Sulphide injury in rice
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Healthy rice plants release sufficient quantities of oxygen to inactivate the accumulated sulphide in the rhizosphere.
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YOUNG RICE saplings grown during the monsoon (samba season) in soils with high clay content and poor drainage are susceptible to sulphide injury.
The affected saplings exhibit stunted growth and reduced tillering. The roots of freshly pulled out plants are black in colour having a deposition of ferrous sulphide, whereas roots of the healthy plants are covered with a uniform and smooth light brown coating of ferric oxides and hydroxides.
Other manifestations like appearance of small brown spots on the lower leaves and leaf blades which turn purplish-brown are also noticed.
Soil texture
Accumulation of chemically reduced ferrous sulphide also imparts a black tinge to the soil and emanation of the accumulated gas as small air bubbles can be seen when the soil is tilled.
Young plants are highly susceptible to this injury due to poor root oxidizing power.
On the contrary, healthy rice plants could release sufficient quantity of oxygen to inactivate the accumulated sulphide in the rhizosphere.
Efficient drainage
Continuous flooding of fields must be avoided in general and the practice of intermittent irrigation can expel the accumulated hydrogen sulphide gas, particularly in heavy soils lacking proper drainage
For severe sulphide injury either the flooded soil needs to be drained and allowed to dry for 7-10 days or allowed for intensive drying for 1-2 days to form hairline cracks which will provide oxygen supply to the roots.
Management practices
— Placing a thin film of water, for improving oxidising capacity of the roots of the plants.
— Application of urea at 55 kilogram a hectare and muriate potash at 42 kilogram a hectare and nitrogen fertilizer application. Fields prone to this infestation should be ploughed and exposed to drying to increase the oxidation of sulphide and ferrous compounds.
K. Natarajan, P. Stalin
& B. Chandrasekaran
TRRI , Aduthurai
Tamil Nadu
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