Nutrient availability from organic fertilisers depends on various factors. One of the key factors is carbon to nitrogen ratio (C:N).

Carbon-to-nitrogen ratio influences decomposition speed of organic matter. The ratio also determines whether nitrogen will be mineralized (released for plants to take it up) as the material is decomposed or if nitrogen will be immobilized (tied up) by the decomposer community as it breaks down the material.

The higher the C:N ratio the slower the mineralization

As seen in the visual below, a residue with a C:N of about 25:1 provides the perfect balance of energy and nutrients for soil microorganisms. Residues with a higher C:N, such as sawdust (about 400:1), wheat straw (80:1), or corn stover (60:1), will not provide enough nitrogen to support high microbial biomass and activity. In those cases, residues are slow to break down because microbes depend on any mineral (inorganic) nitrogen in the soil, out-competing plants for NH4₊ and NO3_–.

Residues with a C:N that is lower than 25:1, such as manure (20:1), alfalfa (12:1), organic solid fertilisers and microbial biomass (10:1) will supply plenty of nutrients to microbes thus that surplus nitrogen is released (or mineralized) into the soil. In these cases, the decomposers have all the nutrients that they require in the residues, so they remain active and decomposition occurs quickly.

For example, this is why corn residue breaks down more slowly than soybean residue. Corn has more total root and shoot residue than a soybean crop. In addition, corn residue has a higher C:N ratio, when compared with soybean residue, making it more resistant to decomposition than soybean residue.

Organically bound nitrogen: less leaching than mineral fertilisers

A key advantage of organic fertilisers is that the nitrogen they contain is less prone to leaching compared to the nitrogen in mineral fertilisers. This is because organically bound nitrogen is released gradually during the decomposition of organic matter, ensuring a longer-lasting availability for plants. In contrast, mineral fertilisers contain readily available nitrogen that leaches more quickly, especially during heavy rainfall or overwatering. This can lead to nitrogen loss and groundwater pollution.

Discover the difference with our products

At Den Ouden GrowSolutions, we understand the importance of the C:N ratio for efficient decomposition and rapid nutrient availability. That’s why we offer a range of products with a C:N ratio of 25 or lower, designed to accelerate the nutrient release process. Our products are ideal for fast-acting soil improvement, ensuring that your crops quickly benefit from the nutrients in the soil. This means you can optimize crop growth and yield by using these well-balanced fertilisers. Choose Den Ouden GrowSolutions and provide your soil with the nutrients it needs for optimal growth!

Information adapted from “Soil Organic Matter Does Matter”. Caley Gasch – Assistant Professor of Soil Health, North Dakota State University. Jodi DeJong-Hughes – Regional Educator in Soil and Water Quality, University of Minnesota Extension