摘要:

It is often assumed that the distribution of static soil properties is normal and that of dynamic properties (involving flow), for the same pore structure, is lognormal. We examined this assumption to a particular model in which the hydraulic conductivity is derivable from the distribution of pore sizes, numbers, and locations, using Poiseuille's law. The resulting distribution of flow is not exactly lognormal, but is approximately so under certain conditions. A difficulty in interpreting soil data at the high-intensity limit (intensity of pores per unit area) is pointed out.

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

We analyzed grass samples, collected from different naturally occurring grasslands of the Himalayan region, to determine concentrations of trace and major elements in the grasses. These concentrations were related to the concentrations of these elements in soils, soil chemical properties, and climatic factors.Means and ranges of the trace and major elements in the grasses are presented and discussed locationwise and for the whole sampled area. There were manifold variations in the concentration of most of the trace elements in the grasses collected either from different sites at the same location or from different locations. Differences in the concentration of major elements were relatively small. A number of the grasses from humid or subhumid temperate zones were richer in the trace elements, viz., Zn, Cu, Fe, B, Mo, Ni, and Co, and in all major elements compared with those from the subhumid tropical or wet temperate zones.There were highly significant correlations between the concentrations of Zn, Mn, Cd, and B in the grasses and in the soils. The concentration of these elements in the grasses was also significantly correlated with a number of interacting elements in the soils. The other elements, for example, Cu, Co, and Mo, in the grasses did not show significant correlation with their concentrations in the soils, though they showed significant correlations with other interacting elements in the soil.Some of the trace elements, viz., Mn and B, and all the major elements in the grasses were significantly correlated with soil pH. All the micronutrients and some of the major elements were highly correlated with soil organic matter, but only a few of the elements in the grasses showed any correlation with cation exchange capacity. Zinc, Fe, Cd, Ni, B, Mo, and all the major elements showed significant correlations with CaCO3. A number of the trace elements in the grasses were interrelated. We observed an overall trend for concentrations of trace and major elements in the grasses to increase with elevation and decrease with rainfall and temperature.None of the grass samples analyzed was deficient in Zn, Cu, and Fe for normal plant growth, but about 2, 76, 2, 17–76, 21, 44, 6, and 73% of the grass samples may be considered deficient in Mn, B, Mo, N, P, K, Ca, and Mg, respectively. The percentage of the grass samples that may not meet the dietary requirements of sheep and cattle was 55 for Zn, 5 for Mn, 55 for Cu, 23 for Mo, 90 for I and Se, 15 for Co, 20–35 for N, 40 for P, 34 for K, 6 for Ca, 73 for Mg and 100 for Na.

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

We investigated the seasonal variation of water-soluble phosphate (P) in a Sultan silt loam (Aquic Xerofluvents) with and without wheat or corn residue amendment. The soil was cropped to corn (Zea maysL.) immediately after the residues were incorporated. The P soluble in water and pH for the soil showed a similar annual pattern regardless of residue treatments; they were generally low during the drier and warmer spring and summer, gradually increased in the fall, and reached a maximum during the winter high-rainfall period. High correlations between water-soluble P and soil pH (r= 0.75–0.88,P< 0.01) and between water-soluble P and inorganic N (NH+4-N and NO−3-N)r= −0.65–0.88,P< 0.01, depending on residue treatment) were observed, indicating that the seasonal variations of water-soluble P could largely be explained by these two soil characteristics. Because soil pH and water-soluble P were both negatively correlated with temperature and with NO−3-N levels in the soil and could be further decreased with increasing rates of N application, the biological mineralization of organic N and the transformation of NH+4-N to NO−3-N likely played an active role in the seasonal pattern of water-soluble P in the soil.

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Handling of soil materials during surface mining may substantially modify their physical and chemical properties. In this report, a comparison is presented among: (1) bulk density, (2) particle-size distribution, (3) soil reaction, and (4) organic matter content of soils on natural and reclaimed hillslopes at the Dave Johnston Mine, Glenrock, Wyoming. At this site, no significant difference occurred in bulk density between the soils of natural and reclaimed hillslopes. No significant difference occurred in gravel content, but sand content was significantly higher on the soils of natural sites than on those of reclaimed sites. There were no significant difference in average pH between the soils of the natural and reclaimed hillslopes for the first decimeter of depth; however, the average pH of soils on the reclaimed hillslopes was significantly lower than those on the reclaimed hillslopes for the second, third, and fourth decimeters. Finally, no significant difference occurred in organic matter values between the soils of natural and reclaimed hillslopes for the first decimeter, but the difference was significant in the second decimeter.

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Because pedoturbation processes (soil mixing) occur in all soils in varying degrees during the curse of their evolution, mixing processes should be assessed within the larger context of soil genesis. Soils may be viewed as evolving along two pedogenic pathways that operate concurrently: a progressive pathway that includes processes, factors, and conditions that promote ordered, differentiated and/or deep profiles; and a regressive pathway that promotes disordered, simplified, rejuvenated, and/or shallow profiles. Pedoturbative processes that disrupt, blend, destroy, or prevent the formation of horizons, subhorizons, or genetic layers, such that simplified profiles evolve from more ordered ones, areproisotropicand function within the regressive pathway. Pedoturbative processes that form or aid in the formation and maintenance of horizons, subhorizons, or genetic layers and/or promote increased profile order areproanisotropicand function within the progressive pathway.Ten forms of pedoturbation are recognized. Hypothetical and real examples of how proisotropic and proanisotropic mixing processes affect soil profiles are presented. The examples demonstrate that both theformof pedoturbation and thetextureof the parent material largely determine whether the ensuing morphology of a soil expresses order or disorder. A particular form of pedoturbation may produce a disordered profile in one soils or polypedon, but a more ordered profile in another. This can be true not only for different soils on a landscape, but also for the same soil at different times during its evolution. Homogeneous or heterogeneous geologic deposits may be pedologically organized, or reorganized, via proanisotropic pedoturbation to express profile order and in certain cases may produce spatial patterning and microrelief. Surface stone pavements and armored surfaces, subsurface stone lines and stone zones, and upper profile biomantles can thus be formed.

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

This paper reports a model for the flow of two incompressible and immiscible fluids in soils, developed by combining a modified Darcy's law with the continuity equations. The resulting equations are of a system of nonlinear partial differential equations. Numerical analysis, based on the finite element method and Newton-Raphson's method, to solve the equations is given and discussed. Computer simulations of the flow of water and trichloroethylene in sands are also shown.

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Ten acid sources, including granular and powdered forms of elemental S, iron sulfate slag, ferrous sulfate, and ammonium sulfate were added in equivalent amounts to two Histosols and three Alfisols typical of soils from the Everglades, and the soils were incubated for over 6 mo. At 2240 kg S ha−1, the powdered form of S was more effective in lowering soil pH than the granular sources of S. Little difference was found between the granular S products. Ferrous sulfate and ammonium sulfate lowered soil pH more than the elemental S products.

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1987

数据来源: OVID