Pre-Side Dress Nitrate Nitrogen PSNT samples should be taken when corn plants are 6 to 12 inches tall, usually four to six weeks after planting. PSNT samples are collected only to a depth of one foot. Results of the PSNT are interpreted using a critical value of 21 ppm nitrate-N. Fields testing above 21 ppm N most likely will not respond to additional N. Fields testing below 21 ppm N will likely respond to additional N. Corn Nitrogen Recommendations | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| SOIL TEST NITRATE N | PSNT RESULT N (ppm) | **SOIL YIELD POTENTIAL | |||
| (1) Very High | (2) High | (3) Medium | (4) low | ||
| Application Rate (lb/a) | |||||
| > 21 | 0 | 0 | |||
| 20-18 | 60 | 40 | |||
| 17-25 | 100 | 40 | |||
| 14-13 | 125 | 80 | |||
| 12-11 | 150 | 80 | |||
| < 10 | 160*** | 120*** | |||
*Note: When corn follows alfalfa, the maximum N recommendation is 40 lb N/a for all PSNT results less than 21 ppm N
**To determine a soil's yield potential for a specific soil type, consult the UWEX publication "Soil Test Recommendations for Field, Vegetable and Fruit Crops" (A2809)
***No adjustment made to original Corn N recommendations
For laboratory specific information regarding Nitrate Analysis, test packages/supplies, technical bulletins, sampling guides or feature reports please contact one of our laboratories nearest you listed below:
Laboratory Locations:
| AgSource Laboratories - Bonduel, WI | 715-758-2178 | bonduel@agsource.com |
| AgSource Laboratories - Ellsworth, IA | 515-836-4444 | ellsworth@agsource.com |
| AgSource Laboratories - Jerome, ID | 208-324-7511 | jerome@agsource.com |
| AgSource Laboratories - Lincoln, NE | 402-476-0300 | lincoln@agsource.com |
| AgSource Laboratories - Umatilla, OR | 541-922-4894 | umatilla@agsource.com |
