Showing papers on "Silt published in 2002"

Soil Organic Matter Dynamics in the Subhumid Agroecosystems of the Ethiopian Highlands

Abstract: We used natural 13 C abundance coupled with particle-size fractionation to evaluate soil organic carbon (SOC) dynamics following deforestation and subsequent cultivation in the subhumid Ethiopia highlands. Surface soil (0-10 cm), leaf, root, and litter samples were collected from natural forest and fields cultivated for 25 yr (Wushwush) and from Podocarpus dominated natural forest and 30 yr cultivated fields (Munesa) and C, N and δ 13 C signature were measured. Total SOC declined by 55% (32.0 Mg ha -1 ) at Wushwush and by 63% (40.2 Mg ha -1 ) at Munesa following cultivation, while losses of N amounted to 52% (2.8 Mg ha -1 ) and 60% (3.1 Mg ha -1 ) at the two sites, respectively. δ 13 C values of bulk soils of natural forests at Wushwush (-24.3‰) and Munesa (-23.4‰) were significantly lower than those from the corresponding cultivated fields (-19.9‰, Wushwush and -15.5‰, Munesa). Deforestation and continuous cultivation at Wushwush and Munesa resulted in depletion of 80 and 96% of the initial forest-derived SOC in sand, while 73 and 85% of C 3 SOC was lost from silt fraction of the two sites, respectively. These results suggest that SOC in sand was a very labile component of SOM and is a more sensitive indicator to changes in soil C storage in response to land use changes. However, the substantial amount of forest-derived SOC lost from silt indicates that SOM associated with silt was also quite susceptible to management changes, and that at least in the soils under study represents a moderately labile SOM pool, which is generally not the case in temperate soils. Forest-derived SOC in clay declined by 48 and 61% at Wushwush and Munesa, respectively, suggesting that clay retained C 3 derived SOC more effectively and that SOM bound to clay was more stable than SOM associated with sand and silt fractions.

Silt fences: An economical technique for measuring hillslope soil erosion

Abstract: Measuring hillslope erosion has historically been a costly, time-consuming practice. An easy to install low-cost technique using silt fences (geotextile fabric) and tipping bucket rain gauges to measure onsite hillslope erosion was developed and tested. Equipment requirements, installation procedures, statistical design, and analysis methods for measuring hillslope erosion are discussed. The use of silt fences is versatile; various plot sizes can be used to measure hillslope erosion in different settings and to determine effectiveness of various treatments or practices. Silt fences are installed by making a sediment trap facing upslope such that runoff cannot go around the ends of the silt fence. The silt fence is folded to form a pocket for the sediment to settle on and reduce the possibility of sediment undermining the silt fence. Cleaning out and weighing the accumulated sediment in the field can be accomplished with a portable hanging or platform scale at various time intervals depending on the necessary degree of detail in the measurement of erosion (that is, after every storm, quarterly, or seasonally). Silt fences combined with a tipping bucket rain gauge provide an easy, low-cost method to quantify precipitation/hillslope erosion relationships. Trap efficiency of the silt fences are greater that 90 percent efficient, thus making them suitable to estimate hillslope erosion. Keywords—silt fence, erosion, erosion rate, sediment, measurement techniques, monitoring

Particle-Scale Understanding of the Bioavailability of PAHs in Sediment

Abstract: This study reports results of sediment bioslurry treatment and earthworm bioaccumulation for polycyclic aromatic hydrocarbon (PAH) contaminants found in sediment dredged from Milwaukee Harbor. A significant finding was that bioslurry treatment reduced PAHs on the sediment clay/silt fraction but not on the sediment coal-derived fraction and that PAH reduction in the clay/silt fraction correlated with substantial reduction in earthworm PAH bioaccumulation. These findings are used to infer PAH bioavailability from characterization of particle-scale PAH distribution, association, and binding among the principal particle fractions in the sediment. The results are consistent with work showing that the sediment comprised two principal particle classes for PAHs, coal-derived and clay/silt, each having much different PAH levels, release rates, and desorption activation energies. PAH sorption on coal-derived particles is associated with minimal biodegradation, slow release rates, and high desorption activation ener...

Flow–sediment–biota relations: implications for river regulation effects on native fish abundance

Abstract: Alteration of natural flow regimes by river regulation affects fish distribution and assemblage structure, but causative pathways are not always direct and may go un- recognized. The Colorado River population of the endangered Colorado pikeminnow, Ptych- ocheilus lucius, suffers from low rates of recruitment and reduced carrying capacity. We hypothesized that availability of prey fish for this large-bodied native piscivore may, in part, be limited by reduced standing crops of periphyton and macroinvertebrates resulting from accumulation of fine sediment in the riverbed. We stratified the 373-km-long study area into 11 strata and sampled various physical and biological parameters in runs and riffles of three randomly selected 1- to 3-km-long study reaches in each stratum during base flows of spring and fall 1994-1995. Significant correlations were found between biomass of both chlorophyll a and macroinvertebrates and various physical metrics that described the degree of fine sediment accumulation in gravel-cobble substrates. Riffles were relatively free of fine sediment throughout the study area, but substrates of runs contained progressively more fine sediments with distance downstream. There was a cor- responding longitudinal change in biota along the river continuum with greatest biomass of fish, invertebrates, and periphyton upstream. Adult pikeminnow were concentrated in upstream strata where potential prey fishes were most abundant. We suggest that fine- sediment effects on biota have increased in recent years as a result of river regulation. Historically, spring snowmelt frequently produced flows with magnitudes sufficient to mo- bilize the bed and winnow silt and sand from coarse substrates. Following regulation, the mean recurrence interval of such flows lengthened from 1.3-2.7 yr (depending on the stratum) to 2.7-13.5 yr, extending the duration of fine sediment accumulation and potentially depressing biotic production. Our results describe and help explain the spatial distribution of the Colorado River fish community and establish a link between flow, sediment, and the riverine food web supporting the community's top predator. To maintain intact native fish communities in this and other river basins, managers need to identify functional aspects of the natural hydrograph and incorporate these findings into river restoration efforts.

Hydrogeochemistry and cation-exchange processes in the coastal aquifer of Mar Del Plata, Argentina

Abstract: The aquifer of Mar del Plata is unconfined and composed of silt and fine sand. The sand fraction is mainly quartz, potassium feldspars, chalcedony, and gypsum. Volcanic-glass shards (40–60%) dominate the silt fraction, and the clays are of the smectite and illite groups. Calcium carbonate, in caliche form, constitutes about 10–20% of the sediment.

Mineralogy and sedimentology of pleistocene sediment in the south china sea (odp site 1144)

Abstract: Grain size, detrital mineral, clay mineralogy (<2 μm), and major element analyses were carried out on the carbonate-free fraction of sediments from Ocean Drilling Program Site 1144 from the northern margin of the South China Sea (SCS), close to the mouth of the Pearl River. This site provides a 517-m sedimentary record extending back to 1.1 Ma. Clay content and the chemical index of alteration do not exhibit significant variation between glacial and interglacial changes, suggesting no important change in the proportion of primary to secondary minerals in the sediment. Two grain size populations were identified, 2.5–5 μm (clay) and 20–40 μm (silt). Glacial stages are characterized by higher proportions of silt size and quartz content than interglacial stages. Two hypotheses can explain these variations: (1) drier conditions associated with an intensification of winter monsoon transport of eolian loess to the northern part of the SCS during glacial periods and/ or (2) an effect of sea level changes on the detrital material transport from continent or shelf to the deep ocean.

Measurement of Attenuation and Speed of Sound in Soils

Abstract: The potential application of this work is the detection and imaging of buried objects using acoustic methodology. To image buried artifacts, it is vital to know speed and attenuation of sound in the particular soil being examined because they vary in different soil types and at different moisture contents. To that end, our research involved six soils representing a range of properties expected to influence acoustic response. Clay ranged from 2 to 38%, silt from 1 to 82%, sand from 2 to 97%, and organic matter from 0.1 to 11.7%. Signals from an acoustic source were passed through soil samples and detected by an acoustically coupled hydrophone. From a total of 231 evaluations, we determined the acoustic attenuation coefficient and the propagation speed of sound in the soil samples as a function of four levels of soil moisture and two levels of compaction. Attenuation coefficients determined over frequencies of 2 to 6 kHz ranged from 0.12 to 0.96 dB cm -1 kHz -1 . Lower attenuation tended to be in loose dry samples. Correlation coefficients were 0.35 (P = 0.01) and 0.31 (P = 0.03) between attenuation and soil water content and soil bulk density, respectively. Propagation speeds ranged from 86 to 260 m s -1 . The correlation coefficient with speed was -0.28 (P = 0.05) for soil water content and -0.42 (P = 0.002) for total porosity. Given the acoustic properties, it is theoretically possible to detect an object down to ∼40 cm below the soil surface.

Strength and dilatancy of a silt stabilized by a cement and fly ash mixture

Abstract: The mechanical behaviour of a weakly cemented silt was studied experimentally. The cementing agent was a cement and fly ash slurry, and the samples so formed were slightly cemented. In triaxial tes...

Enumeration of faecal coliforms from recreational coastal sites: evaluation of techniques for the separation of bacteria from sediments.

Abstract: D . L . C R A I G , H . J . F A L L O W F I E L D A N D N . J . C R O M A R . 2002. Aims: To identify the most efficient techniques for the separation of micro-organisms from coastal sediments and, using these techniques, to determine the concentration of faecal indicator organisms in recreational coastal water and sediment. Methods and Results: Sediment samples were taken from a range of recreational coastal sites and subjected to various physical techniques to separate micro-organisms from sediment particles. Techniques investigated included manual shaking, treatment by sonication bath for 6 and 10 min, respectively, and by sonication probe for 15 s and 1 min, respectively. The use of the sonication bath for 10 min was the most successful method for removing microorganisms from sediment particles where sediments consisted mainly of sand. When sediments contained considerable proportions of silt and clay, however, manual shaking was most successful. Faecal coliforms were then enumerated by membrane filtration in both water and sediment from three recreational coastal sites, chosen to represent different physical sediment characteristics, over a 12-month period. Faecal coliform concentrations were generally greater in sediment compared with overlying water for all samples. This was most evident in sediment consisting of greater silt ⁄ clay and organic carbon content. Conclusions: This study demonstrated the importance of sediment characteristics in determining the most efficient method for the separation of micro-organisms from coastal sediments. Sediment characteristics were also found to influence the persistence of microorganisms in coastal areas. Significance and Impact of the Study: Recreational coastal sediments can act as a reservoir for faecal coliforms; therefore, sampling only overlying water may greatly underestimate the risk of exposure to potentially pathogenic micro-organisms in recreational waters.

Influence of prolonged arable cropping on lignin compounds in sandy soils of the South African Highveld

Abstract: Summary The preservation of plant residues is important for sustainable arable cropping. Lignin is a marker for plant residues in soils. We have investigated influences of the length of cultivation on the dynamics of lignin. Composite samples were taken from the top 20 cm of soils that have been cropped for periods varying from 0 to 98 years in each of three different agro-ecosystems in the Free State Province of South Africa. Lignin-derived phenols were determined in the <2 µm (clay), 2–20 µm (silt), 20–250 µm (fine sand) and 250– 2000 µm (coarse sand) size separates. With increasing length of cultivation, the concentration of such phenols decreased to 36% of that in the grassland. The lignin contents as proportions of the total carbon did not change during cultivation, suggesting that there was no selective enrichment of lignin moieties as C was lost as a result of cultivation. The loss rate constants of lignin concentrations in particle-size fractions increased in the order clay (0.17 year−1) ≤ silt (0.18 year−1) < fine sand (0.20 year−1) < coarse sand (0.22 year−1). Increasing ratios of phenolic acids to aldehydes in bulk soil, silt and fine sand fractions with increasing length of cultivation indicated that side chains were being oxidized. The ratios in the silt fraction, however, decreased after 10–20 years. We attribute this to a loss of lignin together with silt by wind erosion, resulting in a rejuvenation of lignin compounds in the remaining silt-sized pools of C.

ISRIC-WISE global data set of derived soil properties on a 0.5 by 0.5 degree grid (ver. 3.0)

Abstract: This harmonized, gridded global data set of soil parameter estimates includes files listing: (1) soil parameter estimates for the component soil units of each terrestrial grid cell, in un-binned format, and (2) soil parameter estimates aggregated or binned into a number of predefined classes. The spatial data, with a resolution of ½ by ½ degree, was derived from the ISRIC-WISE soil database. The land surface between longitudes -180o W and +180o E and latitudes +90o N and -90o S has been characterized using 45948 unique map units; each of these can comprise from one to ten soil units, characterized according to the original legend of the 1:5 million scale Soil Map of the World (FAO-Unesco 1974). Soil parameter estimates for each of these units were derived from analyses of some 9600 profiles held in a working copy of WISE (ver. 2.0). Twenty-two soil variables, identified as being useful for agro-ecological zoning, land evaluation, crop growth simulation, modelling of soil gaseous emissions and analyses of global environmental change, were considered. Parameter estimates for the topsoil (0-30 cm) and the subsoil (30-100 cm) are presented for the following variables: content of organic carbon, total nitrogen, the C/N ratio, pH(H2O), CECsoil, CECclay, base saturation, total exchangeable bases, aluminum saturation, exchangeable sodium percentage (ESP), electrical conductivity of saturated paste (ECe), calcium carbonate content, gypsum content, content of sand, silt and clay, content of fragments > 2 mm, bulk density, total porosity. For soil drainage class, effective soil depth, and available water capacity (-10 to -1500 kPa), however, parameter estimates are presented on a profile basis. The parameter estimates - median values - presented here should be seen as best estimates; possible types and sources of uncertainty are discussed in the report. The data are considered appropriate for exploratory studies at global scale (< 1:5 000 000).

Cryptosporidium parvum oocyst inactivation in three soil types at various temperatures and water potentials

Abstract: The interaction between soil types, temperature, and soil water potential may have differential effects on the survival of Cryptosporidium parvum oocysts in the terrestrial environment. We examined the effects of three soil types (a silty clay loam, silt loam, and loamy sand), three temperatures (4, 20, and 30 °C), and three soil water potentials (−0.033, −0.5 and −1.5 MPa) on the inactivation kinetics of oocysts. Sentinel chambers were filled with air-dried and sieved soil, brought to the appropriate soil water potential, and inoculated with 2×106 freshly purified oocysts. The inoculated chambers were buried in the same bulk soil at the appropriate water potentials and incubated at one of the three temperatures. Triplicate chambers were removed from the bulk soil on days 0, 22, 43, 84 and 156. Sentinel oocysts were extracted, and assayed for potential infectivity by the dye permeability method. Oocysts suspended in sterile distilled water and incubated with the sentinel chambers were used as controls for the effect of temperature. The soil water potentials investigated did not affect oocyst inactivation at any temperature or with any of the three soil types. Rates of oocyst inactivation increased significantly between 4 and 20 °C, but not between 20 and 30 °C with the exception of oocysts incubated in the silty clay loam. Oocyst survival appeared to be significantly greater in the silt loam soil than in the two other soil types when incubated at 20 °C; and at 30 °C oocyst survival was significantly less in the silt clay loam than in the other two soil types. Rates of sentinel oocyst inactivation at all three soil water potentials were significantly lower than the control oocysts in water at the three test temperatures. Thus oocyst survival in soil was not affected by the water potentials between −0.033 and −1.5 MPa; it was affected by soil texture; but temperature appeared to be the factor most affecting oocyst survival. In the critical ambient range of temperature in temperate climates oocysts may survive for months in agricultural soil, and pose a threat to surface waters.

Sorption Strength of Persistent Organic Pollutants in Particle-size Fractions of Urban Soils

Abstract: The bioavailability of persistent organic pollutants in soils depends on their sorption strength that may vary among different pools. We hypothesized that polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) had different soil organic C-water partition coefficients (K OC ) among particle-size fractions. We determined the concentrations of 20 PAHs and 12 PCBs in coarse-sand, fine-sand, silt, and clay fractions of 11 urban topsoils (0-5 cm). The K OC values were determined using sequential extraction with methanol-water mixtures (35 and 65% methanol) at 60°C. The 220 PAHs concentrations ranged from 0.3 to 186 mg kg -1 , the Σ12 PCBs concentrations from 1.2 to 158 μg kg -1 . In most soils, the PAH concentrations decreased in the order, silt > clay ≥ fine sand > coarse sand, and those of the PCBs in the order, clay > silt ≥ fine sand > coarse sand. The distribution of PAHs among particle-size fractions was more heterogeneous than reported in the literature because the soils received PAH-contaminated wastes (ashes, slags, rubble) with varying texture. In all soils, the proportions of two- or three-ring PAHs decreased with decreasing particle size, indicating that the PAH mixture was increasingly altered. The K OC values of the PAHs were three to 10 times higher than those of the PCBs with similar octanol-water partition coefficients (K OW ). The mean K OC values of all individual PAHs were highest in silt. For all individual PCBs, mean K OC values were highest in clay. The K OC values of PAHs and PCBs varied up to a factor of 100 among the studied soils and particle-size fractions. Particle-size fractions with highest PAH and PCB concentrations also showed highest K OC values indicating low bioavailability.

A paleohydrologic reinterpretation of the Homeb Silts, Kuiseb River, central Namib Desert (Namibia) and paleoclimatic implications

Abstract: Slack water deposits are usually fine-grained (fine sand and coarse silt) flood sediments deposited in areas of the floodplain that are sheltered from high-velocity flood flows. Slack water deposits have been recognized by many investigators in a wide variety of physiographic and climatic settings. Late Quaternary slack water deposits have not been described from the extremely arid Namib Desert of southwestern Africa. Fine-grained flood sediments in the Kuiseb Valley near Homeb, accumulated between 23,000 and 19,000 14C-years BP, have been interpreted by previous workers as (i) sediments deposited behind dune dams, (ii) river endpoint accumulations, and (iii) flood deposits of an aggrading river controlled either by a base level change in the lower reaches or a change in the hydrological regime in the catchment area. Furthermore, the so-called Homeb Silts could document more arid climatic conditions in the Kuiseb catchment area during the last glacial maximum (LGM). Our research shows that the Homeb Silts are slack water deposits and that in many valleys of the Namib Desert, slack water sediments are observed most commonly at the junctions of major rivers and minor tributaries in bedrock canyon settings. Here we present evidence that these slack water deposits accumulated as a result of more humid conditions and/or more intense precipitation events in the upper reaches of the river. They do not document climatic changes in the desert itself as postulated by many researchers.

Mineralogy of soils with unusually high exchangeable Al from the western Amazon Region

Abstract: Some soils from the western Amazon region contain KCl-extractable Al contents 5 to 10 times greater than is typical for highly weathered soils containing predominantly kaolinite and gibbsite. We studied a soil sequence from the Brazilian western Amazon consisting of two Typic Udifluvents on the levee of the Javari River, one Aeric Endoaquent in the backswamp, and two Typic Hapludults on an adjacent terrace. We used wet chemical and X-ray diffraction (XRD) analysis to characterize several size fractions of the 0 to 0.2 m layer of the soils. The exchangeable Al content was very high in the Aquent and Udults (up to 180 mmol c kg -1 ), but the 'total' Fe content was low in all samples (<60 g kg -1 ). Smectite, vermiculite, hydroxy-interlayered smectite and kaolinite dominate the fine silt and clay fractions of all soils. The Fluvents contain illite in all size fractions and chlorite in the coarse clay and fine silt fractions. The Aquent and Udults have no chlorite, and small amounts of illite occur only in the coarse clay and fine silt fractions. Lepidocrocite was identified in the Aquent. Chlorite, which occurs in the sand, fine silt, and coarse clay fractions of the Fluvents, and pyrophyllite, which occurs in the fine silt fractions of all soils and in the coarse clay of the two Ultisols, appears to be inherited from the parent sediments. The hydroxy-interlayered 2:1 phyllosilicates that form as a result of weathering are the cause of the very high exchangeable Al contents.

Phosphorus in Bottom Sediments of Pomeranian Bay (Southern Baltic—Poland)

Abstract: The paper presents the results of determination of inorganic and organic forms of phosphorus in bottom sediments of Pomeranian Bay. The sediments were collected in March and July of 1996. The following characteristics of the sediments were determined: organic matter content, forms of inorganic phosphorus: loosely adsorbed phosphorus and phosphorus bound to aluminium, calcium and iron, as well as total inorganic phosphorus. Pomeranian Bay is a shallow basin, with depth averaging between 12 and 15 m and sandy sediments prevailing. Smaller silt fractions occur only in the vicinity of the Świna River estuary and in deeper northern regions of the Bay. Calcium-bound phosphorus is the dominant form of inorganic phosphorus in the Pomeranian Bay. Iron-bound phosphorus is the second most prevailing form, and aluminium-bound phosphorus the third. Loosely bound phosphorus was present in the lowest amounts. Total inorganic phosphorus in the Bay consisted of the four forms listed above, except in estuarine regions where an additional form of phosphorus occurred, most probably occluded phosphorus. High organic phosphorus concentrations were found at the Świna River estuary and in the northern part of the Bay (Sasnitz Deep) corresponding to the higher organic matter content of these sediments. Sediments of Pomeranian Bay contained less phosphorus than those from the Gulf of Gdansk or Puck Bay and other parts of the Baltic Sea, suggesting that the amount of phosphorus in the sediments was determined by a number of inter-related factors, such as sediment type, amount of organic matter, the chemical composition of the sediment and oxygen content of near-bottom water.

Elemental geochemistry of wind-erodible playa sediments, Owens Lake, California

Abstract: Wind erosion of the dried bed (playa) of Owens Lake, California is an extremely intense source of mineral aerosol, transporting dust hundreds of kilometers downwind to critical ecological areas and several cities. A dust-producing site on the playa was studied over a four-year period to document the processes associated with aerosol emission. The playa takes on a variety of sedimentary forms and phases with surface crusts of differing susceptibilities to wind erosion. The sediments are classed into three general categories based on appearance: soft (saline), loose with drifting sand (salt–silt–clay), and hard and clean (silt–clay). Sediment samples were collected over a two-year period as the study site cycled through all three crust types, and the samples were crushed and analyzed by PIXE. The results indicate that visual appearance and sedimentary structure does not correlate with elemental composition. All sediment types contain significant concentrations of various elements including sodium, calcium and silicon. Potentially toxic trace elements are also found in the sediments. All sediment types contain lead and/or arsenic in tens of parts per million, as well as various other heavy metals. Pb and As levels do not clearly correlate with salt content or sediment type. Arsenic levels may be slightly higher in the crusts with loose material present and potentially lower in the clean hard crusts, while Pb was least frequently detected in the samples with loose material. Future research will add mineralogical and stable isotope analyses to correlate with the PIXE data.

Sediment properties along gradients of siltation in south-east Asia

Abstract: Marine sediment properties were quantified along SE Asian siltation gradients and across different habitat types to assess the extent of terrestrial sediment influence and derive indicators of of terrestrial sediment input. Three sites in the Andaman Sea (Ranong, Phuket and Trang; Thailand), one site in the Gulf of Thailand (Pak Phanang; Thailand) and three sites in the South China Sea (Bolinao at the Luzon Island, Puerto Galera at the Mindoro Island and El Nido at the Palawan Island, all in the Philippines) were studied. The following main habitat types were covered: mangroves, seagrass beds, coral reefs, mud flats, river mouths and deep channels. Particularly in Bolinao and El Nido, distinct fronts in siltation were identified at about 7 km from the source. Mud ( 250 m), total and inorganic carbon as well as calcium. Interstitial ammonia and phosphate varied with the fine sand fraction along the second axis. Two-way analysis of variance showed that water depth, distance from silt source, site and habitat type all contributed to the variance, but site explained most. Linear regressions showed positive correlations between silt and water content, organic matter, total nitrogen, total phosphorus and iron, but negative correlations with calcium suggesting iron and calcium as markers for terrigeneous and marine origin, respectively. The composition of the sediment particulate matter groups the habitat types in two clusters: (1) silty types as river mouths, shallow mud bottoms, deep channels and mangrove stands with high contents of organic matter and nutrients versus (2) non-silty types as seagrass beds and coral reefs with low contents of nutrients and organic matter. Median settling velocities of the silt loads varied from 0·6 m d 1 to 27 m d 1 . Experimentally determined susceptibility to resuspension identified a critical water content of 50%. 2002 Elsevier Science Ltd.

Relating Potato Yield and Quality to Field Scale Variability in Soil Characteristics

Abstract: Causes of within-field spatial variability in potato (Solarium tuberosum L.) yield are not well understood. To address this, a study was conducted from 1998 to 2000 on a commercial farm in southeastern Washington. Soil samples were collected from four center-pivot-irrigated, uniformly fertilized fields on a 0.4-ha grid interval prior to potato planting and analyzed for nitrate-N, ammonium-N, P, K, organic matter, pH, and texture. The elevation of each grid point was also recorded. Four to five days before commercial harvest, potatoes were collected from a 3-m row length at each original grid point using a one-row digger. The potatoes were weighed, sorted into five weight classes, and evaluated for specific gravity. Correlation and stepwise regression analyses were conducted to test relationships between soil-based and yield variables. Factors driving yield varied between fields. Soil texture components (sand, silt, clay) had stronger impact on yield than with the soil chemical properties we measured. However, all four fields showed an inverse relationship between specific gravity and soil test K, although the correlation coefficients and contributions to regression models were relatively low. Finding a general prescription formula for goals other than higher yield (e.g., nutrient-leaching potential) may be feasible. The consistent relationship of soil textural components in our models suggest that monitoring available soil water, a factor closely related to soil texture, should be included in any future work.