摘要:

Soil quality and pedology are similar in their melding of concepts and disciplines and their reliance on the model of soil formation described by Jenny in 1980. They differ in spatial and temporal scales and in the organisms concerned. In this regard, soil quality can be considered part of the science of pedology. Significant differences in selected near-surface soil properties and subsequent interpretations as influenced by land use are illustrative of the need to collect data reflecting use-dependent or dynamic soil properties. Inherent or use-invariant properties dictate the limits to which dynamic properties range. As pedologists begin to explore these relationships, a dynamic soil properties database should be developed as a companion to the database of use-invariant properties used currently for classification, mapping, and interpretation.

ISSN:0038-075X    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Several models have been developed to estimate the water retention curve (WRC) on the basis of the similarity in shape between the WRC and the particle-size distribution (PSD) of a soil. Shortcomings of these models are (i) their adoption of empirical equations for the PSD and WRC and (ii) use of regression equations for the WRC parameters that do not emphasize the physical significance of their model parameters. By applying a lognormal distribution law to the PSD and assuming a lognormal void-size distribution (VSD) and then combining with the WRC function developed by Kosugi in 1996, we developed a simple model for estimating the WRC directly from the PSD. The only parameters that need to be estimated are those defining relationships between particle diameter (d) and pore size (r). Data for 117 sandy soils were extracted from the UNSODA database. The parameters were calibrated for three texture classes within sandy soils used in this study. The model defining the nonlineard-rrelationship (NL model) predicted the WRC better than the model defining the lineard-rrelationship (L model). The L model overpredicted the capillary pressure at high saturations, whereas the opposite was observed at the low saturation region. The inclusion of two parameters that describe the packing characteristic as well as the respective shapes of the particles and the corresponding pores may explain the better performance of the NL model.

ISSN:0038-075X    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Effects of land use and management treatments on soil mechanical and hydrological properties were assessed by analysis of bulk and core soil samples and water infiltration measurements in the field, using double ring infiltrometers in five plots located at the experimental farm of the North Appalachian Experimental Watersheds (NAEW) near Coshocton, Ohio. The five treatments were no-till without manure (NTWM), no-till with manure (NTM), no-till corn (Zee mays)-soybean (Glycine max) rotation (NTCSR), conventional tillage (CT), and meadow (M). Treatments significantly influenced water infiltration characteristics, soil bulk density (&rgr;b), aggregation, and mean weight diameter (MWD). The maximum cumulative infiltration after 3 h (I) of 109.3 ± 29.0 cm (average of 9 measurements at 3 landscape positions) was measured for the NTM treatment and the lowest of 27.7 ± 21.0 cm (average of 3 measurements at shoulder slope or S) for the CT treatment. The infiltration rate at 5 min (i5), steady state infiltration rate after 3 h (ic) and field capacity water content 24 h after the infiltration (FC) were higher in NTM (1.5 cm min−1, 0.4 cm min−1, and 0.35 gg−1, respectively) than other treatments. The least values of i5, icand FC (0.4 cm min−1, 0.18 cm min−1, and 0.22 gg−1, respectively) were observed for the CT treatment. Saturated hydraulic conductivity (Ks) measured on soil cores was the highest for the NTM (0.29 cm min−1) for 0 to 10 cm and NTCSR (0.24 cm min−1) for 10 to 20 cm depth. The &rgr;b(1.52 g cm−3for 0 to 10 cm and 1.62 g cm−3for 10 to 20 cm depth) was the lowest and water stable aggregates (WSA) were the highest (WSA of 89% and 63%) for both depths for the NTM treatment. The &rgr;bwas much higher for the CT (1.75 g cm−3for 0 to 10 cm depth) and NTWM (1.77 g cm−3for 10 to 20 cm depth) than NTM, NTCSR and M treatments for either depth. The landscape positions did not have a significant influence on soil physical and water transmission properties nor on total biomass. The manuring treatment improved soil aggregation and water transmission properties (NTM > NTWM > NTCSR).

ISSN:0038-075X    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Soil structural and water transmission properties, as influenced by land use and soil management, affect the coefficients of infiltration predictive models. Ten infiltration models were analyzed to assess these coefficients. The models tested includeGreen and Ampt (1911),Kostiakov (1932),Horton (1940),Mezencev (1948),Philip (1957),Holtan (1961)—two and three-parameters,Stroosnijder (1976),Swartzendruber (1987), andKutilek and Krejca (1987). Parameters were evaluated for time-dependence and precision and with regard to the effects of land use/soil management and landscape positions. The field water infiltration data used in these models were based on double ring infiltrometer tests conducted for 3 h at six different land use/soil management treatments at the North Appalachian Experimental Watersheds (NAEW) near Coshocton, Ohio. The treatments were no-till without manure (NTWM), no-till with manure (NTM), no-till corn-soybean rotation (NTCSR), conventional tillage (CT), meadow (M) and forest. Measurements were made at three landscape positions (e.g., shoulder or upper slope (US); back or middle slope, (MS); and foot slope (FS)). The algebraic parameters of the infiltration models and nonlinear least squares regression were fitted using measured infiltration time [I (t)] data. Among process-based infiltration models, the Swartzendruber model performed best and matched the measured I (t) data with lower sum of squares (SS) and higher model efficiency (EF) and Wilmot’s index of agreement (W). Overall the three-parameter Horton model gave the best representation of the I (t) relationship with the lowest SS and the highest EF and W for most of the land use treatments, including forest. The treatments had significant influence on the parameters related to initial infiltration rate or sorptivity and final steady state infiltration rate or hydraulic conductivity near saturation, whereas landscape positions had significant influence on the sorptivity parameter only. The fitted parameters (i.e., sorptivity and hydraulic conductivity near saturation) were time dependent and were higher for NTM than for other treatments.

ISSN:0038-075X    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Phosphorus-based nutrient management requires that all sources of P added to fields, including manures, must be accounted for in crop production plans. Nearly 13% of U.S. broiler production occurs in the MidAtlantic region, which generates 720,000 tons of manure annually. Use, treatment, or manure disposal options are important issues in dealing with large volumes of manure; transforming the manure to compost and utilizing it off-farm is one viable utilization option. A study to evaluate plant-available P in poultry litter compost (PLC) compared with triple super phosphate (TSP) was conducted in a growth chamber using fescue (Festuca arundinaceaSchreb). Phosphorus amendments from 0 to 150 mg P kg−1soil were added to Sassafras soil (typic Hapludults, fine-loamy, siliceous, mesic). Nitrogen rates were constant over all P treatments at 150 kg N ha−1. Fescue was harvested three times during an 84-day study, and clippings, as well as roots and crowns at the termination, were analyzed for P content. Cumulative dry weight of fescue clippings was the same for both TSP and PLC and did not change with increased P application from 0 to 150 kg P ha−1soil. These data suggest that the Sassafras soil was not deficient in P (Mehlich 3 extractable P was approximately 125 mg P ha−1) and that the N application rate of 150 kg N ha−1, which was constant across all P treatments, determined yields. Cumulative phosphorus uptake was the same for PLC and TSP but, in this case, was linearly related to P application rate. At the 84-day harvest, greater P uptake was recorded for 100 and 150 kg PLC-P ha−1rates than for all other treatments, which suggested that organic compounds in the PLC may be blocking adsorption sites and/or releasing soluble P with time. Phosphorus uptake by roots and crowns was approximately equal to cumulative P uptake of clippings. Statistical analysis indicated no effect of P source or rate on P uptake by roots and crowns, but only two of four replicates were harvested. Because PLC was equal to TSP in supplying P to fescue, composting of poultry litter does not seem to affect P availability in the same manner as it affects N. Compost application based on crop N needs and N availability will result in greater plant-available P additions than if uncomposted poultry litter is added.

ISSN:0038-075X    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Soil genesis in semiarid climates must consider the influences of aeolian and other forms of sediment deposition, particularly the emplacement of dust and dissolved constituents in rain and sediment trapped by overland flow. The purpose of this study was to explore the possibility of using Ti-indexed elemental concentrations of the fine earth, whole clay fractions, and rock fragments extracted from the soil to propose that the soil’s elemental composition is incompatible with its development exclusively from the underlying igneous parent material. The soil, a member of the Brewster series (Loamy-skeletal, mixed, superactive, thermic Lithic Haplustolls), is located in the Chisos Mountains of Big Bend National Park, Texas. The soil profile descriptions, chemical properties and clay mineralogy are consistent with a limited degree of soil weathering. However the total Ti-indexed concentrations of the macro-elements and the rare earth elements indicate a substantial elemental depletion, suggesting that weathering has been prolonged and intensive. Titanium concentrations in the clay fraction are substantially greater than those of the whole soil, suggesting that external clay additions inflate both the Ti content of the whole soil and the elemental loss estimates. The evolution of these soils is, in part, predicated on external clay additions, with sediment accumulation caused by the trapping of overland flow the most plausible scenario.

ISSN:0038-075X    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Surface horizons of Rhodic Paleudults in the Tennessee Valley region of Alabama contain large amounts of clay (<2 μm) composed of quartz, kaolinite, hydroxy-interlayered vermiculite, and iron oxides. Similar clay mineralogical suites have been shown to be dispersive, which can lead to the degradation of soil physical properties. Furthermore, some studies have suggested mineralogical enrichment in dispersed colloids versusin situsoil, which can effect transport of sediment-attached pollutants. The historical utilization of conventional tillage practices without cover crops has degraded soil quality in this region; however, reduced tillage systems are becoming common. We evaluated clay dispersibility and mineralogical partitioning for fine, kaolinitic, thermic Rhodic Paleudults cropped to cotton (Gossypium hirsutumL.) in: (i) a no-till system without a cover crop (NT), (ii) a no-till system with a rye (Secale cerealeL.) cover crop (NTC), (iii) a no-till system with a rye cover crop and fall paratilling (NTCP), and (iv) a conventional tillage system (disking and chisel plowing in the fall followed by disking in spring) (CT). Water dispersible clay (WDC), extractable Fe, and soil organic carbon (SOC) were evaluated for surface (0–1 cm) samples. Particle size distribution (PSD) and clay mineralogy ofin situsoil, runoff sediment, and WDC were also determined. Data indicated Fe oxides play a more significant role in clay aggregation than soil organic matter (SOM) in these high Fe systems. Higher clay amounts were recovered with dithionite extractable Fe removed (Fed) compared with SOM removal (33 ± 3% vs 25 ± 4%). The WDC quantities were related to SOC (r2= 0.65) and negatively correlated with Fed(%) and water stable aggregates (%). Particle size and mineralogy of runoff sediment and WDC mineralogy were similar toin situsoil, suggesting models depicting erosion and sediment-attached pollutant transport can be developed usingin situsoil as a surrogate for sediment characterization in these soils.

ISSN:0038-075X    

出版商:OVID    

年代:2003

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:2003

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:2003

数据来源: OVID