Table 3.
Effect of organic compost and inorganic nitrogen fertigation on the concentration of nutrients in recent fully expanded leaves sampled at harvest spinach.
| Treatments | Leaf macronutrients (mg·g−1) |
Leaf micronutrients (μg·g−1) |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| N | P | K | Ca | Mg | Fe | B | Cu | Mn | Zn | |
| OC | 5.98 b1 | 0.83 | 7.49 | 1.02 b | 0.78 b | 134.5 | 34.5 | 16.0 | 123 b | 86.5 b |
| OC + AS | 7.82 a | 0.83 | 7.47 | 1.37 a | 0.92 a | 143.5 | 46.5 | 12.2 | 218 a | 101.5 a |
| OC + AN | 8.00 a | 0.95 | 7.88 | 1.34 a | 0.99 a | 134.5 | 38.0 | 10.9 | 145 b | 94.0 b |
| Significance | ∗∗∗ | NS | NS | ∗∗ | ∗∗ | NS | NS | NS | ∗∗∗ | ∗ |
| Recommended range | ||||||||||
| Mills and Jones (1996) | 4.00–6.00 | 0.30–0.60 | 5.00–8.00 | 0.70–1.20 | 0.60–1.00 | 60–200 | 25–60 | 5–25 | 30–250 | 25–100 |
| Campbell (2000)2 | 4.00–6.00 | 0.30–0.50 | 3.00–8.00 | 1.00–1.50 | 0.40–1.00 | 50–200 | 25–60 | 5–15 | 25–200 | 20–75 |
1
Means followed by different letters within a column are significantly different. ∗, ∗∗, ∗∗∗ Significant at p < 0.05, 0.01 and 0.001 levels, respectively. NS = not significant.
2
Values to spinach grown in greenhouses. (OC- organic compost, OC + AS - organic compost +75 kg of N ha−1 applied as ammonium sulfate, OC + AN- organic compost +75 kg N ha−1 applied as ammonium nitrate).