Typic Hapludult Research Articles

Using Soil Phosphorus Profile Data to Assess Phosphorus Leaching Potential in Manured Soils

Transport of P by subsurface flow pathways can be an important mechanism of P transfer from land to water, particularly in manured soils that are artificially drained. This study was conducted to determine whether detailed description and interpretation of soil P profile data provide adequate insight into P leaching potential. Evidence of P translocation within soil profiles of a tile‐drained Buchanan (fine‐loamy, mixed, semiactive, mesic Aquic Fragiudult)‐Hartleton (loamy‐skeletal, mixed, active, mesic Typic Hapludults) catena was assessed by measuring oxalate‐extractable P, P sorption saturation, Mehlich‐3 P, water‐extractable P in bulk and clay film samples obtained from individual horizons. Tile‐drain monitoring and column leaching experiments were conducted to evaluate interpretations derived from soil P profile data. Soil P fractions were not correlated with P losses in lysimeter studies, indicating the limited potential of using soil profile P data for quantitative prediction of leaching losses. Application of manure to the soil surface resulted in significant increases in leachate P concentrations from the lysimeters. Soil profile P data did, however, provide some evidence of long‐term P leaching. While bulk horizon samples did not indicate significant long‐term P translocation to soil depths corresponding with artificial drainage, some clay film samples had significantly elevated oxalate P, P sorption saturation and Mehlich‐3 P at lower depths. Elevated P concentrations in clay films may be associated with preferential transport of P along soil macropores, although, not all clay films sampled in this study were necessarily associated with active macropores. Thus, soil P profile data appear to provide limited insight into P leaching potential.

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

AbstractSome 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 mmolc 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.

Mineralogy of eroded sediments derived from highly weathered Ultisols of central Alabama

Coarse-textured surface horizons are common in highly weathered southeastern US coastal plain soils. These soils have historically been managed under conventional tillage practices, but conservation tillage management practices are increasing. Although clay (<2 μm) contents are low in these surface horizons (typically <100 g kg −1), the reactive nature of this fraction tends to play a dominant role in colloidal facilitated pollutant transport. Studies have suggested that enrichment of certain minerals occurs in transported sediments, thus, we evaluated sediment size and the mineralogical partitioning of clay minerals of soil versus runoff sediment under simulated rainfall. In addition, because water dispersible clay (WDC) has been shown to be correlated with soil erodibility, we evaluated WDC differences as a function of tillage practices. Plots were established at a site in the upper coastal plain of central Alabama, where soils classified as coarse-loamy, siliceous, subactive, thermic Plinthic Paleudults and Typic Hapludults (FAO-Acrisols). Surface tillage treatments were established in 1988, and included conventional tillage (CT) versus no surface tillage (NT) treatments, with crop residue remaining or removed, and with or without paratilling (non-inversion subsoiling). Within these plots, simulated rainfall (target intensity=50 mm h −1 for 2 h) was applied to replicated 1 m×1 m areas, and runoff and sediment were collected. Mineralogical analyses of soils and sediment were conducted using thermogravimetric analysis (TGA) and X-ray diffraction (XRD) techniques. WDC quantities were highly correlated with percent soil organic carbon (SOC) ( r 2=0.76), which was a function of tillage treatment. Although no differences in the mineralogy of the <2 μm sediment were observed between tillage treatments, runoff sediments (<2 μm) were enriched in quartz (qtz) and relatively depleted with kaolinite compared to in situ soils. These findings will facilitate development of mechanistic models that predict sediment attached losses of nutrients and pesticides.

Effects of Lime and Calcium on Root Development and Nodulation of Clovers

Acidic soils can reduce the nodulation of forage legumes. Studies with a Gilpin series silt loam (fine loamy, mixed mesic, Typic Hapludult) from New, WV, were conducted to determine the effects of lime on root development, and to assess effects of soil Ca and pH on nodulation. Liming increased soil pH from 4.8 to 5.3, nodulation, and root growth of white clover (Trifolium repens L., cultivar Huia) 28 d after planting. Seedlings from unlimed soil formed fewer indeterminate and determinate roots. Next, soils were amended with either CaCO3 or a mixture of CaCO3 and CaSO4 to achieve a soil pH of 4.7 to 6.1 and soil Ca of 170 to 680 mg kg−1 soil. There was a strong quadratic relationship between number of nodules per white clover seedling 28 d after planting and soil pH. Another experiment was conducted to determine if these trends were expressed under field conditions. In 1993, field plots were amended with lime or a coal combustion by-product that supplied Ca as CaSO4 and seeded in 1994 to cool-season grasses. In spring of 1998, plots were drilled with either red (Trifolium pratense, L.) or white clover. The nodules per primary root were determined in May (1998, 1999) and August (1998). Number of nodules per primary root was more closely associated with soil pH than soil Ca. These results indicate that changes in nodulation were more closely associated with changes in soil pH than soil Ca.

Nutritive Value and Animal Selection of Forage Chicory Cultivars Grown in Central Appalachia

The unequivocal success of ‘Grasslands Puna’ (Puna) chicory (Cichorium intybus L.) as a forage species in other areas has not been realized in the central Appalachian Region of the USA. A field study was conducted in southern West Virginia (38° N, 81° W; 850 m above sea level) to compare nutritional qualities and palatability of herbage from three forage chicory cultivars that were developed in different parts of the world. Puna, ‘INIA Le Lacerta’ (Lacerta), and ‘Forage Feast’ were established on a Gilpin soil (fine‐loamy, mixed, semiactive, mesic, Typic Hapludults) in replicated plots in 1997 and 1998, and herbage was used for chemical analyses and ruminant feeding assessments. Whitetail deer (Odocoileus virginianus), in a free‐foraging situation, and sheep (Ovis aries), in two cafeteria trials, discriminated against Forage Feast. Deer selected Lacerta first; sheep did not exhibit a preference for Lacerta over Puna. Mature leaves from vegetative rosettes of the three cultivars had similar concentrations of crude protein, neutral detergent fiber, and acid detergent fiber (P &gt; 0.10). In vitro organic matter disappearance and amino acid composition were also similar among the cultivars (P &gt; 0.05). In all cultivars, approximately 65% of the total N occurred as protein amino acids. Nonprotein amino acids were not major constituents in any of the cultivars. Results suggest that differences in palatability and intake of chicory are related to the secondary plant metabolite composition of the herbage.

DIFFERENCES AMONG MYCORRHIZAL FUNGI FOR MINERAL UPTAKE PER ROOT LENGTH OF SWITCHGRASS GROWN IN ACIDIC SOIL

ABSTRACT Plants commonly encounter deficient and/or toxic levels of mineral elements when grown in acidic soil, and arbuscular mycorrhizal fungi (AMF) have potential to overcome many of these effects. Switchgrass (Panicum virgatum L.) was grown in acidic Lily soil (Typic Hapludult) at pHCa 4 and 5 (soil:10 mM CaCl2, 1 :emsp14;1) and inoculated with Glomus (G.) clarum, G. diaphanum, G. etunicatum, G. intraradices, Gigaspora (Gi.) albida, Gi. margarita, Gi. rosea, and Acaulospora (A.) morrowiae to determine differences among mycorrhizal (AM) plants for mineral uptake per root length (RL). Shoots of AM plants grown in pHCa 4 and 5 soil had extensive mineral nutrient content (per plant) differences, and AM plants grown in pHCa 4 soil generally had higher and wider ranges of mineral contents than plants grown in pHCa 5 soil. Mineral uptake per RL varied extensively among AM plants. The AM plants generally enhanced uptake of phosphorus (P), nitrogen (N), sulfur (S), potassium (K), calcium (Ca), magnesium (Mg), zinc (Zn), and copper (Cu) and reduced uptake of manganese (Mn), iron (Fe), boron (B), and aluminum (Al). The G. etunicatum plants particularly had higher P, N, S, K, Mg, Zn, and Cu uptake compared to the other AM plants. Most AMF isolates used were effective in enhancing mineral uptake and reducing excess amounts of toxic elements in shoots.

Limestone, Gypsum, and Magnesium Oxide Influence Restoration of an Abandoned Appalachian Pasture

When restoring abandoned pastures on acidic hill‐land soils to productivity, it is important to bring soil Ca and Mg to adequate levels. Gypsum is a readily available Ca amendment that is sufficiently soluble to move rapidly into the soil when surface‐applied. Gypsum has been shown to reduce detrimental effects of subsurface acidity in soils of the southeastern USA. A 4‐yr experiment was initiated to measure effects of surface gypsum application on forage production and to evaluate Mg‐containing amendments to avoid gypsum‐induced Mg deficiency. The study site was a southern West Virginia Gilpin silt loam (fine‐loamy, mixed, mesic, Typic Hapludult) where abandoned hill‐land pasture was being restored to productivity. Treatments included 0, 1000, 8000, 16 000, and 32 000 kg/ha flue gas desulfurization coal combustion by‐product gypsum (gypsum) together with dolomitic limestone and five additional treatments to evaluate sources of supplemental Mg. Application of 16000 kg/ha gypsum together with limestone increased forage yields of mixed orchardgrass (Dactylis glomerataL.) and tall fescue (Festuca arundinaceaSchreb) pasture during establishment by 42% and production by 11% compared with limestone alone. About 8% of the mean 790 kg/ha yield increase could be attributed to acidity‐neutralizing effects of alkaline constituents in the gypsum by‐product. Plants in higher gypsum treatments had higher concentrations of K and P, but gypsum application decreased soil and plant Mg concentrations. This indicated that gypsum should not be applied on typical acid soils without supplemental Mg.

No‐Till Corn Yields and Water Balance in the Mid‐Atlantic Coastal Plain

Water is the main limiting factor to rainfed corn (Zea mays L.) yield in the mid‐Atlantic coastal plain. This study was conducted to determine the water balance, yields, and efficiency of water use (EWU) of no‐till rainfed corn grown on three soils of varying water‐holding capacity, a Wickham sandy loam (fine‐loamy, mixed, thermic, Typic Hapludults) and two Bojac soils, a sandy loam and a loamy sand (coarse‐loamy, mixed, thermic, Typic Hapludults). Soil water balance was determined from climate data and weekly measurements of soil moisture from time domain reflectometry (TDR) probes. Water balance components of water stress, crop coefficients, and evapotranspiration were determined for vegetative, tasseling, and grain‐fill growth stages in 1998 and 1999. Yields were determined by overlaying georeferenced yield maps, order‐1 soil survey maps, and locations of TDR probes. The EWU concept was defined as yield divided by [precipitation + (initial soil water content − final water content)], clarifying it from water use efficiency measurements that are calculated similarly but do not include drainage. Yields in 1998 (4833–12200 kg ha−1) were higher than 1999 yields (2245–8240 kg ha−1) due to higher growing season precipitation in 1998 (400 mm) than 1999 (220 mm). Drainage was determined in 1998, ranging from 65 to 105 mm. Minimizing drainage losses has potential for increasing the EWU and yields. This study establishes baseline water balance data for the mid‐Atlantic coastal plain that can be used to parameterize computer models for investigating the effect of management practices on EWU and yields.

Eastern Gamagrass Root Penetration in Adverse Subsoil Conditions

Eastern gamagrass [Tripsacum dactyloides (L.) L] (EG) is reported to exhibit acid tolerance and root penetration through claypans. To study its root growth in these conditions, a greenhouse column study was conducted under simulated soil stress conditions, using EG and sordan [Sorghum × drummondii (Steud.) Millsp. &amp; Chase] as a comparison species. Treatments consisted of incomplete factorial combinations of plant species (EG and sordan), soil water potential (−10 and –300 kPa), lime (pH 3.5 and 4.8), and soil bulk density (Db) (1.3 and 1.7 g cm−3). The treatments were arranged as a randomized complete block design (RCBD). For some of the response variables that were analyzed at different depths, depth was considered as a subplot factor. Treatments were applied to Al‐toxic Tatum Bt horizon material (clayey, fine, mixed, semiactive, thermic Typic Hapludults) used in the middle 30‐cm section of 15 by 60‐cm polyvinyl Cl (PVC) columns. Soil strength was determined at harvest by cone penetrometer resistance. Results indicated that EG tolerated acid, Al‐toxic conditions, while sordan roots were sensitive to the low pH conditions. Eastern gamagrass roots penetrated high soil strength layers that inhibited sordan root growth. The characteristics of acid, Al tolerance, and penetration of high soil strength make EG valuable in establishing grassed buffers, vegetative conservation barriers, and pastures in extremely acid or dense soils.

ZINC EXTRACTABILITY AS A FUNCTION OF pH IN ORGANIC WASTE-AMENDED SOILS

The distribution of various forms of heavy metals after addition to soils needs study to improve predictions of metal solubility, especially when the metal is added to soils with large quantities of organic carbon that oxidize over time. The extractability of added zinc (Zn) was determined in a laboratory study using sequential extractions as a function of pH and organic matter (OM as biosolids) additions to A and B horizon samples of three soils from the Coastal Plain of Maryland. The study used Galestown loamy sand (Psammentic Hapludults), Bertie silt loam (Typic Hapludults), and Othello silt loam (Typic Endoaquults), chosen to represent a typical toposequence in this physiographic province. Watersoluble Zn in the six horizons, with and without biosolids added, decreased with increasing pH from 4.0 to 7.0 and increasing cation exchange capacity (CEC) from 2.2 to 106 mmol c /kg soil. Although this decrease with increasing pH was expected, exchangeable levels of Zn were positively correlated with the CEC only up to pH 5.8 but were negatively correlated at pH > 5.8 in all the soils, suggesting that CEC was not a major contributor to Zn exchangeability at pH > 5.8. The biosolids amendment increased the solubility of Zn in all soils at pH 5.8 in all of the soils. The results indicate that pH was a controlling variable for the redistribution of water-soluble, exchangeable, and nonexchangeable Zn affected by biosolids addition. The higher level of nonexchangeable Zn in the Bertie soil compared with other soils, about 0.80 mmol/kg soil for the biosolids treatments and 0.47 mmol/kg soil for the soils without biosolids at pH 7.0, was attributed to the presence of higher native organic C levels and Fe(III) and Mn(III, IV)(hydr) oxide contents that enhance surface-induced hydrolysis and chemisorption of Zn. The effect of biosolids addition on nonexchangeable Zn retention was more pronounced in B horizons of all the soils, especially at pH > 5.8. The results have implications for predicting the mobility and bioavailability of Zn in soils in which pH and organic C levels are modified purposefully for the disposal of heavy metal and C-rich wastes.

No-Till Corn Yields and Water Balance in the Mid-Atlantic Coastal Plain

Water is the main limiting factor to rainfed corn (Zea mays L.) yield in the mid-Atlantic coastal plain. This study was conducted to determine the water balance, yields, and efficiency of water use (EWU) of no-till rainfed corn grown on three soils of varying water-holding capacity, a Wickham sandy loam (fine-loamy, mixed, thermic, Typic Hapludults) and two Bojac soils, a sandy loam and a loamy sand (coarse-loamy, mixed, thermic, Typic Hapludults). Soil water balance was determined from climate data and weekly measurements of soil moisture from time domain reflectometry (TDR) probes. Water balance components of water stress, crop coefficients, and evapotranspiration were determined for vegetative, tasseling, and grain-fill growth stages in 1998 and 1999. Yields were determined by overlaying georeferenced yield maps, order-1 soil survey maps, and locations of TDR probes. The EWU concept was defined as yield divided by [precipitation + (initial soil water content − final water content)], clarifying it from water use efficiency measurements that are calculated similarly but do not include drainage. Yields in 1998 (4833–12200 kg ha−1) were higher than 1999 yields (2245–8240 kg ha−1) due to higher growing season precipitation in 1998 (400 mm) than 1999 (220 mm). Drainage was determined in 1998, ranging from 65 to 105 mm. Minimizing drainage losses has potential for increasing the EWU and yields. This study establishes baseline water balance data for the mid-Atlantic coastal plain that can be used to parameterize computer models for investigating the effect of management practices on EWU and yields.

Contaminant mobility in soils amended with fly ash and flue-gas gypsum: Intact soil cores and repacked columns

The impact of the land application of coal combustion by-products, fly ash (FA) and flue-gas desulfurization gypsum(FDG), to coarse-textured soils of the southeastern U.S.A. wasinvestigated using batch and dynamic column techniques. Two FAsamples, one an alkaline FA (Alk-FA) and the other an acidic FA(Acid-FA), were evaluated alone and in combination with FDG assoil amendments to an Appling loamy sand (Typic Hapludults). Theeffects of these waste products on clay dispersion, soilhydraulic conductivity (Ksat) and the migration ofcontaminants such as Arsenic (As) and Boron (B) were studiedusing intact soil cores and repacked soil columns. FA or combinationsof FA + FDG were applied to the surface of intact soil cores (10 Mg ha-1) and repacked soil columns or incorporated withinrepacked soil columns. The columns were saturated and thenleached for a prescribed number of pore volumes to simulateleaching conditions in the field. Effluent pH, electricalconductivity (EC), and turbidity were monitored and leachatefractions were collected for B, As, Ca, Mg, K and Na analysis.Both FA materials were ineffective at decreasing the inherentdispersibility of clay from the Ap horizon in batch tests.In fact, high application rates of the Alk-FA induced some claydispersion in the well-flocculated Bt soil materials, andcolumn results suggest that incorporating the Alk-FA within thesurface soil may actually reduce Ksat. In contrast,treatments with FDG were highly effective at inducing rapid clayflocculation in batch tests and eliminating effluent turbidityfor intact and repacked soil columns. Boron was readily mobilefrom both intact and repacked soil columns, a majority of whichleached from the columns within the first three pore volumes.Boron leaching was greater for combined treatments (FA + FDG),possibly indicative of enhanced solubilization in the presenceof FDG or sulfate (SO4 2-) competition for sorptionsites. Arsenic levels present in the leachates from FA and FDGcolumns were generally lower than control columns and roughlycorrelated with effluent turbidity. Combined treatments (FA +FDG) enhanced Mg and K leaching due to the added competition ofCa for cation exchange sites. Following leaching, the intactsoil cores were sectioned at 5 cm intervals and the pH and EC ofthe soil, as well as the vertical distribution of As and B, weredetermined. Levels of residual As were only slightly higher in the upper section of the FA-amended columns, showing little downward movement, but no clear trend in residual B was observed due to its greater mobility.

Limestone, Gypsum, and Magnesium Oxide Influence Restoration of an Abandoned Appalachian Pasture

When restoring abandoned pastures on acidic hill-land soils to productivity, it is important to bring soil Ca and Mg to adequate levels. Gypsum is a readily available Ca amendment that is sufficiently soluble to move rapidly into the soil when surface-applied. Gypsum has been shown to reduce detrimental effects of subsurface acidity in soils of the southeastern USA. A 4-yr experiment was initiated to measure effects of surface gypsum application on forage production and to evaluate Mg-containing amendments to avoid gypsum-induced Mg deficiency. The study site was a southern West Virginia Gilpin silt loam (fine-loamy, mixed, mesic, Typic Hapludult) where abandoned hill-land pasture was being restored to productivity. Treatments included 0, 1000, 8000, 16 000, and 32 000 kg/ha flue gas desulfurization coal combustion by-product gypsum (gypsum) together with dolomitic limestone and five additional treatments to evaluate sources of supplemental Mg. Application of 16000 kg/ha gypsum together with limestone increased forage yields of mixed orchardgrass (Dactylis glomerata L.) and tall fescue (Festuca arundinacea Schreb) pasture during establishment by 42% and production by 11% compared with limestone alone. About 8% of the mean 790 kg/ha yield increase could be attributed to acidity-neutralizing effects of alkaline constituents in the gypsum by-product. Plants in higher gypsum treatments had higher concentrations of K and P, but gypsum application decreased soil and plant Mg concentrations. This indicated that gypsum should not be applied on typical acid soils without supplemental Mg.

Effect of poultry litter and composts on soil nitrogen and phosphorus availability and corn production

Environmental problems associated with raw manure application might bemitigated by chemically or biologically immobilizing and stabilizing solublephosphorus (P) forms. Composting poultry litter has been suggested as a means tostabilize soluble P biologically. The objectives of this study were to assessthe nutrient (N, P) value of different-age poultry litter (PL) compostsrelativeto raw poultry litter and commercial fertilizer and determine effects ofpoultrylitter and composts on corn (Zea mays) grain yield andnutrient uptake. The research was conducted for two years on Maryland'sEastern Shore. Six soil fertility treatments were applied annually to aMatapeake silt loam soil (Typic Hapludult): (1) a check without fertilizer, (2)NH4NO3 fertilizer control (168 kg Nha−1), (3) raw poultry litter (8.9 Mgha−1), (4) 15-month old poultry litter compost (68.7Mg ha−1), (5) 4-month old poultry litter compost(59 Mg ha−1) and (6) 1-month old poultry littercompost (64 Mg ha−1). We monitored changes inavailable soil NO3-N and P over the growing season and post harvest.We measured total aboveground biomass at tasseling and harvest and corn yield.We determined corn N and P uptake at tasseling.Patterns of available soil NO3-N were similar between raw PL-and NH4NO3 fertilizer-amended soils. LittleNO3-N was released from any of the PL composts in the first year ofstudy. The mature 15-month old compost mineralized significant NO3-Nonly after the second year of application. In contrast, available soil P washighest in plots amended with 15-month old compost, followed by raw PL-amendedplots. Immature composts immobilized soil P in the first year of study. Cornbiomass and yields were 30% higher in fertilizer and raw PL amendedplotscompared to yields in compost-amended treatments. Yields in compost-amendedplots were greater than those in the no-amendment control plots. Corn N and Puptake mirrored patterns of available soil NO3-N and P. Corn Puptakewas highest in plots amended with 15-month old compost and raw PL, even thoughother composts contained 1.5–2 times more total P than raw PL. There wasalinear relationship between amount of P added and available soil P, regardlessof source. The similar P availabilities from either raw or composted PL,coupledwith limited crop P uptake at high soil P concentrations, suggest that raw andcomposted PL should be applied to soils based on crop P requirements to avoidbuild-up of available soil P.

Eastern Gamagrass Root Penetration in Adverse Subsoil Conditions

Eastern gamagrass [Tripsacum dactyloides (L.) L] (EG) is reported to exhibit acid tolerance and root penetration through claypans. To study its root growth in these conditions, a greenhouse column study was conducted under simulated soil stress conditions, using EG and sordan [Sorghum × drummondii (Steud.) Millsp. & Chase] as a comparison species. Treatments consisted of incomplete factorial combinations of plant species (EG and sordan), soil water potential (−10 and –300 kPa), lime (pH 3.5 and 4.8), and soil bulk density (Db) (1.3 and 1.7 g cm−3). The treatments were arranged as a randomized complete block design (RCBD). For some of the response variables that were analyzed at different depths, depth was considered as a subplot factor. Treatments were applied to Al-toxic Tatum Bt horizon material (clayey, fine, mixed, semiactive, thermic Typic Hapludults) used in the middle 30-cm section of 15 by 60-cm polyvinyl Cl (PVC) columns. Soil strength was determined at harvest by cone penetrometer resistance. Results indicated that EG tolerated acid, Al-toxic conditions, while sordan roots were sensitive to the low pH conditions. Eastern gamagrass roots penetrated high soil strength layers that inhibited sordan root growth. The characteristics of acid, Al tolerance, and penetration of high soil strength make EG valuable in establishing grassed buffers, vegetative conservation barriers, and pastures in extremely acid or dense soils.

Fractal dimensions of mass estimated from intact and eroded soil aggregates

Scaling of mass within soil aggregates is characterized with a power-law model relating mass, M, and radius, r, of aggregates. When distribution of mass is fractal, the constants of the power-law model are the fractal dimension of mass, D m , with a value <3, and a linear constant k m . Tillage may alter mass scaling in soil by changing the internal arrangement of matter inside aggregates. Estimates of D m and k m have been made from measurements of mass contained in aggregates covering a range of sizes, but they could also be obtained by eroding aggregates of a single size class. Studies on eroded aggregates have shown that matter may be concentrically arranged in soil aggregates as a result of wetting and drying processes. The objective of this study was to estimate and compare D m and k m values from intact and eroded aggregates from wooded and cultivated sites of the same soil. Soil aggregates were sampled from the surface horizon of wooded and cultivated sites of a Typic Hapludults (Gladstone series), an Aquic Hapludults (Holmdel series), and an Ultic Hapludalfs (Ryder series) soil. A group of initially large air-dried aggregates was subjected to cycles of erosion that removed concentric layers of soil leaving increasingly smaller aggregates. Volumes of intact and eroded aggregates were measured by submerging kerosene-saturated aggregates in a 1:1 mix of water and glycerin and estimating the volume displaced by solving a balance of forces. An equivalent aggregate radius, r, was calculated as the cubic root of aggregate volume. Parameters D m and k m , and the variance of k m (lacunarity), were estimated separately from the air-dried mass and r of intact and eroded aggregates with r>1 cm and r<1 cm . Scaling of mass was influenced by the soil type and soil management. In general, fractal scaling of mass was consistently found only in intact and eroded aggregates ( r>1) of the Gladstone and Holmdel soils. For the wooded Gladstone and Holmdel soils, mass scaling of intact and eroded aggregates was statistically characterized by the same values of D m and k m , suggesting a concentric arrangement of mass, but only within aggregates that are not subjected to tillage. The k m values of intact and eroded aggregates were correlated ( R=0.97) to aggregate bulk density of intact aggregates. Typically, small aggregates (r<1 cm) , aggregates from wooded sites, and intact aggregates had larger values of lacunarity than their corresponding counterparts. This study indicates that fractal scaling of mass cannot be assumed for all soils, but it can be maintained in cultivated soils despite changes in mass scaling introduced by tillage.

Leachate chemistry of field-weathered spent mushroom substrate.

Passive leaching by rainfall and snowmelt is a popular method to treat piles of spent mushroom substrate (SMS) before its reuse. During this field weathering process, leachate percolates into the underlying soils. A field study was conducted to examine the chemistry of SMS leachate and effects of infiltration. Two SMS piles were deposited (90 and 150 cm in height) over a Typic Hapludult and weathered for 24 mo. Leachate was collected biweekly using passive capillary samplers. The SMS leachate contained high concentrations of dissolved organic carbon (DOC; 0.8-11.0 g L(-1)), dissolved organic nitrogen (DON; 0.1-2 g L(-1)), and inorganic salts. The pH, electrical conductivity, and acid neutralizing capacity were 6.6 to 9.0, 21 to 66 ds m(-1), and 10 to 75 mmolc L(-1), respectively. Inorganic chemistry of the leachate was dominated by K+, Cl-, and SO24-. Leachate DOC was predominantly low molecular weight (<1000 Da) organic acids. During 2 yr of weathering, the 90-cm SMS pile released (per cubic meter of SMS) 3.0 kg of DOC, 1.6 kg of dissolved N, and 26.6 kg of inorganic salts. The 150-cm pile released (per cubic meter of SMS) 2.8 kg of DOC, 0.7 kg of dissolved N, and 13.6 kg of inorganic salts. The 150 cm pile retained more water and exhibited lower net nitrification compared with the 90-cm pile. The top 90 cm of soil retained 20 to 89% of the leachate solutes. Weathering of SMS in piles of 90 cm depth or greater may adversely affect ground water quality.

Impact of Light‐Weight Rolling on Putting Green Performance

The introduction of light‐weight rollers has contributed to the reconsideration of the practice of rolling golf putting greens. Studies were conducted in 1993 and 1994 to determine the effects of rolling on soil bulk density, putting green speed, turf quality, root mass, and thatch mass. Experimental ‘Penncross’ creeping bentgrass (Agrostis stolonifera L.) putting greens built on a United States Golf Association (USGA) specification root zone and on a Cecil gravelly sandy loam (Typic Hapludult clayey, kaolinitic, thermic) (native soil) root zone were mowed daily and subjected to four rates of rolling (0, 1, 4, or 7 times per week) with a light‐weight roller for a 10‐wk period. Soil bulk density did not change for any rolling frequency on the USGA green. Rolling rates of four and seven times per week increased bulk density on the native soil green by 4 and 3% in the first year while no changes were detected in the second year. Turf quality was diminished for rolling rates of four and seven times per week. Ball roll increased as the rate of rolling increased. Rolling rate did not alter root mass. Thatch levels were not affected by rolling frequency on the USGA green. On the native soil green, four and seven rolling treatments per week resulted in thatch levels 12 and 11% higher than the control. Rolling once per week appears to offer increased green speed without any deleterious turf effects.

Erodibilidade entressulcos e atributos de solos com B Textural e B Latossólico do sul de Minas Gerais

O objetivo deste trabalho foi determinar a erodibilidade entressulcos (Ki) de três solos de textura argilosa: Podzólico Vermelho-Escuro (PE) e Vermelho Amarelo (PV) e um Latossolo Roxo (LR), visando obter subsídios para a aplicação no modelo WEPP- Water Erosion Prediction Project - na região de Lavras (MG), bem como estudar a relação daquele parâmetro com alguns atributos físicos, químicos e mineralógicos dos solos. Foi adotado um delineamento experimental do tipo blocos inteiramente casualizados com os três solos, quatro declives (15, 25, 35 e 45%), cinco intensidades de chuva simulada (60, 50, 70, 90 e 120 mm h-1), com umedecimento prévio das parcelas, e cinco repetições. Foram determinados os valores de Ki, usando as intensidades médias das chuvas, as declividades das parcelas e as taxas médias de erosão entressulcos nos diversos tempos de coleta do deflúvio de cada chuva aplicada. Os resultados mostraram que o PV foi o solo que apresentou as maiores erodibilidades entressulcos (Ki) seguido do PE e LR. As erodibilidades entressulcos determinadas foram : 4,67 x 10(5) kg s m-4, para o PE; 6,85 x 10(5) kg s m-4, para o PV, e 3,38 x 10(5) kg s m-4, para o LR. Os atributos do solo que melhor se correlacionaram com a erodibilidade entressulcos foram os teores de óxidos de ferro e caulinita, a argila dispersa em água, o volume total de poros, as densidades do solo e de partículas, os teores de matéria orgânica e de agregados &lt; 0,105 mm de diâmetro.

Soil–landscape relationships at the lower reaches of a watershed at Bear Creek near Oak Ridge, Tennessee

The watersheds at Bear Creek, Oak Ridge, TN, have similar soil–landscape relationships. The lower reaches of many of these watersheds consist of headwater riparian wetlands situated between sloping non-wetland upland zones. The objectives of this study are to examine the effects of (i) slope and geomorphic processes, (ii) human impacts, and (iii) particular characteristics of soils and saprolite that may effect drainage and water movement in the wetlands and adjacent landscapes in one of these watersheds. A transect was run from west to east in a hydrological monitored area at the lower reaches of a watershed on Bear Creek. This transect extended from a steep side slope position across a floodplain, a terrace, and a shoulder slope. On the upland positions of the Nolichucky Shale, mass wasting, overland flow and soil creep currently inhibit soil formation on the steep side slope position where a Typic Dystrudept is present, while soil stability on the shoulder slope has resulted in the formation of a well-developed Typic Hapludult. In these soils, argillic horizons occur above C horizons on less sloping gradients in comparison to steeper slopes, which have Bw horizons over Cr (saprolite) material. A riparian wetland area occupies the floodplain section, where a Typic Endoaquept is characterized by poorly drained conditions that led to the development of redoximorphic features (mottling), gleying, organic matter accumulation, and minimal development of subsurface horizons. A thin colluvial deposit overlies a thick well developed Aquic Hapludalf that formed in alluvial sediments on the terrace position. The colluvial deposit from the adjacent shoulder slope is thought to result from soil creep and anthropogenic erosion caused by past cultivation practices. Runoff from the adjacent sloping landscape and groundwater from the adjacent wetland area perhaps contribute to the somewhat poorly drained conditions of this profile. Perched watertables occur in upland positions due to dense saprolite and clay plugging in the shallow zones of the saprolite. However, no redoximorphic features are observed in the soil on the side slope due to high runoff. Remnants of the underlying shale saprolite, which occur as small discolored zones resembling mottles, are also present. The soils in the study have a CEC of <10 cmol kg −1, silt loam textures and Fe d values of 0.5–4.3%. These soils are also mainly acidic and low in total carbon.