by Dr. Calvin Trostle, Extension Agronomy, TAMU Soil & Crop Sciences, Lubbock, (806) 723-8432, ctrostle@ag.tamu.edu

This week I was in Mitchell County, Texas to talk about cover cropping (see companion article in this month’s RCNL).  As cover cropping has become a national topic of interest in agriculture, sometimes I think the interest and enthusiasm gets carried away with some statements about soil and our farming practices that need some perspective.

This could very well be purely unintentional.  But if a Texas farmer is lectured about any of the comments below, especially in drier regions of the state, he or she may not know what to believe.  An Olton, TX farmer approached me earlier this year about some of the comments below, and wondered if they “were doing it all wrong’ in their farming operations.  I assured them they were probably doing just fine, but let’s review and see what we can learn.

So here are five statements I hear about agricultural practices—including (my opinion) attempts by those from regions with more rainfall that try to impose suggested practices on producers in drier regions.  I believe these statements can be confusing, even misleading.

1. “Fallow periods kill the soil…” No, they don’t.  Soil is a fantastic medium with all kinds of different microorganisms as well as worms, nematodes, and other biota.  This statement probably implies bare soil or some residues, but soil biological activity continues—albeit at a lower level.  Increased soil biological activity can lead to better nutrient cycling and possibly increases in stable long-term organic matter.  Why is fallow a common farming practice in many regions of the western Great Plains and other regions?  Because is saves and stores soil moisture for the next crop!  Elevated soil biological activity will resume once cropping occurs.
2. “Farmers have destroyed their soils…”  This statement is most likely targeted at western dryland regions of Texas.  Some believe that tillage is the only way to manage wind erosion (listing soils, pulling up cloddy material, etc.).  Farmers doing conventional tillage for 50 years have not destroyed their soils (if they did, it most likely comes from excessive rain run-off and subsequent loss of surface soil).  Farmers may farm a degraded soil resource, but like #1 above, let’s give soil some credit!  This unique medium can resume an elevated level of biological activity quickly.  When you produce 3 bales of cotton with moderate irrigation, or 4,000 lbs. of grain sorghum on dryland in a dry region, or 45 bu/A dryland wheat in the High Plains (and many have), you do not farm destroyed soil.  Perhaps degraded, but not destroyed.
3. “We need fungal dominant soils…” The bulk of soil biological activity from microorganisms is bacterial and fungal.  Numerically, bacteria far out-number fungi.  But both have significant roles in biological and chemical processes in soils, and they are complementary to each other.  Each type of organism (bacteria, fungus) has different contributions to nutrient cycling, conversion of organic matter to humus, etc.  But university soil microbiologists I know do not support this statement.  If you have different types of decaying residues in soils then soil fungi may increase relative to bacteria.  But regardless of what level each is, they work together to make soil a dynamic system.
4. “Cover crops don’t use water…” I don’t think technically this is what is meant, rather the net effect of cover cropping is a neutral water balance or even positive if cover crops are used.  But what is meant is not what is said:  cover crops use water.  You know you cannot get something from nothing.  You have known that a long time.  You can’t get a nice blanket of biomass and subsequent residues without using water.  Cover residues might conserve soil moisture by reducing evaporation from the soil surface.  But growth uses water.  Water use is measurable.  The question is, can over crops effect enough of a change so that rain fall infiltration, reduced evaporation, etc. lead to a favorable net balance (increase) in soil moisture for your agronomic crop?  Much more data is needed in this area.
5. “Tillage kills VAM…” Vesicular Arbuscular Mycorrhizae.  These organisms are like a network of fungi that have a specific structure—hyphae—that can penetrate plant cells in one direction and extend through soil in the other direction.  These often facilitate nutrient acquisition and exchange with the roots.  Tillage will disrupt this association to some extent, but not to the point of killing all these microorganisms.  Which can quickly grow back.  The VAM in the words of one colleague are somewhat like starfish—one can become several if injured, torn up, etc.

You may have heard some of your own sharp statements about our soils and farming practices.  These are a few; if you have experienced others, I would like to hear about them.

Be sensible in your thinking about what you hear.  Texas A&M AgriLife staff are here to help you think through your farming operation and some of the things you can do to improve.  We are all seeking to optimize ways to farm better and take care of our soils.  But these statements above seem as if they might be intended to beat us down.  I am not buying it.  We are all conservation stewards to some degree.  Let’s look at the positives of what we can do to farm better, farm longer, and farm profitably.  Texas A&M AgriLife welcomes your thoughts and we are eager to partner with those exploring means to improve agriculture on your farm and for Texas.

Calvin Trostle
Professor and Extension Specialist
Lubbock, TX
803.746.6101
ctrostle@ag.tamu.edu