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Sampling Drought Damaged Crops for Nitrates
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July 24, 2002
With this year’s hot, dry summer and drought conditions we have received
several calls regarding sampling drought damaged corn and sudan grass for
nitrate. The correct sampling procedure is a very important part of any
analysis that Ward Laboratories, Inc. performs and we offer the following
tips:
- Cut the plant samples at the height you
will be swathing, cutting or the height that you expect the
livestock to graze.
- Pick plants that accurately represent
your field. More than one sample may be necessary if various
degrees of stress are evident within the field.
- Cut at least 10 plants per sample.
- Nitrate is highest in the lower stalk.
We suggest cutting off the bottom 8-12 inches of stalk for a
separate nitrate test.
- Ward Laboratories, Inc. will chop and
grind the sample at the laboratory.
- If it rains and you are grazing the
corn or sudan grass, remove the livestock immediately. The
nitrate levels in the plant can increase rapidly and we
recommend re-sampling to check for increased nitrates following
a rain.
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This summer, high levels of nitrate-nitrogen have been found in
drought-damaged crops. The table below outlines animal response to
nitrate-nitrogen concentration. If you have additional questions, please
contact the professionals at Ward Laboratories, Inc.
Animal Response to Nitrate-Nitrogen Concentration
NO3-N ppm Comment:
Less then 1400 Safe.
1400 – 2100 Marginal, use caution when feeding. Can cause reduced milk
production, abortions, and low rate of gain. It would be best to limit daily
use to 1/2 of the
total daily dry matter intake.
2100 – 3000 Feeds in this range should be limited to 1/3 of the total daily
dry matter intake.
3000 – 4000 Feeds in this range should be limited to 1/4 of the total daily
dry matter intake.
4000 – 5000 Feeds in this range should be limited to 10-15% of the total
daily dry matter intake.
Greater than 5000 Do not feed – Death may occur.
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