Egg incubation and larval rearing of navaga (Eleginus navaga Pall.), polar cod (Boreogadus saida lepechin) and arctic flounder (Liopsetta glacialis Pall.) in the laboratory

The embryonic and larval development of three White Sea cold-water fish species, rate of yolk sac absorption, age at first feeding and their survival and growth when fed different food organisms, were studied.Eggs were obtained from spawners in the Bay of Kandalaksha, White Sea, and incubated in troughs and aquaria at a mean temperature of 1.5 °C, slightly above that of the sea. The incubation period for polar cod eggs lasted 35 days, for arctic flounder, 42 days and for navaga eggs, 48 days. Emergent larvae were 5.5–6.0 mm long and began feeding at 2–4 °C, 5–6 days (navaga) and 12–14 days (polar cod) after hatching, when their yolk sac was still fairly large.They were fed day-old Artemia nauplii and zooplankton taken from the sea and consisting of Calanus and Pseudocalanus nauplii 400–600 μ in length.The period of establishing first feeding is the most critical for larvae.     

Calculation of hydraulic conductivities of horizons in some major soils in Wisconsin

Hydraulic conductivity between saturation and a tension of 100 cm water was calculated with moisture-retention data for nine soil horizons and compared with results from in situ measurements with the crust test. Agreement was good for sandy, apedal soil horizons with simple packing voids but only if matching factors were used. Results were unreliable in clayey, pedal soil horizons in which a few relatively large planar and tubular pores determine K in the measured tension range, whereas the greatest fraction of total porosity is composed of fine pores inside peds that hardly contribute to flow. Varying the number of pore classes (n) and the water-filled porosity at saturation made no significant difference in the calculations for the apedal soils, but drastically changed the shape of the calculated curves for the pedal soils. Matching factors based on K_sat measurement had to be used for all studied soil horizons, indicating that Marshall's pore-interaction model never predicted K_sat accurately.     

Rate of decomposition of organic matter in soil as influenced by repeated air drying-rewetting and repeated additions of organic material

Repeated air drying and rewetting of three soils followed by incubation at 20°C resulted in an increase in the rate of decomposition of a fraction of ¹⁴C labeled organic matter in the soils. The labeled organic matter originated from labeled glucose, cellulose and straw, respectively, metabolized in the soils during previous incubation periods ranging from 1.5 to 8 years.Air drying and rewetting every 30th day over an incubation period of 260–500 days caused an increase in the evolution of labeled CO₂ ranging from 16 to 121 per cent as compared to controls kept moist continuously. The effect of the treatment was least in the soil which had been incubated with the labeled material for the longest time.Additions of unlabeled, decomposable organic material also increased the rate of decomposition of the labeled organic matter. The evolution of labeled CO₂ during the 1st month of incubation after addition was in some cases 4–10 times larger than the evolution from the controls. During the continued incubation the evolution decreased almost to the level of the controls, indicating that the effect was related to the increased biological activity in the soils during decomposition of the added material.Three additions of organic material during the period of incubation resulted totally in an increase over the controls ranging from 36 to 146 per cent.     

The colonization of host-root and soil by rhizobia—II. strain differences in the species Rhizobium trifolii

The ability of four strains of Rhizobium trifolii to colonize host-root and soil was compared at 5-day intervals up to 70 days from sowing into a field soil. Strain differences in colonizing ability were demonstrated, with one strain (TA1) consistently inferior to the other three which comprised another introduced strain (UNZ29) and two locally isolated strains.