Where improved soil quality is concerned, not all organic matter is equal.
The UN has designated 2015 as the International Year of Soils, "to raise awareness of the importance of sustainable soil management", which is vital for food, fuel and fibre production as well as ecosystem function and adaptation to climate change. Results from SRAP's DC-Agri field experiments have a key role to play in this.
The experiments, comparing the ability of a range of organic materials to build soil organic matter levels over time, have shown that not all organic matter is equal and that compost builds levels much more quickly than other organic materials. They also show that repeated applications of compost are a valuable means by which farmers can improve soil quality.
Soil organic matter (SOM) is the organic component of soil, consisting of three primary parts: fresh plant residues and small living soil organisms, decomposing (active) organic matter (OM), and stable OM (humus). OM is important to soil fertility and crop productivity, and building and maintaining it is vital for sustainable soil management. The amount of OM in soils depends on soil texture, climate, the inputs and composition of orgnaic materials, the rate at which orgnaic matter is decomposed and the type of farming system employed.
Arable soils contain typically 1-3% OM (generally higher in Scottish soils) whilst grassland soils usually contain more. In general, for any one cropping system, the natural level of SOM in a clay soil will be higher than that in a sandy soil and this level will be higher under permanent grassland when compared with a continuous arable rotation.
WRAP's DC - Agri field experiments have assessed the effects of different types of organic material additions over time to a network of seven experimental sites across the UK. The sites were selected to represent a range of soil types, climatic conditions and crop rotations.
To read the next bulletin with further details of the experiments and what they found, click here.