Tillage Technology

Today, more than six billion people in the world rely on food grown on just 11 percent of the global land surface. That’s the amount of land that is considered arable, or able to produce crops at all. Even less land – only 3 percent of the Earth’s surface – offers inherently fertile soil. The rest is considered marginal farmland. Some of the most fertile land is in the Midwest of North America, central Mexico, Argentina, Britain, northeastern China and a few pockets in other parts of the globe.

Understandably, when fertile soil is used, when crops are grown on them, the fertility is drawn out. Nutrient levels diminish as plants draw them out. Moisture levels decline. Repeated plowing and cultivating can open it up to erosion from wind and water. In the last quarter of the 20th century, agricultural researchers found new ways to preserve soil fertility by managing the residue left on the field year to year through a variety of reduced tillage or conservation tillage techniques.


Crop Residue Management and Tillage System Definitions
Crop Residue Management (CRM)
Intensive- or
Conservation Tillage
Moldboard plow or other intensive tillage used No use of moldboard plow and intensity of tillage reduced Full-width tillage, but further decrease in tillage intensity Only the tops of ridges are tilled No tillage performed since harvest of previous crop
< 15% residue cover remaining 15-30% residue cover remaining
30% or greater residue cover remaining on soil surface after planting

There are a variety of tillage methods available to farmers today. As the table above indicates, farmers using conventional tillage practices will work the ground intensively several times during the growing season. After the harvest is over, conventional farmers will use a moldboard plow to turn most of the residue of last year’s crop back underground, leaving the soil surface exposed over the winter. The farmer may go over the field again before planting and again to mechanically cultivate weeds between row crops several times before harvest.

The different forms of Crop Residue Management (CRM) practices start from an understanding that leaving stalks or straw on the field will protect it from wind and water.

Farmers using reduced tillage practices still go over the whole field with a cultivator after harvest, but they will leave between 15 and 30 percent of the residue on the field.

Mulch till systems simply leave more residue than reduced tillage, usually around 30 percent.

Ridge till systems will leave the residue from harvest undisturbed before planting, except if the farmer needs to inject nutrients. Planting is completed in a seedbed prepared on four- to six-inch high ridges that are formed and rebuilt during row cultivation for weed control. Residue is left on the surface between ridges.

No till systems leave the residue undisturbed from harvest to planting except for fertilizer application. In no-till systems up to 70 percent of the field will be covered with crop residue from last year. Weeds are controlled through pesticide applications.

Statistics from a national survey by the Conservation Technology Information Center show that conservation tillage practices are increasing.

  • 40.7 percent of farmers in 2004 were using some form of conservation tillage (either mulch-, ridge-, or no-till). That’s up from 26.1 percent in 1990.
  • Another 21.5 percent of farmers in 2004 were using reduced-till systems. That’s down slightly from 25.3 percent in 1990.
  • Only 37.7 percent of farmers in 2004 were still using conventional tillage techniques, down from 48.7 percent in 1990.

If we add the figures for reduced- and conservation-tillage practices, fully 62.2 percent of farmers are leaving some residue on their fields. Most of the growth in conservation tillage since 1990 has come from expanded adoption of no-till practices. U.S. cropland planted with no-till more than tripled from 17 million acres (6 percent of total cropland) up to 62 million acres (22 percent) between 1990 and 2004.

film_kaliff_RMark Kaliff (left) is part of one of the largest farming operations in central Nebraska and uses ridge-till systems. “It starts at the harvest time, and we try to really get the corn head to do the best job that it can of chewing up those stalks,” Mark says. “And then we come back and we follow those same ridges that allows that tractor to follow that same path to fertilize. So, we’re just fertilizing just the area that the corn plant is going to use. And then we come back and follow that with the planter and trying to stay on those same exact rows each time. It cuts down on compaction.”
Chris Ziegler grew up learning farming from his grandfather Clyde Ehlers, and he’s seen the changes in tillage
. “He was a tillage-oriented person,” Chris remembers. “You disc in the fall. You disc in the spring. You fertilizer. You field collate. You plant. Then you cultivate. Then you hill. We went to ridge-till when fuel prices started climbing.”

film_lee_RAgronomy professor Don Lee says that the development of GMO Roundup Ready crops have made conservation tillage more feasible by reducing weed pressures. “The farmer could apply this herbicide (Roundup) even when the crop plant was up and growing and kill any weeds that were emerging,” Don says. “As a consequence, minimum tillage farming in states like Nebraska has increased.”

For all of these farmers, changing their tillage system changes all of their other systems as well. Conservation tillage affects machinery, chemical, fuel and labor costs. In general, long-term field trials on a variety of fields show slightly higher yields with no-till systems than intensive tillage, and even higher when no-till is combined with crop rotation systems. Conservation tillage farmers report slightly higher profits, as well.

But the main reason that farmers seem to choose conservation tillage practices involve maintaining a better environment – conservation tillage reduces soil erosion, produces cleaner water runoff, increases water infiltration from the surface to subsoil layers, improves soil moisture, and improves the quality of the soil over the long term.

Written by Bill Ganzel, the Ganzel Group. First published in 2009. A partial bibliography of sources is here.

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