Organic matter
As well as adding nutrients to the soil for your plants to take up, organic matter is also critical for a good soil structure – when broken down into ‘humus’ it helps stick the mineral particles together to form aggregates and keep the soil strong and stable.
Organic matter can be considered to be anything which is or was living. So it can include all the plant roots, worms, microbes and fungi living in the soil. While these play an important role (predominantly in breaking down bulky organic matter into aggregate supporting humus), it’s the remains of living matter which we’ll focus on here.
This type of organic matter is important to the soil because it helps to form soil aggregates, thereby improving soil structure, and it releases nutrients into the soil as it’s broken down into humus, which then helps to retain the nutrients within the soil.
Organic matter can take many different forms. In nature, organic matter in the soil includes dead plants, fallen leaves and decomposing animals. In gardening, organic matter is often ‘artificially’ added to the soil, for example as garden compost, farmyard manure, peat or leaf mould.