TABLE 4.
Mean nitrate content on day 30 for each combination of year, amendment type, and mulch type
| Sample typea | Nitrate content on day 30 (mg/kg)b | Confidence interval |
|---|---|---|
| 2018.CPL.M | 171.5 ABC | 69–426.6 |
| 2018.CPL.NoM | 26.8 BCDE | 10.8–66.7 |
| 2018.HTPP.M | 220.8 ABC | 88.8–549.1 |
| 2018.HTPP.NoM | 15.9 DEC | 6.4–39.7 |
| 2018.PL.M | 520.6 A | 209.3–1295 |
| 2018.PL.NoM | 167.3 ABC | 67.3–416.2 |
| 2018.UN.M | 577.2 A | 232.1–1435.8 |
| 2018.UN.NoM | 128.3 ABS | 51.6–319.1 |
| 2019.CPL.M | 16.4 DEC | 6.6–40.9 |
| 2019.CPL.NoM | 20.9 BCDE | 8.4–51.9 |
| 2019.HTPP.M | 242.9 AB | 97.6–604.1 |
| 2019.HTPP.NoM | 120.8 ABC | 48.6–300.4 |
| 2019.PL.M | 18.1 BCDE | 7.3–44.9 |
| 2019.PL.NoM | 7.3 DE | 2.9–18.1 |
| 2019.UN.M | 81.2 ABCD | 32.7–202.1 |
| 2019.UN.NoM | 2.6 E | 1–6.4 |
a
Sample types are described as “year/amendment type/mulch type.” CPL, composted poultry litter; HTTP, heat-treated poultry pellet; PL, poultry litter; UN, no biological amendment; M, black plastic mulch; NoM; no mulch.
b
Different uppercase letters indicate statistically significant (P < 0.05) differences in mean values for specified combinations of year, amendment type, and mulch type.