The effects of two water regimes: Continuous flooding and flooding with soil drying on iron toxicity
to rice in an acid sulfate soil was studied by continuously growing 7 crops of IR-32 rice in pots under
the two water treatments. There was no plant growth upto the second crop under both water
treatments due to iron toxicity. But there was good growth of rice under the continuous water regime
from third cropping onwards, however, there was no growth of rice in the flooding with soil drying
treatment even upto the seventh crop due to iron toxicity.
The results of the study bring out that keeping an acid sulfate soil flooded for a few weeks
and then planting rice when iron in soil solution has dropped below toxicity level may be a possible
management practice for lowland rice culture on such soils. Drying and reflooding an acid
sulfate soil on the other hand aggravates soil acidity and keeps iron in solution in high amounts
to be toxic to rice plant