Table 4.
Soil starting nitrogen (Ninitial), nitrogen input (Ninput), nitrogen mineralization (Nmin), nitrogen uptake by plants (Nuptake), soil nitrate-N residual (Nresidual) in the 0–100-cm profile, nitrogen loss (Nloss), nitrogen recovery efficiency (NRE) and nitrogen use efficiency (NUE) as affected by nitrogen rate, plastic mulching and basal nitrogen application depth in the maize growing season in 2014 and 2015.
| Treatment | Ninitial (kg ha-1) | Ninput (kg ha-1) | Nmin (kg ha-1) | Nuptake (kg ha-1) | Nresidual (kg ha-1) | Nloss (kg ha-1) | NRE (%) | NUE (kg kg-1) | |
|---|---|---|---|---|---|---|---|---|---|
| 2014 | CK | 56 | 0 | 43 | 52 (0.8) d | 47 (0.8) d | – | – | – |
| T0 | 56 | 160 | 43 | 91 (5.5) c | 98 (7.9) c | 70 (5.3) a | 51 (3.3) d | 53 (1.5) b | |
| T1 | 56 | 160 | 43 | 109 (3.3) ab | 105 (6) bc | 46 (5) b | 66 (3.1) c | 62 (1.7) a | |
| T2 | 56 | 160 | 43 | 116 (8.6) a | 117 (8.2) a | 26 (16) d | 78 (10.1) a | 65 (3) a | |
| T3 | 56 | 160 | 43 | 105 (4) b | 112 (4.6) ab | 42 (5.3) bc | 68 (3.3) bc | 61 (1.4) a | |
| T4 | 56 | 160 | 43 | 115 (5) a | 114 (5.2) ab | 30 (4.5) cd | 76 (2.8) ab | 64 (1.5) a | |
| 2015 | CK | 68 | 0 | 49 | 55 (2.4) c | 64 (2.4) c | – | – | – |
| T0 | 68 | 160 | 49 | 87 (4.2) b | 109 (5.5) b | 81 (3) a | 46 (1.9) c | 53 (1.8) b | |
| T1 | 68 | 160 | 49 | 103 (7.3) a | 108 (3.6) b | 66 (10.6) b | 55 (6.6) b | 63 (2.1) a | |
| T2 | 68 | 160 | 49 | 117 (15.1) a | 123 (6.5) a | 37 (10.9) c | 73 (6.8) a | 66 (5.6) a | |
| T3 | 68 | 160 | 49 | 106 (8.1) a | 108 (5.4) b | 63 (6.2) b | 57 (3.9) b | 61 (1.6) a | |
| T4 | 68 | 160 | 49 | 108 (7.9) a | 127 (7.1) a | 42 (8.2) c | 70 (5.2) a | 63 (2) a | |
Means within columns followed by the same lowercase letters are not significantly different (P < 0.05) according to Tukey’s b tests. The numbers in parentheses are one standard error of the mean (n = 3).