Fumigation is a commonly used management tool, especially on soils used for potato production. Fumigation affects the nitrogen cycle by inhibiting nitrification and does so in two ways. First, it can kill soil organisms, including nitrifying bacteria. However, not all fumigants kill nitrosomonas. Specifically, metam sodium has been shown to not cause a decline in nitrosomonas populations (Li et al., 2017) while dazomet has been shown to cause such a decline (Fang et al., 2018). Little is known about the impact of fumigation on selectively killing nitrobacter. The second way fumigants affect nitrification is through enzyme degradation or suppression. As fumigants decompose, they form chemicals which temporarily inhibit the expression of the amoA enzyme and hence, delay the nitrification process (McCarty, 1999). Since nitrosomonas are not likely killed with metam sodium, this is the most likely cause of nitrification inhibition. However, it is not clear if the enzymes are inactivated in the soil or if the production of the enzyme by nitrosomonas is inhibited.

Check out the July 2020 issue of the Badger Common’Tater (https://issuu.com/bctater/docs/0720_standard) for the full article (pages 33-36), written by Ashmita Rawal.