Soil organic carbon (SOC) is the carbon stored within the soil and forms the basis of soil fertility. It is a part of soil organic matter that plays a key role in soil health through biological, physical and chemical functions. (Organic Carbon Stock)
Although different soils have different levels of SOC, surface layer has the highest level of SOC which decreases with depth down the soil profile.
Building Organic Carbon Stock Of Soils
Experts strongly recommend that the best way to build organic carbon stock of soils is by ley farming which is growing of grass or legumes in rotation with grain or tilled crops to improve soil structure and fertility, thus disrupting pest and disease life cycles.
This system enables recycling of residues, minimises erosion and ensures rapid build-up of organic soil carbon.
Secondly, applying manure and recycled organic materials to the soil is considered the practice with greatest potential to increase SOC.
Mature composted products are best used for building SOC because it provides high quality carbon nutrient.
Similarly, fertilisers are also used for improving SOC because it increases crops productivity which in turn optimises residue inputs to the soil.
The practice of irrigation also increases decomposition rates by facilitating rapid breakdown of organic matter in the soil to a more stable humus state, thus increasing plant productivity which in turn increase residue inputs that result in higher SOC.
A point of note to farmers however is that tillage, fallowing and erosion have negative consequences on the SOC levels of soils.