Preliminary study of management techniques through dormancy-breaking on weedy rice.

Abstract

Rice (Oryza sativa L.) is the staple food that is widely grown as a wetland crop in Sri Lanka.Weedy rice (Oryza sativa f. spontanea) is rated as one of the four most noxious weeds infesting rice fields worldwide. Seed dormancy is an evolutionary adaptation or a condition which seeds are prevented from germinating even under favourable environmental conditions. The extended dormancy is one of the survival mechanisms of weedy rice. Due to the shattering effect the time gap between after the maturity to on the date of the land preparation weedy rice seeds are laid on the top layers of the soil. The fallen seeds are mix with the soil and deposit in different depths of the soil during the land preparation process. Therefore, the objective of this study is to break the dormancy of weedy rice seeds which are deposited on ground layers of paddy fields and allowing to germinate on site. After the germination adaptation of control package recommended by the Department of Agriculture can be done. Dormancy breaking chemicals were tested for the effectiveness under the laboratory conditions. Weedy rice seeds were collected from three weedy rice infested fields (Dehiduwa, Naiduwa and Yatagala) from Galle District. Sodium Nitrite 1000ppm, Sodium nitrite 3000ppm, N propranol 2 ppm, N propanol 6 ppm, N Propanol 10 ppm, Propionic Acid 5ppm, and Propionic Acid 10 ppm were applied as seed treatments for the composite samples of weedy rice prepared and allow to germinate 100 seeds with three replicates in petri dish by keeping six days as it is. On the seventh day wash off the seed sample by distilled water and germination percentage was recorded. The procedure was repeated for eight weeks with three replicates by keeping one week interval. Sodium Nitrite 1000ppm was recorded significantly highest germination percentage compared with the control and the other chemicals in separately in three locations (Naiduwa,Dehiduwa and Yatagala) by the repeated measures analysis of variance (mixed procedure with time).Therefore Sodium Nitrite 1000ppm can be effectively used to break the dormancy of weedy rice in laboratory conditions. Further evaluation of chemicals and hormones in field level their residual effects before the use of techniques.