摘要:

Rates of carbon dioxide exchange were determined using an infrared gas analyzer in an open chamber system in a field. During 1971 a fan was used to draw air through the chamber; the measured CO2flux was approximately 40 percent greater than the highest rate reported in the literature. In 1972 two chambers were used: one under slight suction and the other under a slight pressure (compared with atmospheric pressure). The CO2flux from the soil surface inside the “pressure” chamber was nearly an order of magnitude lower than inside the “suction” chamber. Dispersion equations were used to separate mass flow and diffusion components of the total flux. Simplified analysis showed that mass flow could account for the large CO2flux with slight negative pressures inside the chamber.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Dispersion profiles of 2,4-dichlorophenoxyacetic acid in sorbing porous media were measured experimentally to evaluate a theoretical dispersion model previously developed by the investigators. The chemical being dispersed along a column made up of glass beads was initially present only in the pore water of a 1 cm long section at the front of the column. After leaching for a period of time the column was sectioned and the concentration in each section was obtained and compared with a predicted concentration.Four porous media systems consisting of glass beads with particle diameters of <30, 28–53, 105–149, and 149–210 μm obtained by dry sieving were used. Corresponding predominant pore radii were 4.5, 8.2, 19.5, and 36.2 μm. Sorption sites were established on the glass beads by coating them with an ion exchange resin.Experimental results were in good agreement with theoretical predictions.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Studies on the sorption of phosphorus, exchangeable aluminum, exchangeable acidity, and surface area on four soils have been made. The sorption of phosphorus at zero time, which was taken as the time just required to mix 2 g of soil sample with 25 ml of potassium dihydrogen phosphate solution, was found to be in good agreement with the true exchangeable aluminum measured by the graphical method of Sivasubramaniam and Talibudeen (1972). The zero-time phosphorus sorption also correlated with the exchangeable acidity but not with the surface area.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Data from 555 soil profiles were used to determine the factors affecting the pH base-saturation relationship and attempts were made to improve prediction of base-saturation percentage from pH.Base saturation of subsoils within selected pH ranges showed regional variation. A negative correlation, significant at the 1 percent level, was found between base saturation at a given pH and moisture surplus (mean annual precipitation minus potential evapotranspiration) as calculated by Thornthwaite and Mather's mean annual water balance. Significant correlation was not found in poorly and very poorly drained soils. It is suggested that intensity of leaching has affected the base saturation at a given pH.Very little correlation was found between clay mineral types and base saturation at a given pH level. However, a region in northeastern Pennsylvania, with soils high in illite and chlorite, differed from other areas in Pennsylvania in its pH base-saturation relationship.Prediction equations for base-saturation percentage were developed for northeastern Pennsylvania and for the remainder of the state using pH, moisture surplus and drainage class as independent variables.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

A method is proposed for determining the titratable acidity and the total exchangeable base cations by extracting the soil with a solution of 1MNH4Cl-0.1Mimidazole buffered at pH 7.0. In nonsaline soils the cation exchange capacity is obtained as the sum of those two values. The procedure is rapid and accurate compared with the reference methods, regardless of soil type and/or base status.With regard to the calcareous soils, a technique is described for correcting the figure of total exchangeable bases for Ca and Mg dissoluted from soil carbonates which makes use of acidimetric titration of the soil extract.For the determination of the “effective” cation exchange capacity, which more closely reflects the actual cationic composition of the exchanger phase of the acid forest soils, an extraction of the soil with unbuffered 1MNH4Cl solution was found most satisfactory.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Using grain yield as a criterion, optimum concentrations of leaf N in different cultivars of rice were found to differ widely between flooded field culture (1.8 percent N to 2.5 percent N) and nutrient solution culture (3.3 percent N to 3.8 percent N). Comparisons among different cultivars, greenhouse and outdoor culture, full sunlight and 50 percent shading, and between wet season and dry season in a tropical climate (Philippines) failed to produce differences comparable to those observed between field-and solution-cultured plants.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

In view of the difficulties encountered in the determination of soil contents of trace elements available to trees and other mycotrophic plants, the deficiency of micronutrients is best appraised by trial treatments and subsequent foliar analyses of the treated and control plants. The relationships are illustrated by applications of Sequestrene chelated fertilizers and foliar analyses of 2-year-old red pine,Pinus resinosa, and white spruce,Picea glauca, raised in the Hayward, Hugo Sauer, and Griffith State forest nurseries of Wisconsin. The treatment of red pine produced no change in the leaf composition of trees; the treatment of white spruce greatly increased the foliar concentration of not only applied copper and zine, but also all the other major and minor nutrient elements, as well as aluminum.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

A simulation technique, using CSMP language, was designed to study the possible influence of different diffusivity-water content relations on the shape of the soil moisture profile during profile-controlled evaporation. Only the use of a “hooked” diffusivity function (which takes into account the increase in vapor diffusivity in the dry range) resulted in an inflected soil moisture profile, with the inflection point propagating into the soil with the square root of time. Cumulative evaporation was slightly higher in this case than in the cases where the diffusivity continued to decrease, or leveled out, in the dry range. The analysis assumed infinite external evaporativity, and isothermal and homogeneous soil conditions with no gravity or internal drainage effects.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Rhizobium japonicumstrains 117 and 138 (USDA) were used in equal proportions to inoculate soybean seedlings. Preparations of individual nodules were stained with strain-specific fluorescent antibodies and rhizobia present were identified by direct microscopic examination using transmitted tungsten (darkfield) light and reflected near-ultraviolet light singly and in combination. At an inoculation density of 108rhizobia per plant, 32 percent of the nodules contained both strains. The percent double infection decreased as inoculum density decreased. Strain 138 generally predominated over strain 117 in accounting for the majority of the nodules that contained only one strain, and cells of 138 were generally numerically predominant in nodules that contained both strains. Streak plate cultures of selected nodule slurries provided data that fully reinforced the fluorescent-antibody data.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Soil in columns 7 in. deep received 1 mg NO3-N per g of soil and water to bring the soil to 90 percent of saturation (moisture tension 70 cm water). This soil stored at room temperature showed no loss of NO3-N to a depth of 3 in., but at depths between 3 and 4 in. considerable loss of NO3-N occurred which approached losses measured at lower levels to a depth of 7 in. of the soil.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID