Skip to main content
ARS Home » Midwest Area » Morris, Minnesota » Soil Management Research » Research » Publications at this Location » Publication #106017
Title: EVALUATION OF SOIL NITRATE TESTS FOR PREDICTING CORN NITROGEN RESPONSE IN THE NORTH CENTRAL REGION

Author
item BUNDY, L - UNIVERSITY OF WISCONSIN
item WALTERS, D - UNIVERSITY OF NEBRASKA
item Olness, Alan

Submitted to: Extension Publications
Publication Type: Government Publication
Publication Acceptance Date: 3/1/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Nitrogen is most often the nutrient limiting crop production. A need exists for an accurate soil test of nitrogen (N). Scientists in the Corn Belt studied the ability of the nitrate soil test to predict fertilizer-N need. Soil samples were taken at planting time and after the crop had reached the 5-leaf growth stage. These samples were tested for nitrate-N content. The results show that the nitrate test is a good indicator of fertilizer-N need. Soil samples taken after the crop has emerged are better indicators of fertilizer-N need than those taken before planting. Soils with pH values near 6.7 tend to produce more nitrate N than more acidic or alkaline soils. Also soils with medium textures tend to produce more nitrate-N than finer or coarser textured soils. By testing soils in the spring and waiting to apply N after the crop has emerged, farmers can add only as much N as is needed. Such practices will minimize environmental pollution and result in greater profitability.

Technical Abstract: The prediction of nitrogen (N) sufficiency in soil for optimal crop production has been one of the most elusive objectives of agricultural research. The CSREES N. Central Regional Committee 218 examined the pre-plant and pre-sidedress nitrate tests (PPNT and PSNT) for their suitability as indicators of soil N sufficiency. Following a uniform protocol, tests were conducted at 307 sites in the 12-state region. Maize (Zea mays L.) was grown with an N rate deemed more than adequate for maximal production and with only starter fertilizer in replicated field studies. Soil cores were extracted to a depth of 60-cm at planting and again at the 5-leaf growth stage and examined for nitrate-N concentration. Grain yields of non-fertilized sites were expressed as a percentage of their fertilized counterparts and then regressed against the PPNT and PSNT using linear- and quadratic-response-plateau models. Highly significant correlations were obtained with those of the PSNT > PPNT except when alfalfa was the previous crop. When alfalfa was the previous crop, no fertilizer N response was detected. For the 60-cm depths, critical levels of nitrate-N averaged 9.3 (PPNT) to 12.0 (PSNT) ug per g for the linear- and from 16.7 (PPNT) to 17.9 (PSNT) ug per g for the quadratic-response- plateau models. Soils with pH between 6.0 and 7.0 and soils with medium textures tended to have greater PPNT and PSNT values than other soils in the study; they also had the greatest changes in nitrate-N between PPNT and PSNT.