Arctic Investigations by the Fisheries Research Board of Canada, 1956-57

... In 1956 fisheries studies were concentrated in the Mackenzie Delta region between Herschel Island and Tuktoyaktuk, where fishes are relatively varied and abundant. ... In addition to substantial beluga and ringed seal collections which were made for the mammal investigations, about 11,000 fish were sampled in all. ... a preliminary survey of fish stocks in Pelly and Garry lakes of the Back River system was undertaken .... The lakes, which are shallow (20-30 feet), were found to support sufficient stocks of whitefishes and lake trout to permit organized subsistence fishing should this be necessary. ... In 1957 one party carried out fisheries studies up the Mackenzie River from Aklavik to Fort Norman, and another surveyed fish stocks at Coppermine, N.W.T. An intensive study was made of the char run in Rowley River on Rowley Island, Foxe Basin by the M .V. Calanus and in northern Hudson Bay by whaleboat and by peterhead from Coral Harbour. Forty-five walrus were tagged in the latter area, and 20 were examined in detail. In Foxe Basin 60 walrus and 220 seals were sampled. The reproductive cycle, ages at maturity, and life expectancy have to a large extent been clarified by work on aging from growth layers in the cementum of molar teeth and in tusk development. ... In 1956 and 1957, a continued increase in the fishery for pilot whales in Newfoundland (1956 catch, about 10,000) led to emphasis on population studies. Investigations were begun as well on minke whales or lesser rorquals, with a small fishery at Dildo, Newfoundland as the source of material. ... During a 12-month period beginning in September 1955, collecting of plankton, benthos and hydrographic samples was carried out in northern Foxe Basin from the M.V. Calanus, based at Igloolik. Biological samples included net plankton, microplankton, bottom fauna and intertidal collections. Hydrographic sections were run across Fury and Hecla Strait, and between Jens Munk and Koch, Koch and Rowley, Koch and Baffin, Baffin and Bray, and Bray and Rowley Islands. Additional stations were occupied and water temperature, salinity, oxygen and phosphate values were determined. It thus has been possible to follow through a complete yearly cycle of hydrography and productivity in Foxe Basin. ..

An Inexpensive Method of Determining Plant Moisture Stress Using Freezing Point Depression

The measurement of freezing point depression as a method of determining osmotic potentials in solutions has been used for some time. Recently, this same principle has been applied to the determination of moisture stress in plant leaves. The advent of efficient solid state Peltier cooling units has made possible the construction of portable field freezing-point meters of relatively low cost and acceptable accuracy (1)

Irrigation Decisions Simplified with Electronics and Soil Water Sensors

Two simple, inexpensive systems use electrical resistance measurements to provide useful, immediate information to assist decisions made on irrigation water application. in one system a microprocessor-based circuit coupled to a programmable calculator provides an on-site estimate of the time until the next irrigation will be required, based on field data and an operator-supplied parameter. The second system simply signals the arrival of the wetting front at any location in the soil by giving a visual indication, such as raising a mechanical flag. The microprocessor-based circuit measures and stores the resistance of four gypsum blocks once a day. The program in the portable calculator accesses this information and uses it to extrapolate the soil drying rate to predict the number of days until the next irrigation. By restricting the microprocessor circuit to data acquisition only and putting all number-handling routines into the calculator program, the cost and complexity of the microprocessor circuit is minimized, whereas maximizing the programming flexibility. This makes it feasible to install a number of these devices at different locations, all serviced by the same portable calculator. The water infiltration circuit intermittently scans eight sets of stainless steel electrodes to locate the soil wetting front during irrigation. When the resistance across the electrodes decreases, sig- 'sling the arrival of the front, the circuit trips a spring-loaded Bag. This provides a visible sign that the wetting front has reached that point in the soil. The equipment worked well. When irrigation was required in six or fewer days, the microprocessor/calculator system made correct predictions 85% of the time. An example of how easily any irrigation scheduling method may be converted to the microprocessor/calculator system is presented

A Photoelectric Seed Counter

Small scale yield studies, germination tests, controlled plantings, and packaging often require the counting of large numbers of seeds. The system described in this paper uses a photosensitive detector and a vacuum pickup to count individual seeds and gives a direct digital readout. The count rate is limited only by how quickly the seeds can be fed through the counting tube without clogging it or having them touch each other. This greatly speeds seed counting, eliminates operator error, and reduces operator fatigue. With the addition of a relatively simple predetermining circuit, a fixed number of seeds may be counted and a control function can be exercised. This capability is immediately applicable to packaging or repetitious batching of seeds. Zero error for any given number of seeds is attainable if the seeds are fed through the count tube carefully because of the completely digital nature of the circuit

Electronic Single Station Irrigation Timer/Controller

Automation is being used increasingly to improve farm water application efficiency and to reduce labor requirements. For many years, farmers have wanted and needed time-controlled devices and structures to change their irrigation sets automatically, particularly when it is inconvenient for them to make the change, such as at night. Such equipment has not been available commercially

Water sensor feedback control system for surface irrigation

A water sensor feedback control system was developed to control semiautomatic irrigation of basins and borders. When water reaches a sensor at a downfield irrigation cutoff point, a signal to terminate irrigation is sent via wire or infrared (IR) telemetry to a station controller or receiver at the upper end of the field. The sensor uses a monostable interface to strengthen the signal for wire transmission, and prevents continuous IR transmission during the time the sensor is immersed or remains wet. The water sensor controller, powered by a 12-V battery, uses a silicon controlled rectifier (SCR) triggered by the feedback signal to discharge a capacitor through an electric solenoid. The energized solenoid actuates a gate release or valve to terminate irrigation of one field segment and begin irrigation of another. The water sensor system was tested in a level basin irrigation system. A sensor costs approximately U.S. $30, while single and dual station controllers cost about$65 to 80. Both can be portable to minimize the number of units required

Plant Water Potential Gradients Measured in the Field by Freezing Point

A portable freezing point meter was used in the field to measure the water potential gradients in sunflower (Helianthus annuus), beans (Phaseolus vulgaris), corn (Zea mays), wheat (Tritium aestivum), pumpkin (Cucurbita pepo), potato (Solanam tuberosum), alfalfa (Medicago sativa), and sugarbeets (Beta vulgaris). The measurements were made between daybreak and sunrise, and again during the middle of the afternoon on days when the potential evapotranspiration varied between 6.5 and 8.0 mm of water. The gradients varied from a maximum of 0.2 bar per cm in a wheat, down to an undetectable value for pumpkin. Although most of the soil in the root zone was kept at potentials above –1 bar, the bulk of the root tissue had water potentials of –5 to –10 bars. Differences in water potential between shaded and unshaded leaves, and between leaf tissue and guttation fluid suggested a similar drop of several bars between xylem elements and the surrounding leaf tissue in some plant species. The implications of such drops are discussed with respect to plant water transport equations and pressure cell potential measurements

A radio-controlled trencher for accurate installation of shallow ditches and pipelines

An inexpensive, radio-controlled, rotary trencher was developed for installing partially-buried surface pipes on an accurate grade. The method was developed for use with the Cablegation automated surface irrigation system and other gated pipe systems. The trencher is mounted on a farm tractor and offset to cut the trench behind the rear tractor wheel. The grade is remotely controlled by an operator sighting through an ordinary surveying instrument and adjusting the cutting depth via a radio control. Tests have shown that the trench grade can be controlled to an accuracy of ±10 mm (0.03 ft). The trencher and control system costs about $1500, not including the surveying instrument

Accumulation of Mercury Vapor in Soils Laboratories

The rate of accumulation of mercury vapor in a closed room was determined as a function of surface area of the exposed mercury, ambient temperature, and air flow. The rate of mercury vapor accumulation was much higher than suspected by many soil scientists. For example, in a 3- by 3- by 2-m constant temperature room, 250 cm² of mercury surface produced toxic levels of mercury vapor within 13 minutes. Water or oil covering the surface of the mercury was a highly effective means of suppressing vaporization. The standard decontamination treatment with sulfur proved effective, but only after complete amalgamation occurred