North Central Ohio, across the Corn belt ! | quote, Ministry of Agriculture
The Nitrogen Cycle
( The nitrogen cycle is a good example of the far-reaching effects of soil life. The cycle begins when bacteria in the root nodules of leguminous plants like alfalfa and soybean convert nitrogen gas from the air to ammonium or nitrate ions in the nodules.
Different microbes then break down the nitrogen-rich plant tissue to release ammonium into the soil. This step in the cycle is called mineralization. Next, yet another set of soil microorganisms convert ammonium to nitrate, the nitrogen source most readily taken up by plants.
Some of this ammonium and nitrate, however, is absorbed by other soil organisms as part of their bodies. This makes the nitrogen temporarily unavailable to plants. In effect, it's stored for later use. As the organisms die, their nitrogen is released for uptake by other organisms or plants.
The final step in the cycle is denitrification, in which still one more group of bacteria convert nitrate to nitrogen gas, releasing it back into the air. This process takes place mostly under water-logged conditions.
Soil bacteria need nitrogen to decompose plant residues, mostly made of carbon compounds, to release ammonium (mineralization). If residue contains insufficient nitrogen relative to the amount of carbon, the bacteria tie up (immobilize) soil nitrogen reserves, including what was applied as fertilizer.
At a carbon:nitrogen ratio below 25:1, mineralization occurs. At ratios above 25:1, you get immobilization. Alfalfa hay at 13:1, for example, allows mineralization to proceed. But corn stalks (60:1) and sawdust (400:1) result in immobilization of nitrogen - it's present in the soil but temporarily unavailable to a crop. ) End quote |
Effects of an early manure application and microbes
