Dairy One

Dairy One Pre Sidedress Nitrogen Testing and Guidelines
Pre Sidedress Nitrogen Testing (PSNT) is used to determine if sidedress N is needed on corn with a history of manure or sod incorporation. The PSNT measures potentially mineralizable organic N in the soil to determine the likelihood of a yield response from sidedressed N.

PSNT's should be run on corn fields two or more years after sod plow down where the manure rate is uncertain or may not meet the N requirements of the crop. A PSNT should also be run if N mineralization rates are expected to be higher than average (e.g., warm moist spring).

PSNT's should not be run on corn fields that had broadcast N applications pre plant or early post plant since nitrate picked up from broadcast fertilizer could overestimate true N mineralization potential.

PSNT's should not be run on first year corn after a grass sod with starter N since a response to sidedressed N is very unlikely unless the soil has a very high yield potential (Hamlin, Genesee, etc).

PSNT is not needed for first year corn following an alfalfa grass mixture since a response to sidedressed N is highly unlikely.

Sampling Guidelines

1.  Limit sample area to < 15 acres.

2.  Take a separate sample for areas that are different.
     a. hybrid, population, growth stage, history, management, etc.

3.   Sample when corn is 6 - 12 inches tall.

4. Wait 2-3 days after significant rainfall (due to nitrate leaching).

5. Sample between rows taking care to avoid the starter band.

6. Sample to a depth of 12 inches.

7. Dry the sample immediately to stop mineralization and send the
samples to:

Dairy One Soils Lab
730 Warren Road
Ithaca, NY 14850

8. Pick up points are available in some areas.

9. Contact Dairy One Customer Service to find out if there is a pick up
point near you. Phone: 1-800-344-2697 ext. 2172.

10. Dairy One will report results within 24 hours after receiving your samples
if they arrive Monday thru Friday.

PSNT Interpretation

PSNT ppm Nitrate-N	Likelihood of an economic response to sidedressed N	N Guidelines
> 25	Low	No additional N needed
21-24	About 10%	Consider 25-50 lbs N/Acre if you expect a yield response
<21	High	Apply sidedress N per Cornell N guidelines for corn

1.	When the PSNT is < 21.
	a.	Add extra N if you expected to need sidedress N (i.e., field received less manure than needed to meet crop N requirement).
	b.	Check field history & manure applications if you didn't expect to need sidedressed N.
		i.	Low mineralization of organic-N early in the season may be off set when warm moist soil conditions resume.
			No additional N may be needed. Double check N requirements and only apply extra N if needed.
		ii.	PSNT may help identify those fields that did not receive the planned for amount of manure.

Additional Resources;
NYS Corn N Calculator: nmsp.css.cornell.edu/nutrient_guidelines