Ag Instructor Vic Martin: Area Soils, Nutrients, and Wheat

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Great Bend Tribune
Published August 23, 2020

The Drought Monitor shows little change from last week, while that may change as there is little rain in the forecast, the dew point is lower, and temperatures are seasonal.  For corn producers it will help with maturity and drydown.  It will have a negative effect on milo and soybean seed production if this dry period lasts for more than two weeks.  The six to ten day outlook (August 26 to 30) has normal to above normal precipitation and above normal temperatures for the state.  Looking out eight to fourteen days (August 28 to September 3) indicates above normal precipitation and normal temperatures.  Last week the Extension Districts Crops Agent’s article discussed wheat and fertility needs for the upcoming season.  Most of it was fine.  Soil testing, cautions and caveats were fine but the information didn’t take into account the uniqueness of the soils in our area.  Today, let’s discuss the fertility needs as affected by soil type.

First, the uniqueness of the soils in the Barton area.  I apologize but this will be brief.  The easiest thing to do is break soils down into north and south of the Arkansas River.  Generally speaking, the soils south of the river are sandy – sandy loams and loamy fine sands.  They are low in organic matter and clay.  North of the river, overall, the soils are predominantly silt loams with some heavier clay loam soils and generally a bit higher in organic matter.  Organic matter and clay determine the soils ability to hold water and positively charged nutrients such as potassium, ammonium, and iron.  Organic matter also has the ability to hold and retain negatively charged nutrients such as nitrate, sulfur, and chloride.  Sandier soils low in organic matter are more challenging to manage and negatively charged nutrients leach below the root zone more easily.  Now what does this mean for specific nutrients and wheat? 

  • You are more likely to retain nutrients north of the river, especially with the recent heavy rains.  But for both the appropriate soil test can tell you what you have.  If you don’t soil test, at the least determine how much you removed for the last harvest, what you expect yields to be, and determine nutrient needs.  Now for two specific nutrients.
  • Sulfur containing amino acids are part of plant proteins.  Therefore if you lack sulfur it hurts yield and protein levels.  Soils north or south of the river may likely be deficient but especially south of the river.  This is correctable but don’t go crazy applying it for two reasons.  First, it’s not free.  Second, as an anion, it leaches easily and can be lost.  Fortunately, it may be applied over winter and be readily available,  Many sandy soil wheat producers don’t soil test as they know they need it and apply sufficiency levels every year at planting.
  • Chloride is also an anion and especially lacking on sandy soils.  It is important for a variety of reasons but the most critical is plant health.  Last week’s extension article stated deficiencies are worse in eastern Kansas and that is sort of true if you are speaking of the western third of the state.  But here deficiencies are fairly common, especially on sandy soils.  The major reason for the deficiency actually has to do with potassium.  Soils here were high in native potassium so we didn’t need to fertilize for it.  That is changing.  This affected chloride levels as most potassium is applied as potassium chloride.  So without know it, producers back east prevented chloride deficiency and here we didn’t.  Easily correctable and not expensive.  However, a soil test simply tells you if you need it based on a range and not an actual number.

           

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