Quirine Ketterings1, Jonathan Klapwyk2, Joseph R. Lawrence1, and Karl J. Czymmek3. (1) Cornell Univ, 817 Bradfield Hall, Ithaca, NY 14853, (2) Univ of Guelph, Kemptville C, 830 Prescott St, Kemptville, ON K0G 1J0, (3) Cornell Univ, ProDairy, 818 Bradfield Hall, Ithaca, NY 14853
Nitrogen (N) prices and environmental concerns have caused many corn (Zea mays L.) producers and advisors to rethink their current N management practices. These past 5 years, laboratory and field trials were conducted in NY to evaluate the performance of the Illinois Soil N Test (ISNT) in identifying whether or not N addition was needed for corn silage. Initial test results showed the need for temperature control in the laboratory and resulted in a modification of the procedure to include enclosed boxes. Evaluation of the ability of the modified ISNT procedure in detecting increases in organic N upon compost and manure application showed an increase in ISNT over time consistent with N credits from manure currently employed for N management in NY. However, to obtain an estimate of potential N release from readily available organic N sources, sampling should not take place within 2 wk after manure (or fertilizers that contain ammonium) application. Results of the first 3 yr of field trials showed that soil samples taken to 20-cm depth around corn planting time and analyzed for both ISNT and organic matter (LOI) can be used to predict the need for side-dress N for corn silage in NY. Work is ongoing but results to date show that possibly the biggest advantage in implementation of the ISNT, and motivation for further development of this test, lies in its potential for use by corn producers who currently apply additional N (beyond starter N) as pre-plant N. This may be possible since ISNT samples can be taken early in the season (before or at planting) rather than in the middle of growing season.