I believe the atmospheric air we breathe is about 70% or more nitrogen. So there is no shortage of nitrogen for microbes etc to use in breaking down any sort of residue.

Through the centuries the soils of the midwest and elsewhere were made by piling residue on top of residue each time the earth made a trip around the sun. Over the summer temperatures warmed, and residue broke down, slowly.

The natural by product of residue breaking down with nitrogen is a release of CO2 gas. Now CO2 is being a hot topic these days as a cause of global warming....(please don't get off track on that!)

However CO2, released when there is a plant leaf canopy above to use it, is a very important positive force for life on earth as the CO2 provides the needed fuel for plants to use along with sunlight, in photosynthesis. The green heart of growing things.

The problem occurs when we in our impatience insist that residue break down quickly, maybe by applying additional external N, or by plowing residue in various ways.

The microbes suddenly go to work and release CO2 at a time when there is no leaf canopy above to use it in photosynthesis.

By leaving residue on the surface between the till strips and rows of growing crop, we allow the microbes to use mostly atmospheric N to slowly break down residue and release CO2 at a time when there is a canopy above to use it.

According to the USDA soils lab in Ames, release of CO2 is why a crop often greens up visibly after cultivating.  It's NOT anything to do with cultivating and roots, it's just cultivating breaks up the surface crust annd allows a quick release of CO2 from the soil which increases photosynthesis in the leaves above and causes the plants to appear greener.

Here is a midsummer customer's photo from E C IA a couple years ago showing residue in later stages of breakdown and the resulting very green leaf canopy above.

Now that we are developing the tools to handle the immense amounts of residue produced by a 200 bu+ corn crop I do not feel that there is any reason to artificially try to change the normal cycle of residue breakdown.

Leaving residue on the surface also leaves it where the earthworm likes to get his food - on the surface. Earthworms help breakdown residue and convert some of it while aerating the soil deeper than we would usually be able to work the ground. IF residue is left consistently on the surface the earthworm population can come up next year and find food. If we leave it on the surface one year and bury it the next it is logically hard to build the worm population beyond some base level.

Here's the photo mentioned:

Jim at Dawn

(Dawn Striptill Corn on Corn E IA 7-25-05 Cust photo -last yr residue + spring cleared stripHP_0175A_1.jpg)

Dawn Striptill Corn on Corn E IA 7-25-05 Cust photo -last yr residue + spring cleared stripHP_0175A_1.jpg (46KB - 90 downloads)