摘要:

Field experiments were established at two locations (on an Oxisol and an Ultisol) to evaluate the effects of 0, 8, 16, and 24 metric tons ha−1of aged municipal sewage sludge on soil properties and growth of four crop species. Soil samples taken from each plot, before sludge application and at harvest of the crops, are compared here to determine any effects of the sludge on pH, exchangeable acidity, exchangeable bases, cation and anion exchange capacity, and extractable phosphorus and trace metals. To test effects on soil properties in a more controlled environment, soil from one site was incubated with the sludge over a period of 4 months.No detrimental effects and several beneficial effects were observed. In particular, problems of soil acidity were diminished by an increase in pH and exchangeable calcium accompanied by a decrease in exchangeable acidity. Sludge applications also increased BaCl2-MgSO4CEC, but only in the Oxisol did the sum of cations increase. Dilute acid-fluoride extractable phosphorus also increased with sludge additions accounting for 2 to 19% of added sludge P for the Ultisol and 19 to 52% of P added to the Oxisol. Increases in Mehlich-3 extractable Cu and Zn in the soils were approximately equal to the amounts of these elements added to the soil in the sludge.

ISSN:0038-075X    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Two series of aluminum phosphate solutions were incubated at 90°C for 60 days to examine the processes of crystallization. Series A solutions were 0.05Min AlCI3, 0.15Min NaH2PO4, and had varying acidity ranging from HCl/Al molar ratio = 5 to NaOH/Al molar ratio = 3. Series B solutions were 0.001Min AlCl3, 0.0006Min NaH2PO4, and had a NaOH/Al molar ratio = 0 to 3. The nature of the reaction products was greatly affected by acidity and the concentrations of aluminum and phosphate. Variscite was observed only in Series A solutions of strong acidity. In a solution of HCl/Al molar ratio = 5 (pH 0.87), the reaction product was soluble aluminum phosphate complex. In solutions of HCl/Al = 2 (pH 1.36) to 3 (pH 1.17), well-crystallized variscite was observed at the very beginning of precipitation, with the amount and size increasing slowly with time. In solutions of NaOH/Al molar ratio = 2 (pH 3.29), the product was initially fine particles that were amorphous to X-ray diffraction, but gradually converted to variscite during incubation. In weakly acid solutions (NaOH/Al = 2.5 to 3.0; pH 5.2 to 6.0), the products remained X-ray-amorphous aluminum phosphates even after 60 days of incubation.No variscite was found in any sample from the Series B solutions. With increasing NaOH/Al ratio, the reaction products changed from soluble aluminum phosphate complexes to positively charged basic aluminum phosphate particles, then to a neutral precipitate, and finally to negatively charged particles. All precipitates or suspended particles were amorphous to X-ray diffraction and consisted of both OH−and PO43−linkages. These products did not show any tendency toward variscite crystallization up to at least 60 days. Solution concentrations 0.001Min Al and 0.0006Min P can be considered the upper limit of Al and P concentrations in ordinary soil solutions. Therefore, the conditions favorable for variscite formation are not compatible with those found in the ordinary soil environment.

ISSN:0038-075X    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Daily and accumulative water consumption of sandy, loamy, and clayey soils that had been amended by two negatively-charged organic polymers (Polyacryl-amide-PAM) applied at rates of 25,50, and 75 mg/kg of soil were studied in a growth chamber experiment. Water retention due to PAM application was either impaired or enhanced in sandy and loamy soils, respectively; clayey soil was significantly less affected. Plant root presence in the amended soils always had a corrective influence on soil structure and water retention over unamended soils.

ISSN:0038-075X    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Fertility trials for wheat (Triticum aestivum) were conducted in high (2,800 meters above sea level (masl)) and lower (2,300 masl) altitudes of the central high valley of Mexico. Check yields of wheat (i.e., without fertilizer) in the lower altitude zone were found to be correlated with soil organic matter (SOM) levels (r2= 0.79). This relationship broke down, however, when check yields from higher sites with higher levels of SOM were included. A greenhouse study suggested that the field results were due largely to a temperature effect on N mineralization. Sixty-nine sites were sampled and analyzed for a range of soil characteristics in order to identify the basis for different SOM levels and to establish whether the contribution of SOM to soil properties other than N varied with altitude or SOM level. The levels of SOM were related primarily to altitude (assumed to be a temperature effect) and less so to silt content. Despite the relatively large range in SOM levels (8-fold differences), the contribution of SOM from different altitudes and at different levels to cation exchange capacity (CEC), water availability, and equilibrium bulk density were similar. The effect of pH on CEC is stressed and the beneficial effects of SOM on a range of soil properties are quantified. Unknowns in respect to the ‘active’ fractions for various SOM effects are discussed.

ISSN:0038-075X    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Characterization of the growth of annual bluegrass (Poa annuaL.) and creeping bentgrass (Agrostis palustrisHuds.) over a broad range of pH and phosphate levels was needed to better investigate potential effects of soil acidity and P on annual blue-grass infestation in creeping bentgrass stands. Two acid soils were treated with varying rates of lime and P fertilizer. Clipping yields and P uptake of both grasses, as well as the levels of soil NaHCO3-extractable P and exchangeable Al, were all significantly related to lime and P treatments. High lime and high P treatments benefited annual bluegrass more than creeping bentgrass as revealed by clipping yields and P uptake. Lime invariably reduced the exchangeable soil Al with a small effect on NaHCO3-P levels in the lime rates used. The increased responses of clipping yields and P uptake to NaHCO3-P by liming could be attributed to the reduction of phytotoxic Al. The molar ratio of NaHCO3-P to exchangeable Al was a suitable parameter to describe the overall lime and P effects on the growth of either grass. High lime and high P applications which lead to high molar ratios of NaHCO3-P to exchangeable Al should be avoided in order to reduce the competition of annual blue-grass, particularly for soils that contain high organic matter and organic N. Further study is needed to elucidate the contribution of organic N mineralization to the differential growth behavior between the two grasses in the turf system.

ISSN:0038-075X    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Stages of carbonate accumulation are major indicators of soil age in many soils of arid and semiarid regions. The total amount of carbonate in these soils also has potential as a valuable tool for estimating the actual ages of specific soils and their landscapes. However, much more work is needed on factors that can affect the amount and distribution of carbonate in soils of the same age. A roadcut across a ridge in southern New Mexico exposed both stages I and II carbonate in soils of the Leasburg surface (early Holocene-latest Pleistocene). On the ridge crest, most soils have a stage I carbonate horizon characterized by faint coatings on grains. A ridge-crest Torripsamment in Leasburg sediments has a total of 28 kg/m2of pedogenic carbonate. On ridge sides, the steeper slopes have increased runoff, thus lifting the wetting fronts and the zone of carbonate accumulation, and most soils have a nodular stage II carbonate horizon. Although the ridge sides must be younger than the crest, they are thought to be only slightly younger because the stage II horizon is typical of Leasburg soils in nongravelly materials. A ridgeside Torriorthent in Leasburg sediments has a total of 46 kg/m2of carbonate. Thus in sandy soils of stable ridge crests, some carbonate apparently moves to substantial depths, causing anomalously low totals of carbonate for the soils concerned. For this reason, in chronological studies involving carbonate in sandy soils, long and deep exposures are required for a proper assessment of the stage of carbonate accumulation and the total amount of illuvial carbonate associated with soil development. Because a buried soil may be present, carbonate in the horizons concerned was not included in the totals of pedogenic carbonate, and the reported totals are, therefore, minimum values for soils of the Leasburg surface.

ISSN:0038-075X    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

An experiment was conducted to evaluate the effects of four rates of straw mulch on runoff, infiltration, and erosion at a site in northeastern Oregon. Straw mulch densities of 0, 25, 50, 75, and 100 percent cover were tested using simulated rainfall applied to 3.33 m2plots located on a 16 percent north facing slope. Soil type is a Thatuna silt loam (fine-silty, mixed mesic Xeric Argialboll). The zero cover plots were replicated four times. The mean rainfall input rate of 28 mm/h did not vary significantly over the four replications. Median drop diameter of 1.3 mm at the center of the spray pattern is a nominal design characteristic of the rainfall simulator and is a representative size for natural rainfall in this area. Percent straw cover and normalized soil loss were highly correlated (r= 0.99), while no significant correlation between runoff volume or infiltration volume and soil loss was observed. This can be explained by the presence of a slowly permeable layer below the tillage depth and by the high organic matter content of this soil. The data suggest that smaller amounts of mulch (<25%) are of little value in erosion control and that a threshold value below which surface cover is ineffective may exist. This is a significant departure from the exponential relationship used to determine straw mulch effects on erosion. The data from this and earlier, similar experiments exhibit a large variability, especially in the erosion component, and emphasize a need for more experimental data to define the cover-soil loss relationship. There is almost no experimental field data for mulch covers less than about 30 percent, so further research is urgently needed to define the relationship for these lower cover conditions.

ISSN:0038-075X    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Standard erosion plots, 4.6 m × 22.1 m with a 9% slope, were established at the Alston Surface Mine in Ohio County, Kentucky. Topsoil, subsoil, and mine spoil were reconstructed according to contemporary reclamation techniques using bulldozers and scraper pans. The following parameters were evaluated under natural rainfall conditions: runoff, erodibility, and sediment yield. Mine spoil yielded significantly greater runoff volumes, compared with reconstructed topsoil and subsoil. Average curve numbers (CN) were 89.1, 90.1, and 94.7 for bare topsoil, subsoil, and mine spoil, respectively. The subsoil plot generated the largest amount of sediment and was significantly more erodible than topsoil and mine spoil. The average annual erodibility (K) factor was .046 for topsoil, .067 for subsoil, and .051 for mine spoil, with units of Mg ha h (ha MJ mm)−1. Erodibility of the mine spoil in this study was more than twice that measured from an earlier rainfall simulation study at this same site. Differences in the degree of physical weathering were believed to be the primary contributing factor and, therefore, have important implications when assessing the erodibility of highly weathered spoil materials (e.g., abandoned mine lands). Compared with the soil interpretation record's K factor estimate for the soil series evaluated in this study, the reconstructed topsoil was not inherently more erodible than when existing in its natural, undisturbed condition. Therefore, factors that the mine operator can control (e.g., slope, vegetative cover, management practices) will likely have a greater impact on whether erosion losses from reconstructed soils are significantly greater than losses that occur under pre-mining conditions.

ISSN:0038-075X    

出版商:OVID    

年代:1993

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1993

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1993

数据来源: OVID