Type of property | Standard | |||||
Institute of standards and industrial research of Iran (weight based on the dry matter) | Standard products Washington ecology department | |||||
Acceptable range for Category A | Acceptable range for Category B | WHO standard (gr/100gr) | Gotas theory (gr/100gr) | Category A* | Category B* | |
Organic materials | At least 35% | At least 25% | 10 - 20 | 25 - 50 | At least 50 | At least 40 |
Organic carbon | At least 25% | At least 15% | - | 50 - 80 | - | - |
The amount of total nitrogen | 1.25% - 1.66% | 1% - 1.5% | 0.4% - 3.5% | 0.4% - 1.5% | At least 1% | At least 0.5% |
The ratio of carbon to nitrogen | 15 - 20 | 10 - 15 | - | - | Up to 15 | Up to 20 |
The amount of phosphorus in terms of P2O5 | 1% - 3.8% | 0.3% - 3.8% | 0.3 - 3.5 | 0.2 - 3.8 | - | - |
The amount of potassium in terms of K2O | 0.5% - 1.8% | 0.5% - 1.8% | 0.5 - 1.8 | 0.1 - 2.8 | - | - |
Sodium | - | - | - | - | - | - |
Arsenic (mg/kg) | - | - | - | - | - | - |
Lead (mg/kg) | - | - | 200 - 400 | - | - | - |
Cadmium (mg/kg) | - | - | 15 - 40 | - | - | - |
Mercury (mg/kg) | - | - | - | - | - | - |
Chromium (mg/kg) | - | - | - | - | - | - |
Conductivity (in 10% of dry matter) | Up to 8 ds/m | Up to 14 ds/m | - | - | <2 mmohs/cm | <3 mmohs/cm |
pH (in 10% of dry matter) | 6 - 8 | 6 - 8 | 6 - 8 | 6 - 9 | 5.5 - 6.5 | 5 - 8 |