Sulfide toxicity reduces nutrients uptake of plants by reducing root respiration. It has an adverse effect on metabolism, when an excessive amount is taken up by rice plant.
Sulfide toxicity is not very common in rice. It is, however, associated with low-iron (Fe) soils.
It can occur in well drained sandy-soils, degraded paddy soils, poorly drained organic soils and acid sulfate soils.
How to identify (symptoms)
- interveinal chlorosis of emerging leaves
- Corse, sparse, dark brown to black root system
- Freshly uprooted rice hills often have poorly developed root system with many black roots, which are covered with a uniform and smooth orange-brown coating of Fe3+ oxides and hydroxides.
How to manage
- Plant tolerant varieties (by contacting your local agriculture office for an up-to date list of available varieties)
- Avoid continuous flooding and use intermittent irrigations in soils.
- Carry out dry tillage after the rice harvest to enhance Fe oxidation during the fellow period.
- Balance the use of fertilizer nutrients (NPK or NPK + lime) to avoid nutrient stress and to improve root oxidation power.
- Apply sufficient Potassium (K) fertilizer.
- Avoid using excessive amount of organic residues (manure, straw) in soils containing large amount of Fe and organic matter and in poorly drained soils.
