As seen in Illinois AgriNews - http://www.agrinews-pubs.com/Content/News/Rural-Voices/Article/Consider-residue-breakdown-and-mineralization-/8/15/15132
To optimize corn production, producers should today pay close attention to carbon-to-nitrogen ratio and mineralization, as they manage soil nutrients in the spring and fall. The fall harvest date and the spring’s temperature and moisture levels have a significant impact on the breakdown of crop residue and mineralization, the release of nutrients into the soil.
Breakdown of Crop Residue
We know that the higher the carbon–nitrogen ratio is, the longer it takes plants to break down. For example, because of their high carbon–nitrogen ratio of 60 pounds of carbon (C) to 1 pound of nitrogen (N), cornstalks break down over a longer time than alfalfa or tillage radish because their C:N ratio is about 17:1 and 19:1 respectively.
If we look at three different corn harvest dates—September 1, October 1, and November 1—we’ll discover a significant difference in how well postharvest crop residue breaks down. Given adequate moisture and temperature, we will witness more breakdown in corn residue when it is harvested early in September. Even though corn residue has a high carbon–nitrogen ratio, it will break down, give nutrients back to the soil and be more available.
On the other hand, corn harvested in November has a very small window for the breakdown process.
In our Midwestern soils, mineralization takes place naturally in the fall and spring. Soil organisms decay cornstalks, for instance. We know that this decomposing influences how fertile the soil is and how well the next crop grows. Yet, soil scientists are still studying the how and why of mineralization. Much is unknown, so we cannot fully predict the effect mineralization has on soil.
What we do know is that mineralization requires proper moisture with adequate temperatures. In other words, if the season is too cool—below 50 degrees F—we do not have much biological activity. Therefore, we have very minimal to no mineralization. Once temperatures rise above 50 degrees F and the weather provides adequate moisture, the mineralization in our soils increase. As a result, the soils gain more organic nitrogen, which has a direct relationship in helping to break down plant residue.
Looking at the extended fall we just experienced in 2015, we had more mineralization and improved breakdown of plant residue. This current spring is our next opportunity to break down crop residue. The decomposing process during the springs of 2014 and 2015 was poor. We had cool springs with saturated soils, which resulted in delayed mineralization because corn residue with a high C:N ratio did not break down well ahead of planting spring crops.
A Variable 2016
This year we’re seeing the exact opposite. The Midwest had a very mild winter after a long extended fall with a fairly early harvest. In both seasons, the breakdown of high carbon-to-nitrogen crops went well.
The spring of 2016 has arrived early and has provided some variability. In many cases, it’s a mixed bag in the Midwest, with both wet and dry soils depending on your area. Even in those areas that have had adequate moisture, we’re certainly seeing the start of mineralization two to four weeks earlier than normal, which will provide a flush of nutrients for our 2016 cash crops.
Likewise, in the areas that have warm and dry temperatures with not much moisture, we are going to see minimal mineralization, which may not adequately break down crop residues, resulting in fewer nutrients available in the spring.
When we begin to monitor our plan to ensure adequate nutrients for maximum production of our cash crops, we must consider the fall’s harvest date and the spring’s temperature and moisture levels, along with efficient crop-residue decay, our crop’s C:N ratio and mineralization success.