Published on Tuesday, March 10, 2020
In corn-after-corn systems, the high amount of residue can immobilize nitrogen and make it unavailable to the following crop. Robust® and Res Plus are products the help to feed microorganisms in the soil. By supporting microbial communities, these products lead, in turn, to increased microbial degradation of corn residue in corn-after-corn systems. Applying these products in the fall may help speed up residue breakdown so the carbon penalty is paid off earlier in the growing season. This would allow for a transition from immobilization to mineralization of residue-bound nitrogen (N).
It takes about 30 lb. of N to break down every ton of dry corn residue matter. Each ton of dry matter already contains around 15 lb. of N, so it requires about an additional 15 lb. of N per ton to feed the microorganisms that break down the corn residue. However, the theory is that if we can supplement these organisms with nutritional stimulants, it may allow them to do more work in the fall and start mineralizing the N bound in the residue sooner the following year.
Timing and Amount of N per Application: As the organisms that break down corn residue become active in the spring, you want to have enough N available to feed them. Eight years of PFR data indicates that an additional 30 lb. N/A. is necessary in-season.
Fall Weather: If you have warm, moist conditions for an extended period of time after harvest, soils will begin the process of breaking down the residue sooner and continue it longer. If you live in southern Illinois, you have a better chance of increasing fall breakdown than if you live in central Minnesota. Perhaps the further north you live, these products may be of greater importance?
Tillage Timing: Populations of microorganisms that break down residue will build up as soon as soils warm up in the spring. Tilling, whether fall or spring, can result in warmer soils. By tiling earlier in the fall, you can begin to build up microorganism populations earlier and potentially reduce the N penalty in the spring.
For four years, we have tested products that claim to accelerate the decomposition of residue in the fall. These products contain either a bio-stimulant that accelerates residue breakdown or nutritional and activating agents that improve microbe health and residue breakdown. Keep in mind that the timing of the application and fall weather will play a huge role in breakdown, as well. These two products, Res Plus and Robust®, became PFR Proven™ products after providing a consistent yield increase and an average positive ROI over multiple years.
There are also equipment technologies that are working to address this issue by sizing and/or scoring the residue in order to create smaller pieces and/or more entry points for the microbes to enter the stalk and break it down. We have tested different heads and snapping rolls on combines to see what they may bring to the table. The chart to the left depicts our three-year, multi-location results for the Capello® Quasar Corn Head and the Yetter Stalk Devastator™.
Some hybrids produce much more residue due to their plant stature and structure. Keep that in mind as you plan your cropping systems as it may be a good idea to consider how you manage residue year-round, especially in a corn-after-corn rotation. For a complete list of products, including full ratings and available trait technologies, click here.
Author: Jim Schwartz
Categories: Agronomy, Agronomy Talk