Table 2. Biomass production, yield components (including ears number, grains per ear and thousand grain weight (TGW)), harvest index (HI), micronutrient reciprocal internal efficiencies (ZnRIE, FeRIE, MnRIE and CuRIE), grain micronutrient concentrations (GZnC, GFeC, GMnC and GCuC), straw micronutrient concentrations (SZnC, SFeC, SMnC and SCuC) and micronutrient harvest index (ZnHI, FeHI, MnHI and CuHI) of summer maize as affected by different yield ranges, cultivars and N levels.
| Parameters | Total | Yield ranges (Mg ha−1) | Cultivars | N levels | |||||||||
| <7.5 | 7.5–9 | 9–10.5 | >10.5 | YD | XY | ZD | FY | N-0 | N-low | N-opt | N-over | ||
| na 149 | 58 | 45 | 26 | 20 | 30 | 30 | 75 | 14 | 30 | 32 | 30 | 57 | |
| Biomass (Mg ha−1) | 13.2 | 10.2d | 14.0c | 14.9b | 17.5a | 9.7c | 14.2b | 13.5b | 16.4a | 10.3b | 13.9a | 14.5a | 13.6a |
| Ears number (104 ha−1) | 7.4 | 7.3a | 7.5a | 7.5a | 7.5a | 6.8b | 7.8a | 7.9a | 5.4c | 7.5a | 7.3a | 7.3a | 7.6a |
| Grains per ear | 425 | 379c | 420b | 477a | 500a | 429b | 352c | 416b | 616a | 352b | 444a | 450a | 439a |
| TGW (g) | 275 | 257b | 288a | 283a | 292a | 233c | 314a | 277b | 277b | 268a | 276a | 277a | 278a |
| HI (%) | 51 | 50c | 50c | 53b | 55a | 49b | 48b | 53a | 53a | 50a | 51a | 52a | 51a |
| ZnRIE (g) | 31.0 | 36.3a | 32.4a | 26.6b | 18.0c | 41.0a | 36.1b | 26.6c | 22.0d | 28.9a | 28.4a | 31.2a | 33.4a |
| GZnC (mg kg−1) | 16.3 | 16.7a | 17.4a | 16.6a | 12.2b | 17.6a | 16.0a | 16.4a | 13.6b | 15.2b | 15.2b | 16.6ab | 17.3a |
| SZnC (mg kg−1) | 20.0 | 24.4a | 20.2b | 17.1b | 10.7c | 29.0a | 23.7b | 16.1c | 13.8c | 18.2ab | 17.6b | 20.9ab | 21.8a |
| ZnHI (%) | 48 | 41d | 48c | 54b | 60a | 37b | 40b | 55a | 53a | 48a | 49a | 49a | 48a |
| FeRIE (g) | 64.4 | 68.6a | 64.6a | 59.7a | 57.4a | 66.8b | 54.4c | 61.2bc | 97.4a | 65.8a | 69.0a | 59.9a | 63.4a |
| GFeC (mg kg−1) | 15.8 | 15.9a | 16.2a | 16.6a | 13.8b | 17.6a | 13.9b | 15.9a | 16.0a | 13.4c | 15.5b | 16.0ab | 17.2a |
| SFeC (mg kg−1) | 62.6 | 63a | 62a | 61a | 66a | 58.6b | 46.6c | 61.9b | 109.4a | 63.3a | 69.6a | 58.3a | 60.6a |
| FeHI (%) | 23 | 21b | 23b | 27a | 22b | 23a | 22a | 24a | 14b | 19b | 21ab | 25a | 25a |
| MnRIE (g) | 18.1 | 17.8a | 18.3a | 17.5a | 19.0a | 17.8b | 16.5b | 17.3b | 25.9a | 16.8a | 18.3a | 18.0a | 18.7a |
| GMnC (mg kg−1) | 3.2 | 2.9b | 3.5a | 3.4a | 3.0b | 2.7c | 3.7a | 3.1b | 3.3b | 2.95c | 3.03bc | 3.35a | 3.28ab |
| SMnC (mg kg−1) | 19.0 | 17.3b | 18.4b | 19.9b | 23.9a | 17.4b | 14.4c | 19.3b | 30.2a | 16.8b | 19.4ab | 19.1ab | 19.8a |
| MnHI (%) | 16.0 | 15bc | 17ab | 18a | 14c | 14c | 20a | 16b | 11d | 16a | 15a | 17a | 16a |
| CuRIE (g) | 5.3 | 5.6a | 5.4a | 5.1a | 4.9a | 6.7a | 5.5b | 4.6c | 6.0ab | 4.5b | 5.4a | 5.4a | 5.7a |
| GCuC (mg kg−1) | 1.4 | 1.39b | 1.43b | 1.68a | 1.26b | 1.61a | 1.38b | 1.40ab | 1.34b | 1.24b | 1.27b | 1.57a | 1.55a |
| SCuC (mg kg−1) | 5.0 | 4.9a | 5.0a | 4.9a | 5.5a | 6.0a | 4.7b | 4.5b | 6.4a | 4.0b | 5.2a | 5.1a | 5.4a |
| CuHI (%) | 24 | 23b | 23b | 29a | 22b | 21b | 22b | 27a | 19b | 26a | 21b | 26a | 24ab |
na: number of observations. Means in a row followed by different lowercase letters are significantly different at different yield ranges, cultivars and N levels (P<0.05).