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Interesting Trends in Forage and Crop Residue Analysis during July and August

August 30, 2012

Dr. Shane Gadberry, Professor – Animal Science


Given the drought situation, following the type of samples submitted to the UA diagnostics laboratory and the requested analyses has been interesting.  The following bullet points highlight July and August trends.


  • County agents have been pre-screening crop residue samples for nitrates using a qualitative test.  This appears to be keeping the number of samples that actually make it to the lab and testing high for nitrates at a minimal.
    • 6 out of 37 corn stover and 2 out of 29 sorghum stover samples tested above 1,500 ppm nitrate-nitrogen.  The maximum was 2,672 ppm for corn stover and 6,000 ppm for sorghum stover.
  • Clientele submitting samples are more concerned about nitrates than nutrient composition
    • Far fewer submissions are requesting a protein and fiber analysis in addition to the nitrate analysis.  Thus far, 7 out of 37 corn stover and 8 out of 29 sorghum stover samples were submitted for nutrient composition determination.
  • Producers need to be just as concerned about nutrient composition as nitrates
    • Of the samples submitted for nutrient composition, the range of protein in corn stover was 3.3% to 8.4% and the range for sorghum stover was 3.3% to 14.6%.  The maximum acid detergent fiber content was approximately 1.5 times the minimum.  Very low protein and very high fiber roughages will be detrimental to herd production if not fed as part of a balanced ration.  In the midst of high feed costs, balancing a ration based on a forage test makes the most sense.
  • Phones calls received for how to feed poultry litter out-number the samples submitted for nutrient analysis.
    • The 19 litter samples received at the lab since June have been running higher than usual for protein, averaging 26% with a minimum of 18% and maximum of 41%.  The total digestible nutrients averaged 48%, close to the typical average of 49%.  The minimum was 42% and maximum was 56%.
  • Less fertilization due to dry weather may be associated with the small percentage of sorghum-sudan and johnsongrass hay and pasture samples testing high for nitrate.
    • Of the 28 pasture samples tested for nitrates, maximum nitrate-nitrogen was 1,696 ppm.
    • Hay samples testing greater than 1,500 ppm nitrate-nitrogen were 5 out of 67 for combined sorghum-sudan and johnsongrass results.



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