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One simple test can provide valuable information on two fronts – nitrogen use efficiency by the corn crop, and potential toxicity as a feed.  To obtain meaningful results, a proper sample must be taken, timed between ¼ milk line and 3 weeks after black layer.  Cut an 8 inch long section of corn stalk from 6 inches above ground level, from a minimum of ten plants across a representative area.  Stalks can be chipped or shredded, or cut into 2 inch lengths with pruners, but should be submitted to the lab as soon as possible to avoid sample decomposition.

Result Interpretation:

  • Nitrogen Use Efficiency 
    • < 0.07% (< 700ppm) - Nitrogen deficiency symptoms likely, high probability that nitrogen deficiency limited the yield
    • 0.07% - 2.00% (700 - 2,000ppm) - Optimal target range for nitrogen management
    • > 2.00% (> 2,000ppm) - Nitrogen supply in excess of crop requirements, indicating potential for economic or environmental losses of Nitrogen
  • Feed Guidelines
    • < 0.12% (< 1,200ppm) - Generally safe
    • 0.12% - 0.23% (1,200 - 2,300ppm) - Use caution
    • > 0.23% (2,300ppm) - Dangerous, death and abortions can occur in beef cattle and sheep

Note: Ensiling corn silage reduces the nitrate-nitrogen levels.


Corn silage has already begun in many locations, but monitoring whole plant moisture is especially important this year as maturity and dry-down are variable and atypical due to this year’s earlier drought conditions followed by frequent rains.  Gauging cutting date by kernel milk line is not suggested, as it can be variable by variety, and may underestimate whole plant moisture where plants are drying down rapidly.

Maximizing quantity and quality of silage can be achieved by harvesting at the correct whole plant moisture for the particular storage type:

  • Bunkers: 65% - 70%
  • Bags: 60% - 68%
  • Towers: 64% - 68%
  • Oxygen Limiting Storage: 58% - 62%


SGS is proud to exhibit at Canada's Outdoor Farm Show, being held September 13 - 15 in Woodstock, Ontario. You can find our experts at booth N-162, 1st Lane North. Click here for more details.

For more information, please contact:

Jack Legg, CCA-ON
Branch Manager, Agronomist
Guelph, Ontario N1H 6T9
503 Imperial Rd. N., Unit 1
t: +01 519 837 1600