Some parts of the country have recently experienced heavy rains. Producers in these areas may have concerns about nitrogen loss in corn fields. Nitrogen losses occur by two main pathways: denitrification (gaseous loss of N) and leaching of nitrate from
Most nitrogen that is lost from a field is in the nitrate form during wet conditions. Time of transformation to nitrate is dependent on the type of N fertilizer applied. Anhydrous ammonia is less susceptible to loss since it converts to nitrate rather slowly.
Soils have been warm enough that some transformation to nitrate may have already occurred this year depending on application date. However, the
Since there are no absolute tests that can tell the N status a point system developed years ago by the University of Minnesota and modified to Ohio conditions has been useful. This system asks a series of questions and assigns a point value depending upon the answer. The probability of a response to additional N increases with more points. The questions and points are given below:
FACTOR 1: What N product was used?
FACTOR 2: When was the majority of the fertilizer N applied?
FACTOR 3: What has been the field soil moisture status the past month?
FACTOR 4: What is the crop’s current condition?
Total the score for the four factors and use the following guidelines:
The “re‑evaluation” option is only viable until you no longer have side dressing options. Illinois research from the 1990’s found that 50 lb. N/acre as a supplemental N rate was satisfactory for a wide range of conditions. While a total score of 17‑18 would merit a 40 lb./acre N recommendation. A total score of more than 18 may require a higher N rate. Losing 100% of the N fertilizer applied via denitrification or leaching is extremely unlikely and so a reapplication of the total amount of N for the season is not recommended.
Source: Ohio State University Extension
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