Why test?

Soil nitrogen testing allows nitrogen fertilizer recommendations to be adjusted for field-specific conditions that can influence corn nitrogen need. Both economic and environmental benefits can be gained through the use of the tests. Economically, fertilizers dollars can be saved by avoiding nitrogen applications in excess of crop needs. Environmentally, the potential for nitrate movement to groundwater can be reduced by avoiding over-application of nitrogen fertilizer.

Reporting and Analysis

Both reports provide a laboratory analysis of nitrate-N. Pre-plant reports will provide nitrogen recommendations based upon the field, crop and fertilizer information provided on the submission form. Pre-sidedress reports will provide a general nitrogen credit recommendation. View a pre-plant sample report or a pre-sidedress sample report.

Sampling

Pre-plant soil sampling should be done to a depth of 2 feet in early spring. Pre-sidedress sampling should be done to a depth of 1 foot when corn is 6 to 12 inches tall. Please see Chapter 6 of A2809 for detailed sampling instructions.

References

Corn PPNT: Ehrhardt, P.D., and L.G. Bundy. 1995. Predicting nitrate-nitrogen in the two- to three-foot soil depth from nitrate measurements on shallower samples. J. Prod. Agric. 8:429-432.

Winter wheat PPNT: Bundy, L.G., and T.W. Andraski. 2004. Diagnostic tests for site-specific nitrogen recommendations for winter wheat. Agron. J. 96:608-614.