摘要:

The unsaturated hydraulic conductivity function for soil can be calculated directly from a moisture retention function and a single measurement of hydraulic conductivity at some water content. If the moisture retention function can be represented by ψ = ψc(&thetas;/&thetas;a)−b, where ψcis the air entry water potential, &thetas;, is the saturated water content, andbis an emperically determined constant, then the hydraulic conductivity is given byk = ks(&thetas;/&thetas;s)2b+3, whereksis the saturated hydraulic conductivity. Agreement ofkcalculated using this procedure with experimentally determined conductivities for five soil samples was found to be at least as good as with other calculation procedures.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Since the cost of isotope is a major expense in field experiments utilizing15N-labeled fertilizer, a technique is proposed to reduce the amount of15N required. This technique can effect a considerable saving since only one band of labeled fertilizer N is required per plot.In two experiments where fertilizer was banded midway between rows spaced 76 cm apart, corn plants did not take up important amounts of labeled N fertilizer from a band more than one row away. Since virtually all fertilizer N is taken up from the bands adjacent to the row, only one band in each plot need be labeled. Fertilizer of normal15N abundance is satisfactory in the bands in the remainder of the plot area. After adequate samples of plants are taken for isotopic and chemical analyses from rows on each side of the fertilizer band in each plot, the entire plots may be harvested in the usual manner for yields and other measurements. Plot sizes and experimental designs may be those normally used in similar field experiments.Since uptake by plants on opposite sides of the fertilizer band may not be the same, adequate samples of plants must be taken from the first row on each side of the band of15N-labeled fertilizer. Nitrogen contents and isotopic ratios must be determined on both samples and calculations of uptake of fertilizer N should then be based on twice the mean of the fertilizer N in the two rows.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Humic acids from the A1horizon of a Chernozem black soil and from a weathered medium volatile bituminous coal were treated with a selective oxidant, namely sodium hypochlorite solution. Over 50 percent of the total carbon in both the humic acids appeared as CO2. Coal humic acid furnished predominantly benzene carboxylic acids, while the soil humic acid yielded a high proportion of aliphatic mono-, di-, and tricarboxylic acids. A good carbon balance indicates the complete oxidation of both the humic acids.Proceeding from the known chemistry of hypohalite oxidation, it is concluded that soil humic acids represent a special group of mixed alkyl-aryl-cycloalkyl compounds in which Sp2carbon represents over 80 percent of the total carbon. If such humic acids are accepted as precursors of coal formation, the present study indicates that “maturation” converts the cyclo-alkyl skeletal arrangements of the component molecules from a normal bicyclo- or hydro-aromatic system to a bridged tricyclo- or more complex system at the expense of longer alkyl chains.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Using nondestructive measurements the simultaneous transport of chloride and water was examined for infiltration and redistribution within laboratory soil columns. Chloride, either spread on the soil surface or initially dispersed throughout the soil to simulate a salt-affected soil, was leached with chloride-free water (0.01NCaSO4). Water application methods yielding small average soil water contents during infiltration leached the chloride efficiently and to relatively greater depths. Although the initial soil water content prior to leaching did not have any appreciable effect on leaching during infiltration, the smaller the initial soil water content, the deeper and more complete was the displacement of chloride during redistribution for a given quantity of water applied.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

The dependence of gamma-ray attenuation on the chemical composition of soils is investigated in the energy range from 10 keV to 3 MeV. Mass attenuation coefficients have been calculated for five soil types, showing appreciable variations with soil composition in the region of gamma-ray energies up to a maximum of 300 keV.The influence of the chemical composition of the soil on the determination of dry bulk density and moisture content by the gamma-ray attenuation method is considered.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Information relative to the compositions of ironstone glaebules and enclosing soil material in soils is limited. An investigation was begun to determine the chemical and mineral compositions of glaebules and enclosing soil materials as a function of soil depth in a Southern Coastal Plain soil (Plinthic Paleudult). Bulk chemical analysis by X-ray spectrography showed that both glaebules and enclosing soil material were composed primarily of varying amounts of Fe, Si, and Al. Mineralogical examination by X-ray diffraction revealed that the dominant minerals in glaebules and soil were quartz (primary skeletal grains), kaolinite, gibbsite, goethite, and in glaebules of the surface horizon, hematite. Differences between glaebules and enclosing soil material decreased with soil depth in both chemical composition and mineralogy. This indicated that glaebules and soil in the surface horizons originated from material similar to the subsurface material. Data indicate that glaebules originated from plinthite due to leaching and destruction of kaolinite, removal of silica, and conversion of goethite to hematite (dehydration). The resulting glaebules in surface horizons were rich in ses-quioxides of Fe and Al. Surface horizon soil material, on the other hand, was rich in quartz and depleted of sesquioxides of Fe and Al. The large differences between the composition of glaebules and soil in surface horizons indicated that separate mechanisms were involved in their formation. Laterization processes appeared to be involved in glaebule formation whereas podzolization processes were apparently responsible for soil horizon development.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Low readings of oxygen partial pressure of as much as −25 percent were caused by the condensation of water on single-membrane, 0.5-mm-radius oxygen cathode P02sensors in soil.A double membrane arrangement like the improved membrane system of Enoch and Falkenflug was effective in eliminating condensation as a source of error in the P02sensor measurement.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Bush beans (Phaseolus vulgarisL. var. Improved Tendergreen) were grown in solution and in soil with different levels of added P. When the Zn supply was low in solution culture, increasing the P supply decreased the absolute uptake of Zn, decreased its contents in all plant parts, decreased the proportion of total amount of it in roots, but increased the ratio of ppm Zn in roots to that in leaves. When the Zn supply was high, increasing the P supply resulted in increased absolute uptake of Zn and increased the content of it in plant parts, but did not materially change the proportion in roots compared with shoots. Iron contents were usually decreased by the increasing P levels. When KH2PO4(0 to 2500 ppm P in soil) was applied to Yolo loam soil, yields were not influenced, but P and Zn contents of all plant parts were. The 50 ppm P level decreased Zn concentrations in shoots, but higher P levels increased them. Cu, Fe, Sr, and Ba (greatly) contents were decreased by the high P levels. Soil pH may partially explain some of the results.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

The soils of Sleeper Islands, Hudson Bay, are described. Two main soil groups are extensive: lithic regosols on basaltic rock, and calcareous regosols on shell deposits characterized by the dominance ofMytilus edulisorHiatella arctica. The most developed soils are eutric brunisols. The chemical properties of organic horizons emphasize the influence of salt spray on these soils. Periglacial action reworks shell deposits and has some effects on soils.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Fruit production and tree growth characteristics of a Valencia orange orchard are related to equilibrium distribution of salts throughout the root profile in response to uniform applications of irrigation waters varying in salinity and sodicity hazards. Eight years of differential irrigation treatments consisting of basin irrigation with four waters representing low to moderately high salinity, and also with Cl and SO4waters, resulted in soil salinity profiles specific for each water. Both the quantity and quality of oranges have declined under irrigation treatments producing accumulation of soluble salts within the rootzone. Specific ion, osmotic, and soil suction effects are discussed in relation to salinity stress.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID