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When surface soils are dry, O2and N2are adsorbed on the external mineral surfaces. In the process of wetting the soil, water molecules displace the adsorbed O2and N2molecules to the gas phase where they can be measured, as was done in this study. These gases, released from the adsorbed phase, join entrapped air in the gaseous phase as the primary factor disintegrating aggregates when soils are wet quickly. Adsorption of N2and O2occurs on surface soils during hot dry afternoons as the water molecules leave the surface. During cool nights, relative humidities commonly rise above 50%, allowing more strongly adsorbed H2O molecules to displace adsorbed O2and N2. Release of this adsorbed N2and O2causes aggregates wetted by immersion during hot afternoons to be less stable than aggregates of the same soil wetted in the morning.

Cohesion increased for several months after disruption in moist soils. Rate at which cohesion increased was slower in airdry soil, but continued for years. Moduli of rupture of soils also increased with time. Effects of water content on the rate at which cohesion increases are compatible with an explanation of the bonding mechanism in terms of slightly soluble components diffusing to and cementing points of contact between particles. Cohesional forces due to water are estimated and found to be large enough to provide a major portion of the cohesion measured in soils. These estimates are supported by decreased cohesion of a silty soil when dried. However, cohesion of soils with larger amounts of clay generally increases when they are dried, indicating that other bonding mechanisms predominate.

Dissolution rates of gypsum were measured in water flowing through beds of gypsum fragments as affected by fragment size, solution velocity and initial concentrations of Ca2+, SO42‐and CO32‐in the flowing water. Equations were derived to describe the rates of dissolution, and a dissolution coefficient was defined which is a function of fragment size and solution velocity. Rates of dissolution are high enough to distribute quantities of gypsum, which are within economic reach of the farmer, on farm lands via the irrigation water. Sample calculations are made to show how these data may be used to design watercourse cross sections for applying given levels of gypsum to the flowing water.

Air‐dried soils were wetted by flooding, immersion, slow immersion and capillary action; these actions resulted in successively slower rates of wetting. In general, slower rates of wetting left larger portions of the soil volume in large size pores. Slow capillary wetting of a weakly structured soil allowed retention of more large size pore space than was observed in a well structured soil that was wet rapidly. Modulus of rupture was determined on dried soils which had previously been wet by rapid immersion, capillary action, and capillary action followed by immersion. Breaking strength was much greater when those soils had been wet by rapid immersion than when wet slowly by capillary action. Immersion following capillary wetting resulted in soils with intermediate breaking strengths. A preliminary study on corn (Zea maysL.) seedling emergence showed that the range of soil strengths resulting from these irrigation methods on a weakly structured soil was sufficient to give < 50% emergence (flooding) up to essentially 100% (capillary wetting).

Irrigation in furrows and placement of fertilizer in bands in ridges was evaluated as a means for allowing overirrigation to bypass nitrate and reduce leaching losses. In a loamy sand, placement of band 0 to 5 cm higher than the surface of water in the furrow allowed over 120 cm of overirrigation before the salt began to leave the root zone. In the clay loam a similar delay of nitrate removal was not achieved until the band was 10 cm higher than the water surface. This difference appeared to be associated with a perched water table that developed in the “cultivated” layer of the clay loam soil due to higher hydraulic conductivity in cultivated than in the lower soil. Downward movement of relatively concentrated salt solution near the band, due to its greater density, was a factor that allowed fertilizer bands at lower levels to enter the mainstream of the leaching water. Leaching of fertilizer from a soil can be delayed by placing it in ridges and irrigating in furrows rather than broadcasting fertilizer followed by flood irrigation. The practical significance of nitrate staying in the root zone longer as a function of such water and fertilizer management should be tested in the field.

Mouse erythroleukemia (MEL) cells provide a useful model system to examine the regulation of globin gene expression. MEL cells ordinarily do not express globin genes, but in the presence of inducers, such as dimethyl sulfoxide or hexamethylene bisacetamide, they mimic erythroid differentiation. We have developed a cell-free transcription system from uninduced MEL cells to determine the requirements for mRNA synthesis. The MEL system directs accurate transcription of adenovirus type 2 major late DNA and mouse betamaj-globin with an efficiency comparable to those of HeLa and KB cell extracts. Using the procedure of Matsui et al. (T. Matsui, J. Segall, P.A. Weil, and R.G. Roeder, J. Biol. Chem. 255:11992-11996, 1980), we have isolated three active fractions from both MEL and HeLa cell extracts which are required for accurate transcription and have shown that equivalent fractions from MEL and HeLa cell extracts are interchangeable. Our findings suggest that the components required for initiation of transcription are similar in different cell types, at least to the extent that they can be assayed in these in vitro systems.

This study was developed to determine whether there are substantial annual changes in soil cohesion and to identify major factors causing those changes. Aggregate stability was measured throughout the year on soils in Utah and Idaho using wet sieving techniques. Stability generally increased during spring and summer months. Major decreases of cohesion, found when minimum daily air temperatures fell to or below 0 °C during winter and early spring months, were attributed to pressures and associated shearing forces caused by freezing at high water contents. Equivalent disruption occurred when confined soils were frozen in controlled laboratory studies. Disruption also increased as water content at the time of freezing increased for all soils studied. Disruption of soil by rototilling and compaction significantly decreased soil cohesion.

Soils were dispersed and separated into sand, silt, and clay fractions that were reconstituted to give mixtures of each soil with 5 to 40% clay. In the range from 0 to 35% clay, higher clay contents resulted in greater stability. Rate of cohesion recovery was over 10 times as fast at 90°C as it was at 23°C, showing that the processes involved are physical‐chemical rather than biological. Maximum rates of cohesion recovery occurred at moderate soil water tensions, probably because some tension is needed to pull the particles into direct contact, but a continuous water phase is also essential to allow diffusion of bonding agents to the contact points. Since diffusion rates in water increase 300%, while rate of cohesion recovery increased 1000% when temperature was raised from 23 to 90°C, other factors, such as higher solubilities at higher temperatures of compounds contributing bonding ions to the solution, probably play a role in the rate of cohesion recovery. Recovery of cohesion was more rapid in the soil with organic C contents of 0.004 kg/kg than in the soil with 0.012 kg/kg. When the organic matter was removed with H2O2from the soil with 0.012 kg C/kg, its rate of cohesion recovery increased. Rate of cohesion recovery of this high organic matter soil was also increased by aging it at 0.1 kg H2O/kg soil compared to 0.2 kg/kg. A possible explanation is that organic coatings, tending to prevent direct contact and bonding of adjacent projections of mineral surfaces, are forced away from contact points by extremely strong forces that pull the adjacent minerals together when soil water tensions are high. When the higher organic matter soil had been consolidated by air‐drying and rehydrated, its rate of cohesion recovery was just as rapid as that of the soil with low organic matter.

Infiltration rates, volume reduction, and bulk densities of soils were determined on soils as a function of compacting pressures and water content at the time of compaction. Maximum compaction generally occurred when the soils were packed at water contents near field capacity. When compacting loads were < 1 kg/cm2the minimum bulk densities occurred when soils had water contents of about one half field capacity, indicating that surface tension of water films in the soils plays a major role in cohesiveness and stabilization against compaction under these conditions. Compacting loads of 3.46 kg/cm2, at field capacity on sandy loams and finer textured soils, reduced infiltration rates to < 0.1% of values obtained after these soils had been compacted when they were air dry. In a loamy sand soil this reduction was to about 1%. The low infiltration rates following compaction were increased by wetting and drying, although several cycles of wetting and drying did not raise the infiltration rate to the level observed before packing. Freezing and thawing cycles also increased the infiltration rates of previously compacted soils. Most of the change took place in the first freezing and thawing cycle. The large changes in infiltration rates using achievable levels of compaction at the “optimum” water contents indicate that compaction can play a major role in the management of water in ditches, reservoirs, furrows, and watersheds.

Evesboro loamy sand, Sassafras sandy loam, and Fort Collins silt loam were treated with a mixed Ca‐Sr solution to give about 95% saturation with Ca and 5% saturation with Sr. Samples of these soils were placed in acrylic cylinders and leached with 0.06NCaCl2to remove Sr. The leachings were mechanically controlled at various rates for different periods of time. Extracting the leached soil samples with 1NHCl yielded residual Sr equal to 0.43, 0.47, and 0% of the Sr exchange capacity of the Evesboro, Sassafras, and Fort Collins soils, respectively. There was general agreement between Sr concentrations measured at various depths and those calculated on the basis of the Lapidus‐Amundson equation, especially so with heavier soils. The Evesboro and Fort Collins soils were also tagged with carrier‐free 85Sr and, mounted in columns, leached with 0.06Nsolutions of either CaCl2or SrCl2. The removal of 85Sr was more complete from the Evesboro than from the Fort Collins soil, and from the center than from the edge of the columns. Short‐term leaching capability of SrCl2exceeded that of CaCl2where 85Sr was present in amounts small enough to be adsorbed mostly on specific soil adsorption sites. Where larger amounts of 85Sr had been adsorbed, Ca was equally effective as Sr in replacing the contaminant.

Two additional initiation factors (IF-M4 and IF-M5) have been purified and characterized both physically and biologically. IF-M4 is active as a single polypeptide chain with a molecular weight of 48,000. In contrast, IF-M5 is active as a complex with a molecular weight of about 500,000 and consists of seven major and several minor polypeptide components. Analysis of IF-M5 in two polyacrylamide gel electrophoresis systems indicated that one of the major polypeptide chains of IF-M5 was the 35,000 dalton subunit of IF-MP. This analysis also revealed that IF-M2A, IF-M3, and elongation factor 2 were present as minor components. Both IF-M4 and IF-M5 are required to achieve maximal activity in an assay system dependent on exogenous globin mRNA, but neither factor has been observed to stimulate model reactions that utilize artificial templates [poly(U) or AUG].

Many sources of irrigation water have sufficiently high Na+/Ca2+ratios to be harmful to soils and crops. When the salt contents of the waters are reasonably low, the primary method of lowering this ratio is to apply extra Ca2+on the fields or in the water. Gypsum is generally the most reasonably priced source of Ca2+. A major portion of its current cost is associated with grinding the stones to a powder and application of this powder to the fields. This study shows that gypsum stones 5 to 20 kg in size are a useable source of the Ca2+needed to bring down the sodium adsorption ratio (SAR) in sodic irrigation waters. The dissolution rate of the gypsum stones is proportional to the square root of the velocity of flow through the bed. Since the time of residence of solution in the bed is inversely proportional to its velocity through the bed, the increase in concentration of Ca2+in solution as it passes through the whole bed is inversely proportional to the square root of the velocity of flow. Solution concentration is also inversely proportional to the square root of the size of the stones in the bed. Equations were developed to facilitate design of channels with the proper cross section and length to supply the needed amounts of Ca2+to the water when the average size of the stones, the flow rate of the water, and the initial ionic concentration of the water are known.

Factors influencing the development of a scientist are discussed. The most important factors motivating a scientist to greater effort are generally those provided by fellow scientists and the people whom we serve. These factors include assurance that his objectives are worthwhile, recognition of his efforts, and the opportunity to publish the truth as he sees it and bear the consequences of his actions. Budget, technical help, and facilities are also important factors determining his production. However, the development of an enterprising scientist cannot be prevented and may sometimes be accelerated by deficiencies in his physical environment.

The amount of irrigation necessary to limit salinity in the plant root zone to concentrations equal to or less than 8 mmho/cm was computed from the consumptive use, rainfall, and salinity of the irrigation water, assuming completely homogeneous plots. Heterogeneity of infiltration rates within plots required that the amount of water applied be 10 to 20% higher than in the theoretical homogeneous case in order to maintain adequate salt removal. Irrigation at 30% higher than the need for the homogeneous case resulted in reduced yields and reduced N content of wheatgrass in areas of high infiltration within the plots. Irrigation at 6% higher than necessary for the homogeneous case resulted in accumulation of salts in areas of low infiltration.

Self‐diffusion coefficients of P in soil were measured by two independent methods and by calculating Dpfrom chloride diffusion. All three methods yielded similar values for Dpat low moisture suctions. On Apishapa silty clay loam, values of Dpranged from 0.4 × 10‐7to 15.5 × 10‐7cm2/sec as the volumetric moisture content increased from 0.22 to 0.55, or as the soil moisture suction decreased from 6 to < 0.1 bar. From these values of Dpa self‐diffusion coefficient for P in bulk solution was calculated, which agreed closely with the experimentally measured value. The transient state method required a separate evaluation of a capacity factor which varied between 100 to 300. If this capacity factor had been omitted, the apparent Dpwould have been smaller by 100‐ to 300‐fold. These results demonstrate the necessity of measuring a capacity factor when Dpis to be determined by a transient state method.

An equation was derived to measure the effect of salt and water diffusion on salt reduction of solutions forced through thin films of water by pressure differentials. Salt concentrations of solutions which had passed through thin films adjacent to charged particles were calculated from the equation and are plotted as a function of pressure differential, ionic mobility, film thicknesses, and cation valences. Experimental evidence showed that salt sieving increases as the pressure forcing solution through the clays increases. Salt sieving generally increases as the pores through which the water flows decrease in size, and is smaller when the soil is saturated with divalent rather than monovalent ions. These observations were in agreement with the theory.

Mobility of water adjacent to Na‐ and Ca‐saturated bentonite surfaces was estimated from diffusion rates of deuterium hydroxide in oriented clay pastes at several moisture contents. The first molecular layer of adsorbed water on Na‐ and Ca‐clays had mobilities which were 30 and 5%, respectively, of the mobility of water molecules in bulk water. There was an indication of a slight reduction in mobility of water as far as 40Å. From the sodium‐saturated clay. However, water more than three molecular layers from the solid surface had mobilities which were 60% of the mobility in bulk water. The mobility data indicate that water outside the first adsorbed molecular layer does not have viscosities more than 2.5 times the viscosity of bulk water.

Osmotic pressures across compacted clays were measured. These pressures were compared with pressures calculated from theory developed in the first paper of this series. Tortuosities and effective thicknesses of films in which water flows, which are necessary for these calculations, were calculated from hydraulic conductivity and salt diffusion data. The measured and calculated values of osmotic pressure were in fair agreement and probable reasons were given for the discrepancies observed. The qualitative agreement supports the assumptions and theory developed in paper I of this series.

The macroscopically observed laws of viscous and diffusive flows were extrapolated to flow of water in thin films in porous media. Correction factors were developed to account for the effects of the diffuse layer of adsorbed cations and greater viscosity of water near particle surfaces. Equations for the two types of flow are combined to give a relationship from which molar free energy gradients can be evaluated in comparison with pressure gradients, as to their abilities to move water.

Chloride diffusivities were measured in medium‐ and fine‐textured soils at moisture tensions from 1/3 to 15 atm. Chloride diffusivities obtained from the soil systems were divided by the diffusivity of chloride in water to obtain transmission factors. These factors varied from 0.310 to 0.027 depending on the soil moisture content and soil texture. The results were interpreted in terms of volumetric moisture content, effective path length factors and clay‐water interactions.

Theory is developed and the effect of the ions and the electrostatic charge associated with clay platelets on the movement of water and ions in thin films between particles or on particle surfaces is calculated for several systems. Under postulated conditions which probably exist in fairly dry soils and compacted shales, movement of water was restricted by as much as 50% and movement of free electrolyte by more than 90%. Data are presented which illustrate this “salt‐sieving” effect and provide a “semiquantitative” check on the theory and calculations. Increases in apparent intrinsic permeability with increasing hydraulic pressure gradients in clay systems, which have been noted previously, are of an order which could be explained by the phenomena considered in this study.

A modification of the glycol retention method for estimating hydrateable surface areas is proposed. In this modification, a large amount of glycol‐bentonite mixture, containing just enough glycol to form a monolayer on all bentonite surfaces, is used to “buffer” the glycol vapor pressure in an evacuated desiccator. Dry and glycol‐saturated samples placed in the desiccator then gain and lose glycol, respectively, until approximately a monolayer exists on all hydrateable surfaces at equilibrium. The average amount of glycol on the two samples at this equilibrium is used, as in previous glycol retention methods, to estimate the hydrateable surface area. The Bower and Gschwend procedure is used to estimate the amount of glycol necessary to form a complete monolayer on all surfaces of the bentonite to be used in the buffer mixture. This amount of glycol is much easier to estimate in a fairly pure clay with large, well characterized surface area than in soil samples, and some possible errors of former techniques may be avoided by the proposed procedure.

The highest yield was obtained on the 53% water‐stable aggregate treatment, indicating that natural aggregate stability levels may have been higher than those required for optimum yield of corn tops. Corn roots growing in conjunction with the soil microorganisms depleted the oxygen supply of the soil air to somewhat lower values than did the organisms alone. Rate of oxygen use per cc. of roots was greatest at higher oxygen levels and fell off sharply with decrease in oxygen content of soil air.

Equivalentconductivities of adsorbed cations were determined in clays saturated with Na+, Cs+, Ca++and with mixtures of these cations. Measurements were also made on Ca++clays which had been forced by previous drying into bundles of platelets or tac-toids. The average mobility of adsorbed Ca++and Cs+is much lower than that of adsorbed Na+. It was concluded that the average mobility of adsorbed Ca++is low because most of this Ca++is on the internal surfaces of tactoids. Ca++adsorbed between these internal surfaces appears to have a mobility much lower than Ca++on the external surfaces which has a mobility of the same order of magnitude as Na+. Polarization of adsorbed Cs+accounts at least partially for its low mobility in these clays. Demixing of adsorbed cations (segregation with Na+dominant between some platelets and Ca++between others) is suggested as an initial step leading to breakup of a Na+-Ca++clay mass into tactoids. The tactoid model, with Ca++and Na+preferentially on the internal and external surfaces respectively, furnishes an explanation of the instability of clay and soil aggregates with 15% exchangeable sodium.