Ag Instructor Vic Martin: Can We Improve Our Soils?

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Great Bend Tribune
Part I

Published August 4, 2019

Well, after a long period of time, part of Kansas is classified as abnormally dry.  It happens to be centered in our area with Barton and the surrounding counties.  This may change next week after some recent rains for part of the area but as this is written, Friday, the rains have been heavy but spotty.  There is a chance of rain this weekend and we are moving into a more unsettled period.  All our summer row crops definitely need the rain, corn, milo, and especially soybean fields where pods are starting to fill.  Last week’s column described what factors make a good agricultural soil.  How can move work towards the Goldilocks’ spot for soil physical and chemical conditions?  If a soil is less than idea, how can we improve them?

  • Our goal is to prevent wind and water erosion, maximize infiltration, optimize water holding capacity and aeration, and optimize the soil chemical environment. 
  • It isn’t practical to try and adjust soil texture, the relative proportions of sand, silt, and clay, on a large scale basis.  For small areas, lawns, plant beds, and other small landscape or production areas, it is practical, but not cheap to “create” an ideal soil for the use.  However, we can improve soil physical and chemical conditions in several ways.
  • Before we proceed to the next bullet point, soil pH is a key factor working towards improved conditions.  After appropriate testing, the pH is good, slightly acidic to slightly basic (6.2 – 7.2), basic (above 7.2), or acidic (below 6.2).  Increasing the soil pH when acidic is a matter of the proper soil test to determine the amount of liming needed.  There are a number of liming amendments from ag lime to burned lime.  Once raised, with proper management, acidic soils should maintain proper pH for a period of years depending on the cropping patterns and cultural practices.  For high pH soils on a field scale, there are amendments such as sulfuric acid and sulfate products to lower pH but they are normally cost prohibitive on a field scale.  Instead, it is better to manage the problem through crop selection and where pH is high and soluble salts are present, through amending with gypsum, calcium sulfate, to improve structure and nutrient capacity.   
  • The most feasible way to improve soils is increasing the organic fraction of the soil.  This includes humus, the stable fraction of organic matter, and organic matter serving as a food source for a variety of soil microorganisms and a nutrient supply for plants.  It isn’t possible/practical to build organic matter levels quickly in a producers field but over a period of years with proper management possible.  A one percent increase in organic matter will dramatically improve water and nutrient holding capacity as well as infiltration and aeration.  Again, on a smaller basis (flowerbeds, gardens) you can rapidly increase organic matter levels through composting, purchasing humus, and manures.  While not necessarily cheap, it is practical and easier to maintain higher levels for a small area.. 
  • There are many sources to increase organic matter depending on you resources and location:  manures, crop residues, compost, sewage sludge, etc.  The challenge is what is available; what is the cost; what fits your operation; and what is your operation.

Part II - Increasing Soil Organic Matter Levels
​​​​​​​Published August 11, 2019

As of this past Tuesday, the abnormally dry area of the state with the bullseye in our area has expanded. The recent rains should help at least some of the area. Corn, soybeans, and milo can all certainly use rain with developing seed. It is a horserace now to mature seed before a fall frost. Some models are predicting the possibility of an early fall, for the Corn Belt and Great Plains. If this happens, it would likely be least damaging to corn, potentially more for the milo crop, and probably quite serious for the soybean crop. Soybeans normally don’t need a frost to call it quits but often temperatures around forty degrees or the high thirties will shut them down. Before discussing how to increase organic matter, a response to a reader’s e-mail. Last week’s column mentioned that sewage sludge is one possible way to increase soil organic matter levels. The reader expressed some valid concerns. The sewage sludge should be properly composted and processed. Additionally, it is wise to have the sludge checked for heavy metals and other materials not affected by the composting process. These suggestions, while applying to lawn, landscaping, and gardens, is primarily aimed at production fields.

  • First, make sure to amend the pH on acid soils to the desired level through liming. Materials should be thoroughly incorporated and allowed adequate time to work. Acid soils will inhibit bacterial activity, favor fungi and cause problems ranging from fungal disease pressure to poor humus production. For high pH soils it is best to work around the pH level from a cost and practicality standpoint. If sections of the soil are sodic, high salt levels, consider the application of gypsum, calcium sulfate, to help replace sodium with calcium and improve soil structure and workability.
  • Much of the stable organic matter fraction will come from root mass. Depending on soil type, rainfall, and practicality, work with as diverse a crop rotation as possible. This will help minimize the need for tillage to control insects and diseases. Monocots, grass crops, have a more shallow, fibrous root system compared to dicots, which are tap rooted. They provide a more easily degradable food source for bacteria to decompose into humus. Keep the soil in plant production as much as practical.
  • Cover crops/green manures are also beneficial where practical and cost effective. The goal is to keep the soil in growing vegetation. They can be relatively cheap, crops like oats or rye, or pricey with species such as cowpeas, Austrian winter pea, and hairy vetch. Most can be grazed but to maximize the accumulation of residues to turn into organic matter/humus, grazing should be minimal. A green manure is different as it is tilled into the ground while actively growing.
  • Manures are also an excellent way to build organic matter but care must be taken as they can harbor weed seeds. Have a good idea of what you are using. However, manures are a readily available carbon source and source of phosphorus and nitrogen for microbes.
  • It provides a better soil environment for microorganisms if tillage can be minimized or even eliminated. Surface residue cover help conserve soil moisture and provide a more temperate environment for microorganisms and earthworms. Additionally, tillage and incorporation of residues speeds up organic matter decomposition and lowers organic matter levels.

Organic matter levels don’t increase overnight but can be increased over a period of five to ten years. One percent of organic matter can release up to thirty pounds of nitrogen and three to four pounds of phosphorus and sulfur each year. It can hold it’s weight in water, stabilize structure, and help prevent erosion.

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