Tillage Intensity, Corn Yields and Bottom Lines
by Greg Stewart, OMAFRA Corn Specialist

Someone once said there's nothing wrong with no-till corn that a little tillage won't fix. In the spirit of that statement, there are several tillage implements on the market today being promoted as providing just the right amount of tillage to boost no-till corn yields in line with conventional moldboard results. These systems virtually cover the tillage intensity spectrum from deep ripping to shallow harrowing...and most places in between.

The University of Guelph and Agriculture and Agri-Food Canada are assessing the potential for yield enhancement by increasing the intensity of tillage in the in-row zone, with funding support from CanAdapt and the Ontario Corn Producers Association.

Soil Loosening
One of the more obvious options for enhancing corn yields in reduced tillage systems is to do some extensive loosening, deeper into the soil profile. This can be done without disrupting much of the crop residue on the soil surface and can be confined to zones where next year's corn rows will be planted. This approach was implemented at the University of Guelph research sites near Granton, Ontario. Deep loosening was accomplished in the fall (prior to corn production) to a depth of 30 cm (12 inches) on some plots. Corn was planted the following spring over these loosened zones. A penetrometer, which measures soil resistance (via a steel probe), is used to measure soil strength during the corn growing season.

Figure 1 indicates that this deep loosening produced a soil profile with considerably less resistance than either the moldboard or no-till plots in the zone from 15-30 cm (6-12 inches) below the soil surface. You can also see where no-till shows increased soil resistance in the top 10-15 cm compared to moldboard tillage.

In general, the trends in soil resistance illustrated in Figure 1 were consistent across sites in 1998 and 1999 following previous crops of both soybeans and winter wheat (strawremoved).

Corn Yields
Table 1 outlines the corn yields from several tillage systems being compared at these sites both last year and this year. The first thing to notice is that loosening in the row zone (either 6 or 12 inches deep) appeared to have little impact on yields, even though the penetrometer numbers showed soil profiles that were significantly less resistant than in the no-till plots. A shallow fall discing generally produced yields that were in the same range as deeper in-row zone tillage. When comparing these results it's important to remember that both 1998 and 1999 were warmer and drier than normal during the early part of the growing season and planting conditions even in reduced tillage plots were not hampered by wet soils. Some of the most significant benefits to fall strip tillage may have less to do with soil loosening and more to do with creating an in-row area better suited for planting in seasons which are wetter or cooler than either 1998 or 1999.

The other interesting observation is how well reduced tillage performed on wheat stubble at these sites. Traditionally no-till corn after wheat has been considerably tougher to manage than no-till following soybeans. However it appears that increasing success rates following wheat relates more to moisture and temperature management than it does to soil density. For example, rotation benefits, tile drainage, straw removal, and perhaps some shallow tillage all may prove more important than extra tillage operations.

Bottom Line
No doubt some producers will look at Table 1 and say it proves moldboard plowing is still the way to grow corn. From a maximum yield perspective, that's hard to argue with. However, the point that most successful no-tillers have been making for some time is to not look solely at yields, but at bottom line profitability. I usually figure that it takes six bu/ac of corn to pay for the extra costs of moldboard plowing and spring cultivating compared to no-tilling and spraying a burn-down herbicide. So if you take six bushels off the moldboard yields, both following wheat and soybeans, the no-till option comes out looking pretty reasonable. And that's with no credit to the no-till system for prevention of soil erosion, building soil organic matter, or offering superior traffic-bearing capacity in the fall.

I realize commodity prices leave little room for mistakes in farming and that there are heavier soils, poorly drained soils, manure management concerns and other issues that may require some additional tillage intensity as part of the solution. The only reasonable course is to make decisions based on the best information at hand.

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