Iron Toxicity in Rice

The plant shown below is exhibiting symptoms that could be the result of several things.  The rust colored leaves can be associated with zinc deficiency (bronzing), localized decline or as in this case iron toxicity.

The next photograph shows heavy iron accumulation on debris under the water, a common site near water wells throughout much of the state.

One possible solution is to aerate the water as it enters the field as is done when pumping well water onto crawfish ponds.  Even though the water looks crystal clear it has low oxygen levels and the iron in it is in a reduced form.  According to Dr. Harrell reduced iron is more mobile; therefore it is likely to be taken up rapidly by the plants.  If oxygen is added to the water much of the iron is converted from reduced to oxidized form which is less toxic and less likely to be absorbed by the plants.

There are indications that this could solve the problem because the problem decreases as it gets farther from the inlet.  In many cases I have seen small paddies deliberately set up near the inlet to serve as a sacrificial area.  Once water moves through this paddy the others are not affected or at least not as severely.

Keep in mind we have not conducted research to support this recommendation; we are relying on past experience and some knowledge of the behavior of iron.

The symptoms are very similar to Localized Decline because Localized Decline is also associated with high levels of iron and aluminum uptake by rice plants.  The difference is that the exact reason this is happening is still undetermined.  We do know high levels of zinc, especially where soil pH is high will correct the problem in some cases.

Foliar symptoms of iron toxicity in rice

Foliar symptoms of iron toxicity in rice

Iron deposits in rice field

Iron deposits in rice field

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