Table 5. Levels of Soil Nitrogen Resulting from Nitrate and Ammonium Ions in Different Nitrogen Treatmentsa.
| NO3– -N (mg/kg) |
NH4+-N (mg/kg) |
|||||
|---|---|---|---|---|---|---|
| treatmentb | July 2 | July 10 | July 18 | July 2 | July 10 | July 18 |
| control | 12.46d | 22.75a | 15.87a | 8.17b | 8.03ab | 22.58c |
| UREA100% | 15.45d | 22.37a | 17.51a | 6.03b | 7.62b | 24.00c |
| UREA80% | 13.67d | 23.41a | 17.15a | 5.38b | 8.75ab | 24.52c |
| SSNF100% | 76.81a | 21.77a | 17.68a | 11.90a | 8.90ab | 25.76bc |
| SSNF80% | 36.07c | 21.95a | 16.21a | 5.26b | 9.62a | 24.45c |
| BBW100% | 57.71b | 23.62a | 18.47a | 7.08b | 8.15ab | 28.43ab |
| BBW80% | 37.31c | 22.58a | 16.16a | 7.38b | 8.44ab | 29.25a |
a
Means within a column followed by different letters were significantly different based on analyses by one-way ANOVAs followed with Duncan tests for mean separation (p < 0.05).
b
Control (no fertilizer added), UREA100% or UREA80% (100 or 80% portions for urea), SSNF100% or SSNF80% (100 or 80% portions for water-soluble, slow-release nitrogen fertilizer), BBW100% or BBW80% (100 or 80% portions for a mixture of 70% SSNF and 30% urea).