Friday, October 10, 2014

What Causes Lighter Grain Test Weight?

A recent question by a few in the Northern part of the Burrus Footprint: Why is my grain test weight lighter than normal?

Test weight is a measure of grain bulk density (pound of grain per volumetric bushel) and sometimes can be a measure of general grain quality.  There is not much evidence that grain test weight is related to grain yield; therefore, higher yields don't necessarily have higher test weights.  Also, the higher the moisture (immature), the lower the test weight.

Of course, we all know that there can be corn hybrid differences or physical characteristics such as size, shape, and "slickness" of the outer kernel layer that cause differences in test weight.  Grain test weight can also be affected by how kernels are packed in a container (tester), which can be influenced by kernel shape.

So, what could of cause lower grain test weight in 2014?

1. Later planting

2. Corn stress during grainfill can cause lower test weight:
  • Drought
  • Hail
  • Insects
  • Foliar disease
  • Below normal temperatures during grainfill
  • Cloudy days?
  • Nitrogen deficiency (other nutrient deficiency?)

2.  Freeze or frost to immature corn plants (before black layer) can cause plant death and, thus, less test weight

3.  Stalk rots

4.  Ear rots

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