Jim Bauder’s Ag Notes:

FAQs About Tillage

By Linzy Browning

We have recently received a variety of questions related to tillage, so following are a few answers to producer questions about this topic.

What is the effect of tillage on soil microorganisms?

Although minute in stature, soil microorganisms have important ecological jobs.

Their most visible job is the recycling of organic matter. A healthy population of microorganisms will quickly break down plant and animal residue, leaving behind nutrients for the next generation of plants. Although less visible, the job of maintaining soil structure is no less important.

Many microorganisms are made of thread-like hyphae that help hold soil particles together, and others exude sticky substances that serve the same purpose. Microorganisms also protect groundwater by breaking down agricultural chemicals into less toxic forms.

Knowing the important roles of microorganisms, farmers must learn ways to protect them from degradation. Many producers have turned to reduced or no-till operations with varied crop rotations to increase the sustainability of their operations. Not surprisingly, these practices are very microorganism-friendly. A 1995-97 study in Alberta looked at soil microbial populations under wheat crops preceded in rotation by one of the following: field peas, red clover, fallow, or continuously cropped wheat. The study also compared the effects of conventional tillage and no-till practices on microorganism populations.

The final result of the study was that no-till fields had greater numbers of microorganisms compared to their conventionally tilled counterparts. Fallowed fields had the smallest populations of microbes. The fields that were preceded by legumes had the greatest diversity in their microorganism populations. In general, soil microorganisms respond well to reduced till and no-till practices, as well as varied crop rotations that include legumes.

How much moisture is lost to evaporation following the various tillage practices?
Evaporation loss is dependent on a variety of weather factors, including temperature, wind velocity, and humidity. Although these factors play important roles in evaporation, the most important and controllable factor is the amount of residue left on the soil. Residue cools the soil surface, decreases wind velocities near the soil surface, slows and traps rain and snow, and physically blocks water from leaving the soil.

The generally accepted values for evaporation losses due to tillage range from .25” to .5” per pass. Although the quantity of water loss varies with soil type, weather conditions, and implement type, some general guidelines apply to most situations.

Eliminate unnecessary tillage, and if multiple tillage operations are necessary, perform them as close together as possible. Connect tillage equipment to perform multiple functions per pass, and quickly close cracks made by chiseling or deep ripping.

The following table gives values for the amount of evaporation loss associated with various types of tillage. It clearly shows that the tillage methods that create the least disturbance conserve the most water.

Tillage Type	Water Losses After 1 Day	Water Losses After 4 Days
One Way	.33”	.51”
Chisel	.29	.48
Sweep Plow	.09	.14
Rod Weeder	.04	.22

Some online sources for more on conservation tillage:

www.pulse.ab.ca/newsletter/97fall/zillion.html -- Zillions of Lives Underground

www.mandakzerotill.org/book11/dry.html -- Practical Pointers For Increasing Yields Under Dry Conditions

www.uidaho.edu/extension/drought/01TillagePractices%20.pdf -- Tillage Practices for Water Management

www.monsanto.com/monsanto/layout/products/conservationtill-age/fswater. asp -- Conservation Tillage Makes Better Use of Precious Water Resources

www.ext.colostate.edu/pubs/crops/00516.html -- Dryland Cropping Systems, Colorado State University Extension Service