Mineralisation
Mineralisation is the process through which organic materials, such as crop residues, compost and manure, are transformed into inorganic nutrients. During this process, micro-organisms produce various enzymes that catalyse the breakdown of different organic matter structures. This process requires energy and therefore also results in the release of CO2 through microbial respiration. The BIOSIS platform for now focuses on the mineralisation of macronutrients including nitrogen, phosphorus, potassium, sulphur, calcium and magnesium. A large group of different bacteria and fungi are capable of carrying out this process.
Mineralisation is an important process to consider in the Nutrient cycling model as it is the step that converts aboveground organic inputs from plants and animals to nutrients that can be utilized by plants and cycle through the belowground food web. Mineralisation is coupled with the process of microbial respiration considered in the Carbon and climate regulation model. Organic matter consists of both nutrients and carbon. During mineralisation, microbes take up nutrients and carbon from organic matter resources but also release CO2.
There are many different methods to measure mineralisation. Microbial respiration is often measured as a proxy for estimating the capacity of a soil to recycle nutrients. Other methods tackle the mineralisation of specific nutrients such as nitrogen or phosphorus. These methods include soil incubations, enzyme analyses and functional genes associated with the cycling of different nutrients[1],[2],[3].
[1] Jarvis SC et al. 2001. An improved soil core incubation method for the field measurement of denitrification and net mineralization using acetylene inhibition. Nutrient Cycling in Agroecosystems 59: 219–225.
[2] Drinkwater LE et al. 1996. Potentially Mineralizable Nitrogen as an Indicator of Biologically Active Soil Nitrogen. Methods for Assessing Soil Quality 49: 217–229.
[3] Dick RP et al. 2018. Cross-laboratory comparison of fluorimetric microplate and colorimetric bench-scale soil enzyme assays. Soil Biology and Biochemistry 121: 240–248.