THE DORMANCY BEHAVIOR OF AVENA FATUA L. IN CULTIVATED SOIL

Abstract

Recovery of dormant, non-dormant and dead wild oat seeds and seedling emergence from naturally-infested Regina heavy clay soil was used as a measure of viability during 5 years of consecutive summerfallow subsequent to 13 years of continuous cropping.Percentage viability and dormancy corresponded closely throughout the first summerfallow period. By season’s end 33 per cent of the seeds were viable but mostly dormant. It was concluded that persistence was due primarily to seed dormancy and not lack of germinative conditions.Numerous seedlings emerged the following spring until early June when viability averaged 4 per cent. The potential value of delayed seeding methods of control was indicated clearly at this time. Persistence of seeds in the soil in the second and two succeeding summerfallow years was attributed largely to primary seed dormancy. Lack of moisture and oxygen contributed temporarily. There was little or no evidence of secondary dormancy induction under field conditions. Neither moisture nor oxygen supply appeared to seriously reduce total emergence in adjoining cropland. It was concluded that wild oats could be "grown out" equally well in a 2-year rotation of alternate crop and summerfallow as by means of 2 years of consecutive summerfallow if re-infestation was prevented during the crop year.Inhibition of germination of surface seeds, presumably by light, did not markedly prolong persistence of viable seeds in the soil. No viable seeds were found on the surface after June of the third summerfallow year.Results indicated that a minimum of 5 years is needed to elminate wild oats from heavy clay soils under cultivation.