Soil Food Web
Constituting the smallest fraction of soil yet playing the leading part is organic matter. As well as dead components such as straw stubble and previous crop roots, it consists of a combination of living organisms – including worms, mites, beetles and micro-organisms - which are essential when it comes to efficient food production. Not only do they help the decomposition of organic particles and turn them into nutrients, they keep soil in good shape, protect roots from soilborne diseases and regulate greenhouse gasses.
Often referred to as ‘the soil food web’, myriads of organisms in this closely knit community co-exist and rely on each other for food and energy:
- Bacteria decompose organic matter, mineralising the nutrients they contain and converting them into a form that can be instantly absorbed by plants. As well as enriching soil fertility, these useful members of soil biological community release hormones that stimulate plant growth and produce antibiotics to fight root diseases.
- Fungi also feed on surface litter and release enzymes which break them down into simpler forms. They also help to bind soil particles thus improving soil composition.
- Microbes including nitrogen-fixing bacteria and mycorrhizal fungi live in the rhizosphere – a zone of soil around that root of the plant – where they form mutually beneficial relationships. The roots release carbon which is used as food by the microbes and the plant is supplied with essential nutrients in return. Nitrogen-fixing bacteria deliver nitrate which can be readily absorbed by the roots whereas mycorrhizal fungi offer minerals such as phosphorus to the host plant. The symbiotic relationship makes the plants less prone to disease and drought stress and stimulates fine root growth, subsequently increasing nutrient uptake.
- Protozoa, a group of water-residing beneficial organisms which feed on bacteria and fungi, facilitate the ease of nutrient uptake to the plant thanks to their ability to convert nutrients into mineral forms that can be instantly utilised by plants.
Some conventional farming techniques, including ploughing, cause the reduction in beneficial microbes which in turn restricts plant access to natural nutrients and makes them more prone to soilborne diseases. Minimising soil disturbance, on the other hand, preserves its structure and protects the habitats of the valuable organisms living within. The benefits include higher levels of organic matter, better nutrient availability and a healthier crop with a better root system and increased disease resistance.