The effect of fresh water storage on the germination of certain weed seeds. I. White top, Russian knapweeds, Canada thistle, morningglory, and poverty weed.

摘要: ATER, especially water used for irrigation, has been adjudged vIe many years an important agent in the dissemination of weed seeds. Egginton and Robbins (7) found a total 81 different species weeds 156 seed catches from three ditches during 1918 1919 determined that number seeds passing given point on ditch which averaged 12 feet width period 24 hours may reach several millions. Hope (11) analyzed considerable irrigation channels 1924 1925. He computed 1,674,030 13 occurred surface to depth 1.57 inches one 10-foot passed 24-hour September 2, Further computations illustrated flow would amount deposition 170,800 per acre land 6-inch irrigation. The latter were based assumption distributed uniformly over cross section at catch. extent are carried farm lands by depends, part, degree buoyancy such secured data showed differ readiness with they sink or float. is influenced somewhat condition manner alight upon it. Some float days no matter how strike it agitated; some if laid carefully not disturbed, but readily agitated, almost immediately sufficient force. Bruns (4) dropped 100 each morning glory (Convolvulus arvensis L.), Russian knapweed (Centaurea repens white top (Cardaria draba (L.), Desv. var. (Schrenk) 0. E. Shulz), Canada thistle (Cirsium arvense poverty (Iva axillaris Pursh.) into separate 11/8-inch columns still 48 deep. Agitation break tension was supplied vigorous stirring glass rod short periods day. This test indicated relatively buoyant might be transported distances water.