much from place to place. Our farm in Lancashire is based on predominantly wet, sandy and loamy soils with a slightly acidic pH, but as soon as you move slightly more inland or further north or south, soil characteristics become completely different.

Soil Texture

Whether your soil is sandy or clayey, free draining or wet, acidic or alkaline, it will determine how well certain plants grow. The texture of soil can give you a good indication of soil type. Clay feels sticky and can be moulded in your hand, sandy soils feel gritty and silt soils feel quite smooth. You can find some good flow charts online to give you a good idea of soil type, just from the feel.

Soil pH

The pH of soil is also important in determining what will grow well in your garden. Unfortunately this isn’t quite as simple as just feeling the texture, it’s a bit more scientific than that! Most garden centres sell quite cheap pH testers though, so if you wanted to find out a bit more about your soil then they are probably worth giving a go.