A pre-sidedress nitrogen test is an in-season test used to determine if additional nitrogen should be applied
to a crop during the growing season. Use of the test avoids the use of excess nitrogen fertilizers, thus
eliminating potential run-off and provides cost savings in labor and chemicals. It is especially useful in
soils that are high in organic matter or have had a cover crop or manure turned under before planting. This
test has been used successfully with corn, potatoes, peppers and some cucurbits. This research update
looks at its use in fall cabbage. The test was done in 27 fields throughout the Northeast. The fields had
been previously planted with sweet corn that was disked in after harvest. Five-week-old cabbage
transplants were planted in the soil the last week of July or the first two weeks of August. PSNT tests of
NO3-N were taken two weeks after planting.
Results showed that the critical soil concentration of NO3-N levels was 24 ppm NO3-N. In other words, if
your individual soil test reveals a number greater than 24 ppm NO3-N than further applications of nitrogen
fertilizer are unnecessary and will not increase yields. If your individual soil test reveals a number less than
24 ppm NO3-N than the addition of nitrogen will increase yields. This critical number is the same number
used for both sweet corn and field corn and is only slightly higher than the number used for celery and
lettuce. The usual nitrogen recommendation in the Mid-Atlantic States is for 112 to 168 ppm N/ha. If a
PSNT shows NO3-N concentrations are less than 9 ppm than adding a full complement of fertilizer is
recommended. If your soil test reveals a number in the range of 10 to 23 ppm, then you could reduce the
amount of nitrogen you apply by as much as 25 to 50%.
Note: This research was conducted in the state of New Jersey, Connecticut, Delaware, and New York.
Also, this is just a summary of the work. This is not an implied endorsement.
Original Source: Heckman, J.R., T. Morris, J.T. Simms, J.B. Sieczka, U. Krogmann, P. Nitzsche, and D.
Ashley. 2002. HortScience. 37(1):113-117.
ADAPTED BY ANNE CARTER UMASS VEG. CROPS MANAGEMENT & FOOD SYSTEMS
