Biology and ecology of weedy rice in direct seeded rice

Nimmy Jose Leenakumari S,Dhanya Das, C T Abraham, Joseph Job

Abstract


Weedy rice is a complex of Oryza morphotypes widely distributed in commercial rice fields. Indian weedy rice has been reported to be Oryza sativaf.sp. spontanea, belonging to indica group.Heavy infestation of weedy rice and subsequent reduction in crop yield (60-80%) in rice fields of of Kerala state during recent years have forced farmers to abandon rice cultivation. Morphological similarity with cultivated rice, variable seed dormancy, early seed shattering, staggered germination and its high competitiveness make hand weeding incomplete and ineffective. Survey in the infested areas revealed the presence of weedy rice morphotypes with variation in morphological and physiological characters. The study revealed the presence of hull induced dormancy and staggered germination in weedy rice. Knowledge on the biology of weedy rice can help in formulating suitable package for integrated management of weedy rice. As no single method of control will be effective for managing weedy rice, integrating techniques like stale seed bed with repeated ploughing, pre sowing surface application of herbicides, direct contact application of herbicidesusing specially designed wick applicator, use of certified seeds, water management etc., depending on the ecological situation can reduce soil seed bank and infestation in the rice fields.

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