Silking is a Great Time for Tissue Testing

Tissue sampling is a good tool for monitoring plant health during the growing season. However, it is important to note that tissue sampling is typically not a good indicator of potential response to in-season rescue applications. Tissue sampling should instead be used in tandem with soil sampling to identify trends and make future management decisions.

To identify trends over time, it is best to sample at the same growth stage and in the same area from year to year. Keep in mind that soil conditions such as compaction, weather, and hybrid type may all have an effect on tissue test results. Research from Iowa State University shows that a P tissue test at silking is best, while K tests work equally well with young plants or at silking. It is generally accepted that tissue testing at silking helps to monitor a soil fertility management program.

For leaf tissue testing, harvest the corn leaf below the ear at silk emergence before the silks turn brown. Do not include portions of the leaf sheath (collar). It is best to sample 10-20 plants to give a representative sample. Samples should be placed in a loose paper bag (like a grocery bag) to allow for drying; do not seal in a plastic bag. When the sample is about as dry as cured hay, it is ready for mailing. Check with a given testing center to see if there are any further shipping or sample preparation protocols. Some area testing centers along with contact information are listed below:

Regional testing labs available to process plant samples:

• AgLab Express
  3600 S. Minnesota Ave.
  Sioux Falls, SD 57105
  605.271.9237
  Website
• AgVise Laboratories, Inc.
  902 13th St. N.
  PO Box 187
  Benson, MN 56215
  320.843.4109
  Website
• Midwest Laboratories
  13611 B St.
  Omaha, NE 68144
  402.334.7770
  Website
• Next-Level Ag, LLC
  617 N. Pine Ave.
  Alpena, SD 57312
  605.849.5227
  Website
• Ward Laboratories
  4007 Cherry Ave.
  PO Box 788
  Kearney, NE 68848
  308.234.2418
  Website

Testing center summaries will report tissue sample results along with suggested sufficiency ranges for macro and micro-nutrients. Keep in mind that nutrient deficiencies observed with tissue tests may not always result in yield losses. A tissue test can indicate a deficiency in the plant that is not necessarily in the soil. In this case, it becomes necessary to understand the big picture…what environmental conditions are obstructing nutrients from entering the plant? When done correctly, tissue testing over time can complement soil testing to help provide a grower with a useful picture of their soil fertility management program.

For Further Information:

• Mallarino, A. 2016. Research Shows a Role for Phosphorus and Potassium Tissue Testing in Corn. Integrated Crop Management News. Iowa State University Extension, Ames, IA.
• Thom, W.O., J.R. Brown, C.O. Plank. 1991. Sampling for Corn Plant Tissue Analysis. National Corn Handbook. NCH-15. Iowa State University Extension. Ames, IA.

Source: Jonathan Kleinjan, iGrow