According to a new study from the University of Illinois (USA) - "The short-term effect of nitrogen fertilizers on carbon mineralization in the decomposition of corn residues in the soil", excessive nitrogen introduction leads to a decrease in organic carbon.

It is reported by futurefarming.com.

Such results were obtained by the researchers of the University in the production crops of corn. To do this, the scientists tested the remains of corn grown with high doses of nitrogen fertilizers or without them. They found that the presence of nitrogen (exogenously applied to plant debris or incorporated into corn tissue) not only accelerates the decomposition of the residue, but also produces more carbon dioxide. At the same time, the form of nitrogen application (potassium nitrate or ammonium sulfate) did not matter.

“By intensive application of nitrogen fertilizers, you can get more corn biomass and yield, but this means that there will also be more plant residues in the soil. However, the resulting carbon cannot be stored in the soil. Nitrogen in the residue stimulates microorganisms that burn carbon through respiration. You can invest more, but you can't save,” says Richard Mulvaney, professor at the Department of Natural Resources and Environmental Sciences (NRES) at the University of Illinois.

At the same time, the specialist added that carbon in corn residues comes from the atmosphere and returns to the atmosphere during decomposition. But the problem is that when microorganisms have a high supply of nitrogen, their need for carbon as an energy source increases. Thus, at high levels of nitrogen in the soil, their demand may exceed even carbon stocks in the residues.

Thus, during the first month, the decomposition of carbon residues occurred more likely in the presence of nitrogen fertilizers than in their absence. However, it was noted that carbon dioxide production in the following month was slower for the fertilized soil than for the unfertilized soil. By the end of the study, the total amount of carbon dioxide produced was greater with the addition of nitrogen than without it.

These results explain why soil organic carbon cannot accumulate in high residue corn fields. The researchers suggest that farmers avoid over-fertilization of nitrogen.

SuperAgronom.com