Chemical properties of flooded soils
Rice is predominately grown under flooded conditions. This is unique for crop cultivation and has a big influence on the availability of nutrients.
The following chemical changes take place and influence nutrient availability.
Influence of flooding on nutrient availability
| Nutrient | Availability |
| P | Desorption of P held by Fe3 oxides |
| K | K Exchangable K is displaced from cation exchange sites into soil solution due to competition for mineral sites from Mn2+and Fe2. Flooding of soils containing K-fixing minerals may increase K fixation. |
| S | Reduction of SO42 to elemental S and sulfide |
| Zn |
Formation of Zn(OH)2 in acid soils and ZnS in sodic and calcareous soils. Formation of Zn-phosphates. |
| Mg | Tends to increase due to displacement of exchangable Mg2+ by Fe2+. |
| Ca | Tends to increase due to displacement of exchangable Ca2+ by Fe2+. |
| Fe | Fe3+ oxides are reduced to plant-available Fe2+ |
| Mn | Mn4+ oxides are reduced to plant-available Mn2+ |
| B | Availability decreases in acid soils and increases in alkaline soils |
Also Nitrogen is influenced by flooding. The picture below shows which N form is mainly present in flooded soil without fertilizer application.
