Table 2.
Changes in soil chemical and physical measures after long-term elevated atmospheric CO2 conditions, N-fertilization or the combination of treatments, at four soil depth intervals.
| Soil depth interval | Soil factor | ANOVA F test | Effects of CO2 | Effects of N-fertilization | CO2 × N fert interaction |
|---|---|---|---|---|---|
| FF | Nitrate (ppm) | 0.2546 | … | ↑ (0.0646) | … |
| pH | 0.0319 | ↓ (0.0071) | … | (0.0451) | |
| Organic matter (%) | 0.7959 | … | … | … | |
| Water content (%) | 0.1680 | … | … | … | |
| P (ppm) | 0.7699 | … | … | … | |
| Ca (meq/l) | 0.0885 | ↓ (0.0148) | ↑ (0.0094) | … | |
| K (meq/l) | 0.0891 | … | ↓ (0.0418) | … | |
| 0–2 cm | Nitrate (ppm) | 0.1944 | … | ↑ (0.2270) | … |
| pH | 0.0183 | ↓ (0.0245) | ↓ (0.0091) | … | |
| Organic matter (%) | 0.0016 | ↓ (0.0028) | ↑ (0.0006) | … | |
| Water content (%) | 0.0487 | ↑ (0.0154) | … | … | |
| P (ppm) | 0.0077 | ↓ (0.0314) | ↑ (0.0087) | (0.0038) | |
| Ca (meq/l) | 0.0721 | … | ↑ (0.0094) | … | |
| K (meq/l) | 0.2359 | … | … | … | |
| 2–5 cm | Nitrate (ppm) | 0.1463 | … | ↑ (0.0228) | … |
| pH | 0.0167 | … | ↓ (0.0037) | (0.0649) | |
| Organic matter (%) | 0.3501 | … | … | … | |
| Water content (%) | 0.2442 | … | … | … | |
| P (ppm) | 0.2513 | … | … | … | |
| Ca (meq/l) | 0.4084 | … | … | … | |
| K (meq/l) | 0.5252 | … | … | … | |
| 5–10 cm | Nitrate (ppm) | 0.0952 | … | ↑ (0.0150) | … |
| pH | 0.0016 | … | ↓ (0.0004) | (0.0047) | |
| Organic matter (%) | 0.7071 | … | … | … | |
| Water content (%) | 0.2123 | … | … | … | |
| P (ppm) | 0.5932 | … | … | … | |
| Ca (meq/l) | 0.3446 | … | … | … | |
| K (meq/l) | 0.1108 | … | … | … |
Values in each row are the p value from the factorial ANOVA F test, followed by the direction of the effect and the least square means pairwise t text p value for that factor. Treatment effects are only shown for ANOVA F test statistics where p ≤ 0.10, and the treatment effect was p ≤ 0.05. Although not significantly different in the top three soil depth intervals, nitrate analysis is shown since this was an experimentally manipulated variable.