39 Follow us on @PrairieFarming Better Farming | January 2025 the microbes has a lower C:N ratio and contains more nitrogen than they need. In return, the microbes deposit this excess nitrogen into the soil, which is available for plants. This results in a nitrogen credit for farmers and creates a cost saving by lowering the nitrogen fertilizer required for the following cash crop. Management strategies How a farm handles nitrogen immobilization will depend on its rotation, goals, and other practices. Nitrogen immobilization is more of a concern before nitrogen-hungry crops like corn, wheat and canola. Growers can avoid high C:N ratio volunteer crops by terminating earlier during the vegetative stage to lessen the amount of nitrogen immobilized or decide to take on the added cost of additional nitrogen inputs. That extra cost may be worth it for growers trying to enhance certain benefits of high C:N volunteers. Another option is to plan on adding extra nitrogen fertilizer the next year to offset the tie-up when the volunteers are tilled in as green manure, for example. While there are benefits to allowing volunteer growth to occur to help with soil erosion and manage excess moisture, and build soil organic matter, the bottom line is this: It’s better to terminate the volunteer growth early when more N is available and the C:N ratio is lower. This allows soil microbes a better opportunity to break down residue so that nutrients are available for the following crop. BF JASON VOOGT Jason (P.Ag CCA) is president, co-owner and agronomist at Field 2 Field Agronomy in Manitoba. He has 30 years experience working for ag retail and industry. Jason Voogt photo Two types of fall management of volunteer growth: The two photos on the left show early termination with glyphosate, and the two on the right show seven-leaf heavy oat volunteers that were tilled with a high-speed disc. Agronomy Insider
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