سیروان بابائی

Circium arvense (Creeping Thistle) is an increasing annual weed in winter crops such as wheat and barley in the semiarid region of Iran. Recent years this weed distributed under low impact tillage systems and current agricultural practice that has become popular. Seed dispersal in the soil profile under conventional tillage will change when reduced tillage is implemented, thus affecting on the micro environmental condition. A field experiment was carried out to determine the effect of seed burial depth and soil water regime on field's germination, obligate and innate dormancy, and seed decay in relation to burial time. In addition, the effect of burial depth on the seed germination and seedling emergence was studied under laboratory conditions. The experiment was performed using a completely randomized factorial design with three replicates .Treatments consisted of seeds buried at 2 and20 cm under two different fluctuating water regimes ,rain-fed (RAINF) and rain-fed plus irrigation (IRRIG),exhumed at different time intervals. Each treatment (combination of a given burial depth, soil water regime and time of burial) was applied to a mesh bag containing 50 seeds. Results showed that Field's germination of buried seed ranged from 45-60% for shallow depth (2 cm), and from 5-25% for greater depths (20 cm). Obligate dormancy was significantly higher among deeper burial seeds. The amount of innate dormant seeds was reduced to<10% after a year of burial. C. arvense seed banks can be classified as short-term persistent. Germination in the laboratory was unaffected by burial depth, while reducing in the seedling emergence was effectively described by a sigmoidal model. Results indicate that agricultural practices that accumulate C. arvense seeds near the soil surface enhance seedling recruitment