Extension Logo
Extension Logo
University of Minnesota Extension
extension.umn.edu

Understanding nitrogen in soils

What you should know

  • Numerous nitrogen (N) sources exist. Consider these when evaluating the N budget.
  • Soil type and climate greatly affect nitrogen loss from the soil system.
  • Because Minnesota has such diverse soils and climate, N cycle interpretations should be site-specific.

Here, we’ll cover how nitrogen behaves in Minnesota soil systems and how to manage it for more profitable and environmentally friendly crop production.

Basics of nitrogen

 | 

Inputs of N for plant growth

 | 

Nitrogen transformations

Nitrogen, present or added to the soil, is subject to several changes, or transformations. These dictate the availability of N to plants and influence the potential movement of NO3--N to water supplies.

 | 

Nitrogen loss from the soil system

When developing N programs and evaluating environmental effects, consider nitrogen’s mobility factor in the soil. Sandy soils may lose N through leaching, while heavy, poorly drained soils may lose N through denitrification.

 | 

Key points for crop producers

Considering the many transformations and reactions of N in soils, there are some major points to keep in mind:

  • Although you can add either organic or inorganic N forms to soil, plants only take up inorganic N (that is, NO3--N and NH4+-N).
  • One form isn’t more important than the other and all N sources can be converted to NO3--N. Commercial N fertilizers, legumes, manures and crop residues are all initial sources of NO3--N and NH4+-N.
  • Once it’s in the plant or water supply, it’s impossible to identify the initial source.
  • Nitrate is always present in the soil solution and will move with the soil water.
  • Inhibiting the conversion of NH4+-N to NO3--N can result in less N loss and more plant uptake. While it’s not possible to totally prevent the movement of some NO3--N to water supplies, sound management practices can keep losses within acceptable limits.

Fabian G. Fernandez, Extension nutrient management specialist and Daniel E. Kaiser, Extension nutrient management specialist

Reviewed in 2021

Page survey

© 2024 Regents of the University of Minnesota. All rights reserved. The University of Minnesota is an equal opportunity educator and employer.