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Soil organic matter – why?
Dr. Victor Martin

As of Sept. 21 our area is essentially unchanged. Moderate to severe drought is creeping into the northwest corner of the state and along the border with Oklahoma. Fall crop harvest is underway and with forecasted conditions should proceed rapidly. The six to ten-day outlook (Sept. 28 to Oct. 2) indicates above normal temperatures (70 to 80% chance) and normal to slightly above normal precipitation (30 to 50% chance) which isn’t a great deal of rain. The eight to 14-day outlook (Sept. 30 to Oct. 6) indicates more of the same. Good news for getting fieldwork done and prepping for wheat planting. One side note that many producers are well aware of is much larger than normal numbers of armyworm. Today, let’s consider the value of increasing soil organic matter in our area, especially for sandier soils. Next week – How to increase it.

First, what are the types of organic? And we will skip the technical terms here.

• First, there is the recognizable “stuff” on the soil surface and in the soil that is recognizable for what it is – say wheat straw, corn stubble, or weeds.

• Second, there is material that is partially broken down and sort of recognizable but the bacteria, fungi, etc., have been working on it.

• Finally, there is the well-decomposed organic matter termed humus. This has been broken down to the point where it is totally unrecognizable and typically very dark brown or black. This like the material you can but in bags at a garden center or as composted material. What is left is resistant to breakdown by microbes but will still slowly break down over time. When agronomists and soil scientists discuss increasing organic matter, this is what the mean.

• And also here it should be noted that more than plant material but also animal waste (urine and manure), dead macro animals, and very importantly microorganisms.

Now what are the benefits of the various types of organic matter?

• Especially, the first two types, but really all three, are food for various microorganisms necessary for healthy soil and plant health.

• As they break down, eventually into humus, they will release plant nutrients such as nitrogen, potassium, sulfur, etc. as they break down the material. Even as humus, one percent organic matter can release 10 to 15 pounds of nitrogen per year.

• Organic matter (cover) on the soil surface decreases evaporation, moderates soil temperature, increases infiltration, helps suppress weeds, and protects the soil from wind and water erosion.

• There are two things in the soil that can hold water and nutrients. One is soil clay. The other is organic matter. In fact, organic matter can hold up to 300% its weight in water. Producers on sands can’t really increase their clay content but over time they can increase organic matter content.

• Finally, organic matter contributes to a lower soil bulk density which is better for plant root growth, and help provide stability for soil structure which aids in macro and micro pore develop.

Dr. Victor L. Martin is the agriculture instructor/coordinator for Barton Community College. He can be reached at 620-792-9207, ext. 207, or