摘要:

The effect of soil texture and bulk density on calibration of neutron moisture and density probes was investigated for five tropical ferrallitic soils. Soil texture and bulk density were found to have a significant effect on the neutron probe calibration. Fine-textured soil with high content of extractable Fe had an intercept of 0.465 as compared to 0.044 for coarse-textured soil. For 20 percent volumetric moisture content the count ratio changed from 0.568 for dry density of 1.0 g cm−3to 0.943 with twice the value of soil density. Similarly, texture and initial moisture content significantly influenced the density probe calibration. Therefore, widespread heterogeneity of tropical soils limits the usefulness of the neutron-scattering technique as routine method of monitoring soil moisture regimes.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

A method for measuring osmotic potential of solutions and moist saline soils in the field is described. Osmotic potential of moist saline soils is determined by the freezing point depression method using a modified thermistor sensor. The data from such measurements is useful in monitoring changes in soil parameters as they relate to the ecology of salt marshes.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

The filter paper method for measuring soil water potential was evaluated. The method was calibrated using salt solutions, thermocouple psychrometer, pressure plates, and soil columns at equilibrium. The predicted water potential was influenced by the type of contact of the soil with the filter paper. It is suggested that one filter paper be placed beneath the soil (good contact for liquid flow and vapor flow) and one filter paper be placed above the soil not in physical contact (allowing vapor flow only). It was found that the absolute temperature was not too important but temperature variations had a large effect on the predicted soil water potential.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Data on the activity of potassium ions in soil pastes prepared with solutions of different total salt concentration were obtained experimentally, and were examined using the methods developed in Part 1.It was found that the average fraction active of potassium was 0.0078 (range 0.001 to 0.040) and the average relative contribution of adsorbed potassium to the direct activity reading in the paste was 0.096 (range 0 to 0.27). The activity in soil pastes made with calcium chloride solutions was higher than in the water paste. This could be accounted for on the basis of the theoretical considerations and the hypothesis presented.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Toxaphene is partitioned between a soil and a solvent in accord with its chemical structure and that of the soil and solvent. Direction of approach (i.e., adsorption or desorption), soil/solvent ratio, type of soil, and type of solvent affect the equilibrium distribution. In the presence of an “infinite” number of soil sites and an “infinite” number of solvent sites the partition is approximately linear. As functional soil sites become limiting, solvent sites become dominant and the partition becomes curvilinear. The curvilinear response can be translated to “monolayer” concentration and amount of covered surface area. For example, toxaphene adsorbed by Cecil B2t soil from acetonitrile solution covers only a small fraction (about 1 percent) of the total surface area of the soil.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

The thermoluminescent characteristics of 15 soil and 73 mineral and rock samples were examined. The soils of widely different chemical types showed wide range of thermoluminescent characteristics. Generally, soils high in lime content showed very high TL. One soil, which was relatively high in free iron content exhibited no TL. The natural TL of soils appeared to be affected by the kinds and amounts of mineral and rock materials present. Since the TL of the different samples even of the same mineral species varied widely, there appeared to be no criterion by which minerals could be identified or classified on the basis of their natural TL. Different lots of samples, however, might be differentiated from each other. Most soils and minerals showed only little, if any, TL below 200°C.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Experiments were conducted to determine the effect of root/suspension ratio on the availability of Ca and K to excised corn roots in bentonite suspensions. Uptake of Ca increased as the ratio was raised from 0.16 to 3.8 g/liter in systems which were well stirred during the uptake period. Potassium uptake was not affected over this range. When the effective root/suspension ratio was varied by regulating the flow of suspension through a fixed quantity of roots, K uptake was much less at a high root/suspension ratio (no-flow condition) than at a low ratio. Calcium uptake was affected in a similar manner, but to a lesser degree. A comparison of mung bean, soybean, corn, and wheat showed marked differences between species in the effect of suspension flow on the availability of Ca and K. It is concluded that the usual experimental techniques employed in excised root studies tend to minimize the effect of an interaction between roots and clay particles, making the results less relevant to natural conditions.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Although trickle irrigation offers the possibility of obtaining comparatively good yields when nontoxic highly saline water is used for irrigation, the subsequent accumulation of salts in the root zone is a potential hazard that should not be disregarded.The objective of this investigation was to determine experimentally the soil water potential and salt patterns in uniform soil profiles as a result of four different water management treatments. Under these treatments cherry tomato plants were irrigated (a) daily with a volume of water equal to that used by the plant on the previous day, (b) every other day with volumes of water equal, (c) below, and (d) above the water evapotranspired.In general, the soil water potential decreased in the soil profile, as a result of salt accumulation, with increased distance from the trickle source. In the profiles where the wetting fronts reached the mid-region between the emitters much lower soil water potentials were measured near the soil surface. The highest salt concentration occurred in the profiles irrigated with volumes of water below that evapotranspired by the tomato plants, indicating the importance of avoiding under irrigation whenever highly saline water is used with trickle irrigation. Higher soil water potentials and higher yields resulted from irrigating with volumes above the evapotranspiration.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Ascospores ofNeurospora tetraspermagerminated on topsoils of forest but not agricultural Hydrol Humic Latosols (Hydrendept). All the agricultural and some of the forest subsoils were inhibitory to spore germination. There was no correlation between pH or organic matter content and spore germination on soils. Results showed that all the major plant species in the forest accumulated a higher concentration of Al from soil than the sugar cane on the agricultural land. The biomass of the total forest plants also was much greater than that of the sugar cane. It is postulated, therefore, that effective accumulation of free Al ion from soil by forest plants results in decrease of fungitoxicity in forest soils.

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1974

数据来源: OVID