Water Retention, Bulk Density, Particle Size, and Thermal and Hydraulic Conductivity of Arable Soils in Interior Alaska

The relative proportion of liquid, gas, and solid as constituents of soil depends on factors such as climate, biological activity, and management practices. Therefore, the physical state of soil is a dynamic process, changing with time and position in the profile. Temperature, thermal and hydraulic conductivity, density, and water content are some quantitative properties characterizing the physical state of soil. These properties are important in describing soil processes such as water and heat flow, movement of chemicals, biological activity, and erosion. Water in the soil is subject to a number of forces resulting from the attraction of the soil matrix for water and presence of solutes and gravity. The energy status of water-the sum of these forces-is termed water potential. Processes such as evaporation and plant water uptake are governed by the gradient in water potential in the soil and across the root-soil interface, respectively. The term water potential is more descriptive of the soil water status than water content as movement of water is in response to differences in water potential

Migration of Water During Winter in West Central Minnesota Soils

Soil freezing influences the amount and quality of our water resources, yet, little is known concerning the impacts of soil texture and water content before freezing on water migration in frozen soils. Columns of Hamerly clay loam and Sioux loam at 3 initial water contents were subjected to the vagaries of the field environment at Morris, Minnesota during the winter of 1993-1994 and then sectioned to determine changes in soil water content. Redistribution of water in the frozen soil layer became more apparent with an increase in initial water content. Little movement of water occurred at the lowest initial water content of 0.21 g g-1 (45% pore saturation). Soil water redistribution was more pronounced for the. Sioux loam, but only at the highest initial water content of 0.38 g g-1 (8QO;O pore saturation). Upward water movement appeared greatest when the rate of descent of the freezing front was slowest. Initial water content had a larger effect on water movement in frozen soil profiles than soil texture. Therefore, soil water content at the time of freeze-up in the fall will determine, to a large extent, the rate of water (and consequently solute) movement in soil profiles during winter

Dissipation of Bromide and Metribuzin Affected by Tillage and Crop Residue Management in Subarctic Alaska

Prudent use of agricultural fertilizers and herbicides is paramount for sustaining or improving surface and ground water quality in Subarctic regions, but little information is available that documents the loss of chemicals from agricultural lands in the Subarctic. This study aimed to ascertain more clearly how time of application and land management practices affect the loss of bromide and metribuzin in a Subarctic soil. Potassium bromide (KBr), a surrogate for nitrate, and metribuzin, commonly used to control broadleaf weeds, were applied in the autumn of 1996 and the spring of 1997 to a silt loam that had been subjected to conventional tillage (CT), minimum tillage (disk once [DO]), and no tillage (NT) since 1983. Superimposed on the tillage treatments were the removal or retention of barley (Hordeum vulgare L.) stubble and loose straw. Loss of these chemicals was ascertained by sampling the soil profile at the time of heading of barley, before freeze-up of the soil in autumn, and after spring thaw until September 1998. Tillage and residue treatments did not influence the recovery of autumn-applied or spring-applied Br. However, recovery of Br diminished with time: about 30% of the Br applied in autumn and 45% of that applied in spring remained in the soil profile by September 1998. Tillage, but not residue, treatments influenced the recovery of metribuzin. Recovery of metribuzin at the termination of this study was 6% or more in NT soil and 2% or less in CT and DO soil; greater recovery in NT soil was presumably a result of slower degradation in NT than in CT and DO. This study suggests that bromide (and thus nitrate) and metribuzin are more prone to leaching when applied in autumn and that tillage practices affect retention of metribuzin, but not nitrate, in the soil of Subarctic Alaska.Une utilisation prudente des engrais et des herbicides est cruciale au maintien ou à l’amélioration de la qualité de l’eau de surface et de l’eau souterraine dans les régions subarctiques, mais il existe peu de documentation sur la déperdition des produits chimiques dans le sol des terres agricoles du Subarctique. Cette étude vise à établir avec plus de précision la façon dont le moment de l’application et les pratiques de gestion des terres affectent la déperdition du bromure et de la métribuzine dans un sol subarctique. Le bromure de potassium (KBr), un substitut du nitrate, et la métribuzine, couramment utilisée pour lutter contre les dicotylédones, ont été appliqués en automne 1996 et au printemps 1997 sur un loam limoneux qui avait subi un travail du sol classique (TC), un travail minimum (un seul passage du cultivateur à disque [TM]) et aucun travail (AT) depuis 1983. On a ajouté au travail du sol le déchaumage de l’orge (Hordeum vulgare L.) ou le maintien du chaume et de la paille. On a vérifié la déperdition de ces produits chimiques jusqu’en septembre 1998 en analysant le profil pédologique au moment de l’épiaison de l’orge, avant que le sol gèle à l’automne et après le dégel printanier. Le travail du sol et le traitement des résidus n’ont pas influencé la récupération du Br appliqué en automne ou au printemps. La récupération du Br a cependant diminué avec le temps: en septembre 1998, environ 30 % du Br appliqué à l’automne et 45 % de celui appliqué au printemps persistaient dans le profil pédologique. Le travail du sol, mais pas le traitement des résidus, influençait la récupération de la métribuzine. À la fin de l’étude, la récupération de la métribuzine était de 6 % ou plus dans le sol AT, et de 2 % ou moins dans les sols TC et TM; une récupération plus importante dans le sol AT résultait probablement d’une dégradation plus lente dans le AT que dans le TC et le TM. Cette étude suggère que le bromure (et, par conséquent, le nitrate) et la métribuzine sont plus sujets au lessivage quand ils sont appliqués en automne, et que les pratiques de travail du sol affectent la rétention de la métribuzine, mais pas celle du nitrate, dans le sol de l’Alaska subarctique

Frozen Soils: A Perspective On Past And Future Research For Promoting Sustainable Agricultural Systems

Frozen soils impact many industries which rely· on soil, water, and .air resources in developing and manufacturing products. Most noteworthy is the agricultural industry in the northern United States where soils, which sustain food and fiber production, are subjected to frequent freezing and thawing. Soil freezing and thawing influences soil erodibility, surface and ground water quality, air quality, and biological activity. Many strides toward understanding frozen soil processes and managing lands to minimize the adverse effects of freezing and thawing have been made over the last two decades. Yet, further efforts to identify frozen soil processes which influence wind and water erosion, soil faunal adaptation, soil quality, movement of agricultural chemicals,· and rural and urban water supplies will aid industry and society in meeting future needs for food and water

Frost Depth

Freezing and thawing of soil is a common occurrence throughout the world. Indeed, approximately 50% of the Earth landmass is frozen at some time during the annual cycle, with 20% of the land underlain by permafrost (Sharratt et al., 1997). Seasonal freezing of soils with sparse vegetation and snow cover can occur to depths of 3.5 m (Kennedy & Sharratt, 1997; Shul’gin, 1965) while seasonal frost has been found to penetrate to depths of \u3e6 m below paved runways (Carlson & Kersten, 1953). The extensiveness of soil freezing and the impact of freezing and thawing on the physical, chemical, and biological properties of soils demand a thorough assessment as to the timing and depth to which freezing occurs in soil

Freezing and Thawing of Agricultural Soils: Implications for Soil, Water, and Air Quality

Most agricultural lands in the USA are subject to subfreezing temperatures. Soil freezing and thawing affects both biotic and abiotic interactions and processes which vary with weather, soil type, land management, and topography. Soil fauna generally undergo physiological changes or rely on locomotion as a means of adapting to frozen soils. Managing faunal populations using soil management may be achievable with a better understanding of winter ecological processes. Many of the thermal, hydraulic, mechanical, and physical properties of soils are altered by freezing and thawing. Soil erosion may be accentuated by soil freezing and thawing as a result of changes in aggregate stability and shear strength. Soil processes such as heat, water, solute, and gas flux are affected by the freezing process, although simulation of solute and gas flux in frozen soils is not well documented. Solute and gas flux affect water and air quality owing to the loss of chemicals to surface and ground water systems and gaseous emissions to the atmosphere, respectively. Information about biotic and abiotic characteristics of frozen soils, presented at a national workshop in March 1994 in Minnesota, aids in the development of sound management strategies for agricultural lands to preserve our soil, water, and air resource