摘要:

Thermoluminescent decay of five different types of soils (soil no. 4FF, Yolo sandy loam, Hanford sandy loam, soil no. 9RDG, and Egbert muck) irradiated by Co60 photons and in the reactor were examined.Although the glow output and the glow curve shapes differed considerably among the soils, the shape of the thermoluminescent decay curves, in general, were quite similar, whether the soil was irradiated by Co60 photons or in the reactor. Regardless of the soil type, the most rapid decay occurred within the first 24 hr after irradiation. After the lapse of sufficient decay time, an apparent isothermal equilibrium state was approached. Curves were fitted to the decay data by the use of a computer program which obtains a weighted least squares fit of a function to the data by means of stepwise Gauss-Newton iterations on the parameters. The results indicated that the thermoluminescent decay curves of soils were hyperbolic [Y= α(β +X)γ+ δ] in form.

ISSN:0038-075X    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

Fifteen-bar percentage is estimated after desorption of a wet soil by hectorite for a specified time that varies with the amount of organic matter, clay, and pyroclastics and with the dominant mineral in the soil. The determination can be completed within 26 to 36 hr. Two simple procedures for drying the soil at 105°C are presented. The method for estimating 15-bar percentage should be useful to soil scientists at field facilities as a criterion in soil classification and for estimating wilting percentage.

ISSN:0038-075X    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

The effect of N-serve in controlling nitrification in Australian soils was studied. In an Urrbrae soil that had previously grown pasture for 16 years, an N-serve concentration equal to 5.0 percent of the added fertilizer N was required to reduce nitrification. In a frequently cropped soil, a 0.2 percent concentration was equally effective in controlling nitrification as higher concentrations of the inhibitor. When the inhibitor was added to 16 different soils, it was shown that the extent of the reduction and longevity of the inhibitor depended on soil type. This was confirmed with N15studies.When N-serve was added with NH4+-N to two Urrbrae soils under simulated field conditions, the inhibition was greater in a wheat fallow soil than in a pasture soil.N-serve, when applied with fertilizer N to wheat on the Urrbrae soil, did not significantly increase grain yields.

ISSN:0038-075X    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

Oxygen uptake was determined by manometric methods on the microorganisms in a greenhouse potting soil, a bacterial isolate from this soil, and a bacterial isolate from a peach orchard soil, using as carbon sources the systemic fungicide Benlate (Fungicide 1991, 50 percent wettable powder active ingredient) and the active component benomyl (reagent grade methyl l-(butylcarbamoyl)-2-benzimidazolecarbamate). Uptake by the microorganisms in the greenhouse potting soil was higher in systems containing Benlate than in those without the fungicide. A bacterial isolate (Achromobactersp.) from the greenhouse potting soil, showed higher trends in oxygen uptake with autoclaved soil plus Benlate than in soil with benomyl added at the same concentration. Oxygen uptake by a bacterial isolate from a peach orchard soil (Achromobactersp.) was significantly higher in a system with benomyl, inorganic salts, and glucose than in the same system with Benlate, suggesting an additive effect by benomyl. Results with the bacterial isolate from the peach orchard soil where the fungicide and benomyl were added at the 16-hr time indicated that Benlate and benomyl were inhibitory to oxygen uptake once respiration had begun.

ISSN:0038-075X    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

Diffusion theory was used to describe Fe uptake by sorghum plants in short-term uptake studies. Diffusion equations were used to calculate the concentration of Fe at the surface of roots as a function of time, the extent of depletion zones around roots, and Fe uptake rates.Calculated concentrations of chelated Fe at root surfaces decreased rapidly with time in chelated Fe treatments. However, soluble Fe concentrations decreased much less in nonchelated treatments. Calculated depletion zones were greatest for chelated systems with small capacity factors but decreased as the capacity factor increased. Predicted Fe uptake rates agreed fairly well with observed uptake values from a short-term uptake study.

ISSN:0038-075X    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

The adsorption and desorption of diquat and paraquat on eight arid-zone soils were studied. Adsorption of the two organic cations on the soils conformed quite well with the linear form of Langmuir equation. Practically the adsorption maximum of a given soil for diquat may be considered similar to that of paraquat. The adsorption maxima obtained for the eight soils ranged from 17 to 47 me/100 g. The CEC of a soil was found to be the determining factor of diquat (r= 0.946) and paraquat (r = 0.932) adsorption.The strong adsorption capacities of the soil ranged from 9 to either 23 or 21 me/100 g for diquat or paraquat, respectively. This corresponds to a range of 1930 to 4500 tons/ acre-in. for diquat or paraquat, respectively. It was thus concluded that these herbicides do not constitute any residue hazard.Less than 1 percent and about 50 percent of the adsorbed organic cations could be released with water and 1 M BaCl2, respectively, from the two soils considered.

ISSN:0038-075X    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

The effect of organic sources on the degradation of parathion via nitrogroup reduction and hydrolysis in flooded alluvial soil was investigated. Parathion residues in the soils were extracted with solvent and separated by thin-layer chromatography. Parathion was assayed colorimetrically after its conversion to p-nitrophenol by alkaline hydrolysis. Generally, organic sources accelerated the nitrogroup reduction of parathion. The degradation followed the order glucose > rice straw > algal crust > farmyard manure > unamended. On the other hand, in soils inoculated with parathion-hydrolyzing enrichment culture, organic amendments inhibited the hydrolysis. The rate of hydrolysis in different amendments followed a reverse order of that for nitrogroup reduction. Isotope experiments revealed more rapid conversion of parathion to aminoparathion and an unidentified metabolite in rice straw amended soil than in unamended soil. These metabolites were formed rapidly also in soils amended with other organic sources. In unamended soil, a polar unidentified metabolite was detected. The common practice of incorporating organic materials in rice culture tends to influence the detoxication of parathion in the rice soil environment depending on the pathway involved.

ISSN:0038-075X    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

Molybdate solutions were mixed with soil and incubated at constant temperatures for up to 224 days. The uptake of molybdate by plants was then measured. Uptake decreased with increasing period of contact. The rate of decrease was greatest when the temperature of incubation was high.It is argued that the decreased uptake was due to slow conversion of the adsorbed molybdate into a more tightly bound form. This process was studied by measuring its effect on the concentration of molybdate in solutions in equilibrium with the soil. Equations were developed to describe the effects of time and temperature on the decrease in solution concentration. As had been observed in analogous work with phosphate, these equations described the effects closely. Neither the rate of change of concentration nor the effects of temperature on the change was related to soil pH.Because high temperatures of incubation accelerated the change to a more tightly bound form, they also resulted in low solution concentration. However, the equilibrium between adsorbed molybdate and solution molybdate was affected differently by temperature, and high temperatures resulted in high solution concentration. Hence the adsorption reaction was exothermic.

ISSN:0038-075X    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

Known amounts of phosphate were added to a series of soils and, after incubation at constant temperature, desorption was measured by shaking the soils with a range of volumes of phosphate-free solutions. When the method of shaking was vigorous, an initial desorption of phosphate was followed by an apparent resorption. Since this did not happen when shaking was gentle, it was thought to be due to breakdown of soil particles and exposure of new surfaces. When gentle shaking was used, desorption was almost complete within a few hours when the solution:soil ratio was small but continued up to at least 96 hr when the ratio was large.The amount of phosphate which could be desorbed decreased as the period of prior contact between soil and phosphate increased. The rate and amount of desorption could be described by an equation which indicated that the proportion of the phosphate which could be desorbed increased with a fractional power of the period of desorption, and decreased with a fractional power of the period of prior contact. The amount of desorption also depended on intrinsic soil properties and it was found that, for a range of soils, a parameter reflecting desorption was highly correlated with a measure of adsorption.

ISSN:0038-075X    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

An extruder and cutting system are described for obtaining thin sections of flooded soil from glass tubes.

ISSN:0038-075X    

出版商:OVID    

年代:1975

数据来源: OVID