Effects of soil water status and depth of burial on dormancy changes of Polygonum aviculare L. seeds

DIEGO BATLLA; ROBERTO LUIS BENECH-ARNOLD

Foz de Iguazú, Brasil

Congreso; III Intenational Weed Science Congress; 2000

International Weed Science Society

Effects of soil water status and depth of burial on dormancy changes of Polygonum aviculare L. seeds DIEGO BATLLA* and ROBERTO L. BENECH-ARNOLD Department of Crop Production, Faculty of Agronomy, University of Buenos Aires, Av. San Martín 4453 (1417), Buenos Aires, Argentina; batlla@mail.agro.uba.ar ABSTRACT- Although there is much information about the role of temperature on annual changes of dormancy of buried weed seeds, little is known about how seed dormancy can be modified by soil water status and depth of burial. In order to highlight these questions, seeds of Polygonum aviculare contained in nylon mesh bags, were buried in the field at two depths (5 and 15 cm) and subjected to three different hydric conditions: irrigated, dry and rainfed. At regular intervals, seeds were exhumed and the population dormancy level was assessed through: i) the range of temperatures suitable for germination and ii) sensitivity to light. Data from successive exhumations, showed that seeds entered secondary dormancy soon after burial, but to a different extent depending on the water regime given to the seeds in the field and on the depth of burial. For example, seeds buried at 5 cm in rainfed plots were able to germinate in a wider thermal range than seeds buried under other conditions, showing that those seeds entered secondary dormancy at a lower rate. On the other hand, depth of burial played an important role in determining changes in light sensitivity; seven months after burial seeds buried at 15 cm were more sensitive to light than seeds exhumed from 5 cm; only when the seeds were held at high soil water content (irrigation), could seeds placed at 5 cm respond to light as did seeds buried at 15 cm. These results suggest that the effect of depth on seed dormancy could be mediated by the different water conditions that prevail at the different depths. Overall, these results, show that soil water status and depth of burial play an important role in determining changes in the dormancy level of weed seed banks. KEYWORDS: dormancy, Polygonum aviculare, soil water status, depth of burial and light sensitivity.