Priming or a "Priming Effect" is said to occur when something that is added to soil or compost affects the rate of decomposition occurring on the soil organic matter (SOM), either positively or negatively. Organic matter is made up mostly of carbon and nitrogen, so adding a substrate containing certain ratios of these nutrients to soil may affect the microbes that are mineralizing SOM. Fertilizers, plant litter, detritus, and carbohydrate exudates from living roots, can potentially positively or negatively prime SOM decomposition.
- Bird, Jeffrey A.; Herman, Donald J.; Firestone, Mary K. (April 2011). "Rhizosphere priming of soil organic matter by bacterial groups in a grassland soil". Soil Biology and Biochemistry. Elsevier BV. 43 (4): 718–725. doi:10.1016/j.soilbio.2010.08.010. ISSN 0038-0717.
Plants often impact the rate of native soil organic matter turnover through root interactions with soil organisms
- Jackson, Oyindamola; Quilliam, Richard S.; Stott, Andy; Grant, Helen; Subke, Jens-Arne (July 2019). "Rhizosphere carbon supply accelerates soil organic matter decomposition in the presence of fresh organic substrates". Plant and Soil. 440 (1–2): 473–490. doi:10.1016/S0038-0717(03)00123-8.
(positive priming is the) acceleration of SOM decomposition caused by change in microbial community structure and extracellular enzyme production (Blagodatskaya and Kuzyakov 2008).
- Huo, Changfu; Luo, Yiqi; Cheng, Weixin (April 2017). "Rhizosphere priming effect: A meta-analysis". Soil Biology and Biochemistry. Elsevier BV. 111: 78–84. doi:10.1016/j.soilbio.2017.04.003. ISSN 0038-0717.
Rhizosphere priming is crucial for regulating soil carbon and nitrogen biogeochemical cycles. ... The presence of live roots can suppress soil organic matter (SOM) decomposition rates by 50% or stimulate it by 380%, when compared with soil incubations without plants (Cheng et al., 2014). ... The RPE is a change of SOM decomposition rate due to the presence of living roots and aboveground vegetation (Kuzyakov, 2002), while the general priming effect (PE) is a change of SOM decomposition rate due to substrate additions Löhnis, 1926; Bingemann et al., 1953).