Table 2.
Ammonium loss (%) during a 28-day incubation and NOx–-N production rate in Horsham soil (pH 8.8). All samples were treated with the fertiliser (NH4)2SO4 at a rate of 100 mg N kg-1.[a,b,c].
| Treatment | NH4+-N loss/% | NOx–-N production rate[d] | ||
|---|---|---|---|---|
| Day 7 | Day 14 | Day 28 | ||
| (I) Incubations at 25 °C | ||||
| (NH4)2SO4-control | 68.5 ± 2.4 | 100 ± 2.7 | 100 ± 2.7 | 3.6 ± 0.1 |
| DMPP | − 2.1 ± 3.2 | 1.4 ± 2.7 | 8.9 ± 3.2 | 0.8 ± 0.1 |
| N002 | 17.9 ± 6.9 | 44.5 ± 7.2 | 90.4 ± 9.7 | 3.4 ± 0.1 |
| N013 | 23.4 ± 5.4 | 40.0 ± 4.3 | 72.2 ± 4.8 | 2.8 ± 0.1 |
| N014 | 38.7 ± 5.3 | 84.3 ± 5.6 | 100 ± 3.2 | 3.9 ± 0.1 |
| N015 | 47.4 ± 2.9 | 88.9 ± 4.0 | 100 ± 3.6 | 3.8 ± 0.1 |
| N016 | 24.9 ± 3.0 | 44.2 ± 3.3 | 70.9 ± 3.9 | 2.7 ± 0.1 |
| N017 | 30.6 ± 5.5 | 35.1 ± 5.1 | 65.8 ± 5.2 | 2.5 ± 0.1 |
| (II) Incubations at 35 °C | ||||
| (NH4)2SO4-control | 45.9 ± 1.7 | 81.6 ± 3.7 | 98.0 ± 2.0 | 4.1 ± 0.1 |
| DMPP | 18.9 ± 2.8 | 32.3 ± 4.1 | 64.5 ± 12.7 | 2.7 ± 0.5 |
| N002 | 8.8 ± 5.5 | 40.3 ± 5.4 | 71.6 ± 22.9 | 3.1 ± 0.8 |
| N013 | 18.7 ± 5.5 | 48.0 ± 5.3 | 61.2 ± 14.2 | 2.8 ± 0.7 |
| N014 | 15.7 ± 5.7 | 39.8 ± 6.6 | 79.7 ± 9.4 | 3.8 ± 0.3 |
| N015 | 37.4 ± 5.4 | 77.0 ± 6.2 | 100 ± 6.3 | 4.3 ± 0.1 |
| N016 | 22.3 ± 4.3 | 42.3 ± 4.6 | 83.7 ± 6.1 | 3.9 ± 0.1 |
| N017 | 18.9 ± 2.8 | 32.3 ± 4.1 | 76.2 ± 2.1 | 3.7 ± 0.1 |
[a] Application rates are 10 mol% of applied fertiliser N. [b] Ammonium loss was calculated from NH4+-N concentrations detected in samples at each timepoint. [c] Mean values (n = 3); errors are standard errors of the mean. [d] After 28 days; in mg NOx–-N/kg soil/day.