Tillage Insights..Why Till?

Tillage Insights by: Jeff Hammer

Why Till?

This is the most difficult question to answer. Virtually every Agronomist you talk to will have a different opinion on this subject. A farmer in central Illinois is going to till for a different reason than we would. In our semi-arid dryland environment I would tend toward as little tillage as possible to preserve soil moisture and structure. Normally the earlier we can till the better it will be for the following crop.

Often, I see a grower tilling and try to figure out what is the purpose for that tillage pass? If you are considering tillage, then you need to answer this question concisely. Do I need to fix ditches? Do I need to get heavy amounts of residue spread more evenly? Am I trying to alleviate compaction? If you don’t have a concrete agronomic reason, then chances are you don’t need to be doing it.

Deep Ripping

In some instances, deep ripping may be necessary in high traffic areas from loading of trucks, or heavily compacted controlled traffic areas. Wet harvest conditions usually cause the necessity for deep ripping passes. I would tend to discourage growers from ripping whole fields on our higher clay containing soil types. There have been some instances where ripping sands can show yield increases because sands tend to compact closer to the soil surface. In clay soils, capillary movement of soil moisture is much higher than sands. Therefore, the depths that

the profile dries out become much greater. Drying out an extra foot of soil moisture can create as much as 2” of moisture loss in clay soils. That may be the difference between making it through at hot, dry stretch at a critical growth stage or not. There are some instances where subsurface tillage can be effective, but I believe it needs to be isolated areas in a field.

Mulchmaster/All-in one tillage equipment

I won’t spend a lot of time in this area as there are a lot of new tillage options coming into this market. Most of them are centered around single pass all-in-one type of systems with residue management as the primary focus. Often you will see a residue minimizing section similar to a vertical tillage pass, followed by a deeper operation to minimize surface compaction. Then they have a harrow or rolling basket to finish the soil surface smooth for planting. While the market and technology has expanded greatly in this realm, they tend to be more popular in corn on corn growing regions of the US. This is for good reason as crop rotation normally provides ample time for surface residue to decompose and corn bean rotations leave differing amounts of surface residue to increase decomposition time for corn residue breakdown.

Vertical Tillage/Disc

The most popular type of tillage in our geography is vertical tillage. This tends to be minimally aggressive and the principle is primarily for residue management. Vertical tillage lifts soil vertically with less horizontal sheer and is designed to operate most efficiently at higher speeds. The primary benefit is less shearing of soil colloids maintaining better soil structure. Vertical tillage is also used pre-plant as a weeding option. You can get effective weed control with vertical tillage but weed size needs to be minimal and soil conditions dry. In wet soils we tend to get less lift and horizontal movement leaving weeds with roots attached. Vertical tillage is often used to smooth surfaces and fill smaller ditches. The inability to move large volumes of soil makes it difficult to fill large ditches with Vertical tillage. A typical disc will move much more soil and weed more effectively due to more aggressive angle of the discs. The biggest drawback to your basic disc is often soil moisture is too great and smearing of soil particles occurs, initiating compacted plow pans over time. However, filling of large erosion areas will be more quickly accomplished with a disc than vertical tillage. An interesting advancement in this area is now we see tools that can vary the amount of horizontal throw so the same tool can perform both operations.

In Summary

As you have probably concluded from this content I am not the biggest fan of
tillage in our arid environment. The primary reasons tillage has been
practiced over time is for weeding and seed bed preparation. Technology
advances in planting equipment have enhanced our ability to plant in high
residue. Research and most notably yield, has concluded that soil left
undisturbed becomes healthier over time and more productive. The decay of
old roots left undisturbed creates natural pathways for water and air
infiltration. Residue left on the surface reduces moisture loss leaving more
crop available moisture. The biggest realm still not fully understood is the
biological environment that is enhanced in undisturbed soil. Microbes and beneficial fungi populations become greater in number and help fix nutrients making some more available for crop use minimizing the impacts of environmental swings that can inhibit nutrient uptake. There are times for tillage. Fixing erosion and ditches is a must in no-till and any time we can get that work done earlier in the winter and allow mother more time to heal the damage we have caused, the better it will be for our soil.