What is YOUR goal when making a tillage pass?
Often, we farmers try to get in a routine when it comes to field work. We try to use the same tool for every spring tillage pass, we write detailed notes about down pressure settings and use phrases like “It worked last year why not again this year”, or my favorite “This is how my father, and his father, did it”. Unfortunately, these routines occur in fall tillage far too often.
When deciding what depth, or which tool, to follow the combine it requires a simple question. What goal am I trying to accomplish? Is it compaction, residue utilization, fertilizer incorporation, seedbed preparation, etc.? Once the overall goal(s) have been established, the right tool for the job can be used. Example: If my goals are to secure residue, and incorporate fall applied fertilizer, a Horsch Joker at a 3” depth would be perfect.
One of the most misunderstood reasons for a fall tillage pass is to “fix” the issues from the past season. These issues are most known as compaction and wheel ruts. Every pass made through a field causes some sort of compaction. In some soil types, and regions, heavy rain can cause surface compaction. That fact is, it’s inevitable with the physical contact being made. There are ways to lessen the impact, and with this link below, you can find out more.
Knowing what depth to set a tillage tool is simple when a goal is in place. The first step to setting a shank type tillage tool is using a “T probe” or penetrometer as shown below.
I use this device to find compaction layers, or zones. As the probe travels deeper in the soil, it is ordinary for the PSI (pounds per square inch) to increase as pore space decreases. It is important to take note of when the dial stays elevated, and at what depth. When the dial reaches 100-120 PSI, with a ¾” tip, the negative impact has begun. It is not until 200 PSI that the soil needs to be amended. At 300 PSI little root development is occurring.
The best way to amend compacted soils is with the right cover crop given the appropriate amount of time to develop deep root systems. The second best is using the correct tool to, not correct, but lessen the negative side effects. What will happen if used too frequently is poor soil structures causing even more compaction issues as pore space is decreased.
This is a common issue with fall tillage where the operator wants to bury the tool as deep as possible every year. What happens when it cannot be pulled any deeper? A plow pan is created, and a different tool must be used to achieve those depths. This is the reason for finding compaction layers, and then setting the tool accordingly. After the layer has been broken up, a proactive approach can be used the following season, so it does not persist.
The graph below shows the different PSIs at various depths in inches. As you can see, it would not be wise to set a tillage tool past the 10” depth since 9” is where the compaction layer is. The point being it is best to do only what is necessary. This will save on fuel, time and future problems that can be placed in a deeper profile.