System for detecting fluorescent tracers in streamflow, A

December 1970.Includes bibliographical references (pages 180-186).Covers not scanned.Print version deaccessioned 2021.A system is developed capable of continuously monitoring the relative concentration of a fluorescent tracer in streamflow. Streamside instrumentation automatically registers stream-borne tracer concentrations as a function of time on a gelatin-coated film. The film is routed through a device which passes a continuous sample-aliquot diverted from the tracer-dosed stream over a small segment of the film. The "exposed" film is periodically gathered from stream sites and analyzed in a laboratory-based fluorometer. Utility of the system is studied for the gaging of streamflow to produce a hydrograph, to measure stream discharge instantaneously, and to determine time-of-stream-travel. Hydrographs resulting from 640 hours of gaging two Colorado mountain streams with the system are compared to those obtained from closely located sharp-crested weirs. The maximum instantaneous deviation between hydrographs reaches 10% and average absolute departure equals 1.8%, while algebraic departure averages +0.3%. The practicality of using this system to obtain time-of-stream travels is demonstrated for five Colorado mountain streams. A total of 62 traveling tracer-clouds are registered on gelatin-coated film, from which time-of-stream-travels are determined. Processes involved in the system and factors affecting its precision are investigated. Theoretical and experimental evidence strongly indicates that the bulk of tracer uptake by gelatin follows processes that are physical rather than chemical in nature. Stream temperature changes and duration of film-tracer contact are the two most important factors affecting precision of the system. Neither major factor caused any unsolvable problem when field operations were standardized. The system will have utility in operations where an expensive, temperature-sensitive fluorometer can not be stationed stream-side, and where the particular objectives of stream measurements do not justify the cost of conventional techniques, but where fair accuracy and continuous records of short to moderate duration are desired

Evaluating potential forages for suppressing foxtail barley and downy brome in saline pastures and hay fields

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Evaluating potential forages for suppressing foxtail barley and downy brome in saline pastures and hay fields

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Does seed size affect alfalfa establishment and productivity in saline seedbeds?

Non-Peer ReviewedLarge, medium and small seeds of Rangelander alfalfa, were sown in saline media in Canada’s Salt Tolerance Testing Lab. The emergence and survival data indicate that large-size seeds confer a degree of salinity tolerance to their emerging and developing seedlings. The large seeds emerged in numbers 10 and 23 % greater than the plants from medium and small seeds grown in 18 and 24 dS m-1 solutions, respectively. The seed-size advantage, evident in plant heights just 14 days after seeding, persisted into forage harvests which also showed increased biomass yields at all salinity levels at the first harvest cut. Although the seed-size yield advantages diminished with successive harvests, higher yields persisted at the 12 and 18 dS m-1 salinity treatments for the crops planted with large seeds

Pre-irrigation of a severely-saline soil with in-situ water to establish dryland forages

Non-Peer ReviewedAlfalfa serves as one of the most important forage plants in North America. It is also the recommended remedial crop for dryland salinity control. But, because of its limited salt tolerance, it does not establish satisfactorily in severely or moderately saline soils. A series of irrigations with the in-situ ground water located beneath a severely-saline site were delivered across seedbeds prepared within the same site prior to seeding ‘Beaver’ alfalfa (Medicago sativa) and ‘ AC Saltlander’ green wheatgrass (Elymus Hoffmannii). In this field study conducted in semiarid Saskatchewan, fall irrigations with 4.6 dS/m-water from a shallow, on-site, backhoe-dug well fitted with a solar-powered pump preceded spring seeding. Irrigation treatments ranged from zero to 2530 mm in total applied water. Plant emergence, spacing, height, cover, and forage yield of the alfalfa were significantly improved following pre-irrigation. Mean plant emergence increased from 20 to 79% for the alfalfa. The wheatgrass height and forage yield also improved significantly, but showed only an upward trend in emergence, spacing, height, and cover. The mean plant height in July increased from 90 to 159 mm for the wheatgrass and from 35 to 140 mm for the alfalfa. Based on linear regression of irrigated volume, every 119.3 mm of irrigated, in-situ water up to 2530 mm increased alfalfa forage yield by 10 g/m2

Does it pay to fertilize a mature forage stand on a severely saline field?

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Snow ridglng to increase soil water

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Effects of fallow replacement green manuring with annual legumes on soil water reserves

Non-Peer ReviewedLegume green manures are used in crop rotations to add organic matter, enhance N availability and to provide ground cover for soil conservation. In drought-prone regions like the Palliser Triangle, annual rather than perennial legumes could be used for fallow replacement green manuring in short rotations to avoid excessive depletion of soil water reserves. Results from a 6-year study of green manuring with 4 annual legumes in combination with snow trapping on a Brown loam at Swift Current were used to assess water use during legume growth, water use efficiency (WOE) of green manure production and amounts of soil water remaining for subsequent spring wheat. Each spring Black lentil, Tangier flatpea, Chickling vetch and Feedpea were seeded into wheat stubble with tall stubble trap strips along with continuous wheat and wheat-fallow plots. Legumes were incorporated in some and chemically desiccated in other plots as soon as they reached full bloom. Water use by the 4 legumes was generally related to DM production and did not differ from the amount used by wheat during the same vegetative growth period. Most of the water used was extracted from the 0- to 60-cm soil depth. On average, inoculated legumes used only 12% more water but produced much more DM than uninoculated legumes. Thus rhizobial seed inoculation and the enhanced N2-fixation elicited a doubling of the WUE by these green manures. Chickling vetch and feedpea were able to use water at a 20% greater efficiency than well fertilized spring wheat. Contrary to expectations, levels of soil water recharge between legume bloom and the following spring were always as high for incorporated as for desiccated green manures. At seeding time there was generally 20% less water under continuous wheat than in the fallow soil. In green manured soils, water reserves in spring did not differ between legume species and were usually 15% lower than in fallow plots with wheat trap strips. Wheat yields after green manures were affected primarily by weather and legume management but not by legume species. After incorporated green manures grain production was, on average, 12% and 17% greater than after conventional fallow or desiccated green manure, respectively. The presence of wheat strips in the fallow phase increased subsequent grain yields by an average 20%. We concluded that green manuring with annual legumes, when combined with snow trapping, offers a more bio-resource efficient and soil conserving alternative to conventional summer fallowing for wheat production within the Palliser Triangle