摘要:

Changes in redox potential, soil gas composition (O2and CO2), and oxygen diffusion rate were studied in laboratory soil columns in the presence of different stagnating groundwater tables. Under steady-state moisture conditions, a decrease in O2content was reflected by an increase in CO2content. The redox potential was related to the soil pH. The oxygen diffusion rate increased when the water table was lowered. Only at water table depths of more than 50 cm did the oxygen diffusion rate at the 5-cm soil depth exceed the level at which aeration is considered sufficient to sustain vigorous rooth growth.Empirical relations are presented for calculating the aeration profile in soils from water pressure head measurements with tensiometers. Redox potential measurements did not reflect the soil aeration status in oxygen-rich environments.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

The age of deposition of an aeolian deposit such as loess may be found using thermoluminescence (TL) measurements to obtain the radiation dose that the deposit has received since that time. The radiation dose received by unseparated 4− to 11-micrometer grains extracted from a late Devensian loess is found to be the same as that received by 4− to 11-±m quartz grains extracted from the same sample. This confirms that the polymineral TL, which is dominated by the feldspar TL, is not subject to anomalous fading. The quartz response is linear up to about 20 kilorads, which allows the dating of samples younger than about 30 kiloyears. However, for larger doses the response appears to saturate, which precludes the use of fine-grain quartz for dating older samples.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

An electrochemical hydrogen sulfide sensor was constructed for use in the measurement of H2S in soils. The pH2S changed nearly linearly with the change of pH, with a slope of 0.8 to 1.1 for the three soils studied. The slope for the dependence of pS2on pH was 1.1 to 1.5. The addition of ferrous iron to the soil resulted in the decrease in the concentration of soluble hydrogen sulfide. There was a peak in H2S concentration after 3 to 4 days' submergence. Later, the H2S concentration may maintain a rather high level, even in the presence of a large amount of water-soluble ferrous iron. The (pFe2++ pS2-) value was not a constant, but decreased with the increase in pH.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

Aqueous extracts of the B horizon from two forest types were fractionated on Sephadex G-25 (medium). Fractionation patterns and spectroscopic data suggest that there are different materials and different metal-organic associations between these two forest types. These observations may partially explain differences in patterns of cation cycling between birch and aspen forests located in similar sites.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

Symptom development ofSclerotiumsp.-incited twin stem abnormality of soybeans (Glycine max(L.) Merr.) was retarded significantly (P= 0.01) when calcium levels in aerial tissues were increased by the addition of calcium carbonate to the soil. Addition of magnesium carbonate to the soil had an inhibitory effect on calcium uptake and enhanced twin stem symptomology, similar to that of untreated plants. Addition of calcium to soils may be a practical approach to overcome the twin stem abnormality in soybeans.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

Greenhouse and laboratory experiments were conducted to characterize the chemical form or forms of Cd, which is a contaminant in phosphate fertilizers, in terms of plant availability and extractability from soil. Winter wheat (Triticum aestivumL.), cv. Nugaines, was grown on Mountview silt loam (limed to pH 5.5 and 7.5) treated with three commercial diammonium phosphate (DAP) products containing 48, 73, and 188 ppm Cd and reagent grade DAP alone (1 ppm Cd) or with added CdCl2to supply 188 ppm Cd. Cadmium concentrations in wheat forage, grain, and straw were significantly increased with increasing Cd concentrations in DAP at both soil pH levels. Concentrations of Cd in plant tissues were higher from reagent DAP containing CdCl2than from commercial DAP containing the same Cd concentration and also were higher in plant tissues from all fertilizer treatments on acid than on alkaline soil. Results of a second greenhouse experiment also showed that Cd concentrations in corn (Zea maysL.) forage from DAP products containing the same concentrations of Cd (131 ppm) decreased in the order: reagent DAP + CdCl2, commercial DAP, and reagent DAP + Cd3(PO4)2.In laboratory experiments, commercial DAP and superphosphate (TSP) containing 188 and 180 ppm Cd, respectively, and reagent DAP containing about the same concentrations of Cd added as several Cd salts were mixed with soil at a rate of 200 ppm P (0.19 ppm Cd). After incubation in moist soil at room temperature, levels of extractable Cd decreased in the order: DAP + CdCl2, commercial DAP and TSP, DAP + Cd(H2PO4)2, DAP + CdHPO4, and DAP + Cd3(PO4)2. Concentrations of Cd in extracts from each treatment in alkaline soil generally were lower than those in extracts from acid soil, followed the same trends with each experiment, and decreased in the order: 0.1NHCl, 0.005MDTPA, and deionized H2O. The decrease in level of extractable Cd in treated soil is in the same order as that of plant uptake results in the greenhouse experiments. Results therefore suggest that the chemical form of Cd contained in TSP and DAP is Cd(H2PO4)2, CdHPO4, or a mixture of these salts, which are Cd analogues of the P compounds in commercial P fertilizers.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

In laboratory studies the herbicide 3-amino-2,5-dichlorobenzoic acid (chloramben) inhibited urea degradation when incubated with soil samples or with a pure culture ofEnterobacter cloacae, a soil isolate. In the field the herbicide was used in conjunction with urea fertilizer in cucumber plantings. Yield was reduced about 20 percent from an average of 466 grams per plant for untreated plots to 379 g/plant in herbicide-treated plots. Fruit from herbicide-treated plots, although similar in nitrogen content to fruit from untreated plots, contained significantly higher concentrations of niacin and ascorbic acid (5.3 milligrams per 100 grams dry weight of niacin and 45 mg/100 g dry weight of ascorbic acid in fruit from treated plots versus 4.8 mg niacin and 18 mg ascorbic acid in fruit from untreated plots). There was no significant difference in thiamin content in fruit from treated or untreated plots. Thus, the herbicide used should be compatible not only with the plant but also with the fertilizer.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

The relative mobility of Cd, Cu, Ni, and Zn added to several soils and the simultaneous desorption and leaching of metals (Ca, Mg, K, Al, Na, heavy metals) were determined by eluting soil columns with 0.01MCaCl2and analyzing the metals in leachates and soil by plasma emission spectroscopy. Although soil chemical properties generally had a larger effect on the mobility of metals than did the properties of the metals themselves, Cu moved least readily through all soil columns. The least mobility of metals was observed in a mineral soil with a relatively high pH, CEC, and exchangeable base content. The liming of an acid mineral soil reduced metal mobility, but not to the extent expected from the very low mobility observed for a naturally nonacid mineral soil. The order of mobility of the metals in the soils was: Cu ≦ Zn ≤ Ni ≤ Cd. These metals were almost completely extractable by 0.1NHCl from a limed and unlimed acid soil, but were less extractable from a nonacid mineral soil and an organic soil. This effect is attributed to partially irreversible binding of the metals in organic matter, a phenomenon inhibited by the presence of Al on organic complexation sites.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

Soil pore water samples are collected by moisture extraction of a soil core or with in situ samplers. Lysimeters are the most common samplers, despite a number of inherent and sampler-related problems. Sampler limitations were minimized through the design and construction of all-Teflon units for shallow and deep sampling. Design features in both units include detachable threaded components, the placement of the hydrophilic section midway on the vessel, and the ability to assemble a unit in the field most suited to the particular soil conditions. Leaching of Ca, Cl, Fe, Mg, Mn, Na, Pb, and Zn standards through the porous Teflon revealed no detectable attenuation. Clogging of the porous section occurred, although the proper installation and backfilling with silica flour minimized this effect.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID