bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil Erosion Effects on Properties and Productivity of Two Kentucky Soils
Authors: Frye W. W. , Ebelhar S. A. , Murdock L. W. , Blevins R. L.
Published: July 2010

Few attempts have been made to identify the yield‐limiting effects of soil erosion and to quantify losses in soil productivity. The objective of our study was to determine the effects of moderate erosion on certain physical and chemical soil properties and on the productivity of two soils. Soils were the Maury soil at Lexington, Ky., and the Crider soil at Princeton, Ky. Both have strongly developed profiles and are in the family of Typic Paleudalfs, fine‐silty, mixed, mesic. The soils were known to vary in degree of past erosion at the sites. For moderately eroded and uneroded areas of the soils, we determined several physical and chemical properties and measured corn grain yields on both soils and cover crop yields on the Maury soil. Corn grain yields on eroded soils compared to uneroded soils were 12% lower for the Maury soil and 21% lower for the Crider soil. Lower yields of winter cover crops attributed to erosion on the Maury soil were 17, 30, 36, and 27%, respectively, for rye, crimson clover, big flower vetch, and hairy vetch. Available water‐holding capacity (0.33 minus 15 bar water) averaged 4 to 5% lower (volume basis) in the surface layer of the eroded soils. In general, the Ap horizon of eroded compared to uneroded soils had higher clay content, higher bulk density, lower organic matter content, and lower fertility status. Erosion substantially decreases the productivity of strongly developed soils, such as the Maury and Crider soils, and the effect is long lasting and difficult to ameliorate. Probably the most important yield‐limitng effect of soil erosion is the decrease in available water‐holding capacity caused by the increased clay content of the Ap horizon.
Managing Early Season Soil Temperatures in the Northern Corn Belt Using Configured Soil Surfaces and Mulches
Authors: Radke J. K.
Published: July 2010

Soil temperatures in the northern Corn Belt are often too low at planting time to allow optimum germination, emergence, and early seedling growth. Crop residues, which are beneficial for erosion protection or are the result of minimum tillage, generally retard the rate of drying and warming of the seedbed. We found that ridged soils dried faster starting at the peak of the ridges and continuing down their southerly exposed slopes. Maximum seedbed temperatures occurred either under the ridge peak or under the southerly exposed slope. The time of the diurnal maximum temperatures depended on the slope aspect. For example, a southeast‐facing slope reached maximum temperature over 2 h earlier than a southwest‐facing slope, although the southwest slope reached a higher maximum temperature. Mulch decreased daytime soil temperatures, but a combination of mulch and ridging offset this temperature decrease so that there was no difference between a seedbed temperature under a mulch‐covered ridge and a conventionally tilled soil without mulch. Mulch with ridging provides a limited means of managing soil water and soil temperature in the seedbed.
The Mechanism of Raindrop Splash on Soil Surfaces
Authors: Al‐Durrah M. M. , Bradford J. M.
Published: July 2010

From the results of high‐speed photography of 4.6‐mm‐diam drops impacting various soil materials and from soil mechanics principles, a new concept in describing the mechanism of soil detachment from raindrops impacting on saturated soil surfaces is proposed. The impulsive loading caused by the impacting drop does not permit time for drainage; thus there is no change in total soil volume or bulk density. The soil surface is deformed under the impulsive load application of the drop; however, the vertical strain under the impact area is compensated by a bulge around the perimeter of the depression. The vertical force of the drop is transformed to lateral shear caused by radial flow of the impacting drop. Splash angle is determined by the depth of the cavity and the size of the bulge surrounding it.

Splash angle was highly correlated with soil shear strength as measured by the fall‐cone method. Low soil strength resulted in (i) a larger cavity and surrounding bulge, (ii) a greater detachment of soil particles due to the shear stress of the radial flow, and (iii) a greater splash angle with the horizon.
Rapid Method for Determining the Adsorption of Nickel‐63 to Kaolinite
Authors: Angle J. S.
Published: July 2010

A supernatant isolation system was investigated as a means to assay 63Ni adsorption to kaolinite. The Titertek Supernatant Collection System utilizes microtiter wells as the reaction chamber and cellulose‐acetate cartridges to separate kaolinite from supernatant. The 63Ni absorbed into the cartridge was assayed on a scintillation counter.

The supernatant of 96 wells could be separated from the kaolinite in under 5 min. The coefficient of variation for all measurements averaged 6.83%. The primary limitation of this system is the lengthy equilibration time.
A New Method for Determination of 15N‐Labeled Nitrous Oxide
Authors: Mulvaney R. L. , Kurtz L. T.
Published: July 2010

A procedure is described that permits determination of nitrous oxide (N2O) evolved from soils treated with 15N‐labeled fertilizer. This procedure involves dilution of 15N‐labeled N2O with a known amount of unenriched dinitrogen (N2), reduction of the N2O to N2 in a heated tube containing reduced copper, and determination of the ratios, 29N2/28N2 and 30N2/(28N2 + 29N2), with a dual‐inlet ratio mass spectrometer. The procedure described is accurate and precise; it permits measurement of 15N‐labeled N2O without interference by CO2; it allows calculation of the average 15N enrichment of the nitrogen pool from which this N2O is derived; and it permits N2O analysis of an atmospheric sample previously analyzed for 15N‐labeled N2.
Soil Profile and Site Characteristics Related to Winter Wheat Response to Potassium Fertilizers
Authors: Schaff Bernard E. , Skogley Earl O.
Published: July 2010

Eighteen sites throughout Montana were selected to study soil and climatic factors that influence the response of winter wheat (Triticum aestivum L.) to K fertilizer. Rates of 0, 22, 45, 90, and 135 kg K/ha were applied with 45 and 56 kg/ha of N and P, respectively. The sites were characterized according to Soil Taxonomy classification parameters. Fourteen chemical and physical properties were determined for each genetic horizon and seven site characteristics were identified. A stepwise multiple linear regression analysis was used to determine the relationship of the chemical, physical, and site characteristics to percent yield response of winter wheat to applied K. The genetic horizon variables were analyzed by major horizon as well as by sequence of horizons. Statistically significant variables (p < 0.1) from the major horizon analyses were grouped with significant site characteristics in a combined overall analysis. Variables with the highest correlation to percent yield response in the combined analysis, in decreasing order, were: (i) mean annual soil temperature at 50 cm as derived from SCS estimates; (ii) moist consistence of the Ap; (iii) moist and (iv) dry consistence of the B horizon; and (v) the clay content of the ca horizon. For these five variables an R2 of 0.88 was obtained.
A Laboratory Method for Predicting the Size Distribution of Sediment Eroded from Surface Soils
Authors: Rhoton F. E. , Meyer L. D. , Whisler F. D.
Published: July 2010

A laboratory method was developed to reproduce size distributions of sediment eroded from field plots during simulated rainstorms. Using samples of surface soil from the field plots, sediment size data were generated in the laboratory by agitating soil suspensions on an orbital shaker after wetting the sample under tension. Once agitated, the samples were separated into 10 size groups ranging from >1,000 to <4 µm by wet sieve and sedimentation procedures. Size distribution curves were prepared from these data and compared with appropriate field sediment curves. Agitation times were adjusted until most points on the laboratory curves were within ±1 SD of corresponding points on the field curves. Soils high in sand and silt produced laboratory and field curves which were quite similar, but curves from soils high in clay and organic matter were less similar. Results from the 17 soils studied indicate that laboratory generated sediment size data can be used to predict size distributions of sediment eroded by simulated rainfall from interrill areas.
Dry Soil‐Aggregate Stability: Energy‐Based Index
Authors: Skidmore E. L. , Powers D. H.
Published: July 2010

Most methods used to estimate aggregate stability apply an unmeasured force, or a measured force without knowledge of transfer, to a single or a group of aggregates. A technique is needed to estimate aggregate stability based on quantitative transfer of energy. This paper presents an energy‐based procedure for evaluating dry‐aggregate stability. Soil aggregates were crushed by diametrically loading them between parallel plates. The energy of crushing was determined by integrating the area under the force against distance curve. The aggregate‐surface area after comminution was calculated from aggregate‐size distribution and aggregate density; the aggregates were assumed to be spherical. The results are expressed as energy per unit of surface area, joules per meter squared (J/m2). Example values obtained from field‐sampled aggregates for several soil series ranged from 3.7 ± 0.7 for Hotlake silt loam (coarse‐silty, mixed, mesic Aquic Haploxerolls) to 43.9 ± 7.5 for Bearden silt loam (fine‐silty, frigid Aeric Calciaquolls). The wide range of aggregate stabilities among different soils made it possible to distinguish among them even though variability among aggregates of the same soil was relatively large. The results were relatively insensitive to initial aggregate size but sensitive to crushing end point.
Comparison of Fall and Spring Applications of 15N‐Labeled Urea to Douglas‐Fir: II. Fertilizer Nitrogen Recovery in Trees and Soil after 2 years
Authors: Heilman P. E. , Dao T. H. , Cheng H. H. , Webster S. R. , Christensen L.
Published: July 2010

Thirteen separate tree components were sampled for estimation of dry weight and for analysis for total N and 15N on relatively high site quality plots that had been treated with 224 kg N/ha as 15N‐labeled urea. Although the increase in volume growth from fertilization was significant, we were unable to demonstrate a significant increase in weight of any tree component including foliage and boles. Specific gravity of bole wood was significantly reduced by urea fertilization. Fertilization significantly increased concentration of N in the 1977 and older foliage, in bole wood, and in bole bark, but not in other biomass components including roots. The only component in which total weight of N was significantly increased by fertilizer was bole wood.

Fertilizer N in individual components as a percent of the total N in those components averaged 22.3% in 1979 foliage, 27.5% in 1978 foliage, 17.1% in 1977 and older foliage, 13 to 17% in twigs and branches, 19% in bole wood produced since fertilization, 19% in bole bark, and 16% in roots. Foliage contained an average of 55% of the total fertilizer taken up by the trees.

Fertilizer N in the total tree varied from 25 to 36% of the application. Volume growth response directly corresponded to the quantity of fertilizer N recovered in trees. Differences both in N fertilizer in trees and in volume growth response appeared related to pattern of rainfall soon after treatment. Fertilizer accounted for in soils and trees at the end of two growing seasons averaged 68% of the application. Lowest recovery (52%) corresponded to the treatment which had lowest rainfall after application. Real and apparent N loss averaged 32 ± 6% of the application. Causes of apparent losses likely include litter falling outside of the plots, transport of N beyond the plots by roots passing below the plot barriers, and leaching to deeper soil depths than sampled but still in the rooting zone. Relative magnitudes of real and apparent losses of N were not determined.
Seasonal Variation in Nutrients of Floodplain and Upland Forest Soils of Central Illinois
Authors: Peterson David L. , Rolfe Gary L.
Published: July 2010

Variation in nutrients was studied over a two‐year period in adjacent floodplain and upland forest soils in central Illinois. Nutrient pools of all elements except Na were greater in floodplain soils than in upland soils and were in the following order at both study sites: exchangeable Ca > exchangeable Mg > exchangeable K > available P. Seasonal variation in nutrient content of soils was the result of several environmental factors. Available P in floodplain soils was highly dependent on pH, which was in turn influenced by flooding, but there was no evidence of seasonal variation in available P for upland soils. Soil pH was positively correlated with the concentration of exchangeable bases in both soils, especially Ca and Mg in upland soils. Exchangeable Na was highly variable at both floodplain and upland sites and may have been influenced by leaching and variation in tree root exudation. The seasonal variation in nutrient pools of forest soils in this study has implications for tree growth, site evaluation, and nutrient cycling in forest stands.
Measurement of a Cation Exchange Isotherm from Elution Curves Obtained in a Soil Column: Preliminary Results
Authors: Schweich D. , Sardin M. , Gaudet J‐P.
Published: July 2010

It is shown how successive column experiments allow the measurement of exchange capacity and a composition‐dependent selectivity factor for the calcium‐potassium exchange process on a natural soil. The method is based on a simple model which describes (i) the coupling between the steady flow and the exchange process, and (ii) the solubility of calcite which is taken into account by assuming that the resulting excess in calcium is already in the feed. Comparison with classical batch measurements shows that the column experiments give more reliable results. Nevertheless, the accuracy of the method is limited by the efficiency of the packing of the column.
Line‐Source Sprinkler Systems for Experimentation with Sprinkler‐Applied Nitrogen Fertilizers
Authors: Lauer D. A.
Published: July 2010

A triple line‐source system was developed and evaluated as an alternative field plot design that allows superimposition of a continuous gradient of sprinkler‐applied N within uniform sprinkler irrigation. Two outer laterals are used to apply water only while a third lateral centered between the outer laterals is used to apply water plus injected N fertilizer. This layout provides duplication of the N gradient on each side of the center lateral. Equality of slopes and intercepts of linear regressions individually fit on both sides of the center lateral indicates good duplication and symmetry of the N gradient about the center lateral. The main disadvantage of the technique is the potential statistical bias stemming from the nonrandom treatment arrangement. Having good symmetry of response variables across the N source line indicates lack of statistical bias associated with nonrandom treatments because of the low probability that unknown gradients coincident with the N gradient would exist at the same magnitude at 180 degrees to each other. The technique is probably best suited for single independent variable investigations which exhibit large treatment differences relative to potential bias. In using this or any other continuous variable designs, the main inherent disadvantage of nonrandom treatment arrangement must be balanced against the main inherent advantages of smaller plot areas associated with the elimination of border areas and considerable savings of other research resources.
Soil Properties in a Mesquite‐Dominated Sonoran Desert Ecosystem
Authors: Virginia Ross A. , Jarrell W. M.
Published: July 2010

Soil was collected in 30‐cm depth increments to 90 cm from beneath Prosopis glandulosa Torr. var. glandulosa (L. Benson) M. C. Jtn. (mesquite) and from the nonvegetated area between mesquite trees in a phreatophytic stand in the Sonoran Desert of southern California. Total N, NO‐3‐N, NH+4‐N, organic C, NaHCO3‐extractable PO3‐4‐P, and saturation extract K+ were significantly higher beneath mesquite, while Na+ and Cl‐ were significantly higher between mesquite trees. Differences in pH, the osmotic potential of saturation extracts, saturation percent, and SO2‐4‐S were nonsignificant. Large amounts of N (1.68 g kg−1 of soil) have accumulated in the surface 30 cm beneath mesquite. This N most likely had been symbiotically fixed by mesquite. Over 20% of the N in this ecosystem occurred as NO‐3. This unusual NO‐3 accumulation was possible since leaching and denitrification were probably limited by aridity. The Na+ adsorption ratio of saturation extracts (SAR), 0–30 cm, was significantly lower at the center of tree canopies (7.9) than in soil between trees (17.3) and also was lower than the groundwater (12.7). Foliar analysis indicated mesquite was excluding Na+. Consequently, the decomposition of mesquite litter produced a soil with a lower SAR than the nonvegetated soil. Soil N was determined at six additional Sonoran Desert sites. Nitrogen accumulation beneath mesquite was related to soil texture and water regime. Total soil N was highest on low relief phreatophytic sites with high clay content (1.34 g of N kg−1 of soil, 0–15 cm) and lowest in aeolian sand dunes (0.18 g of N kg−1 of soil, 0–15 cm). Woody legumes such as mesquite, through the accumulation of symbiotically fixed N and the accretion of other nutrients in the surface beneath their canopies, may be important in maintaining the long‐term productivity of some desert ecosystems.
The Effect of Suspended Solids in Wastewater on Soil Hydraulic Conductivity: II. Vertical Distribution of Suspended Solids
Authors: Vinten A. J. A. , Mingelgrin U. , Yaron B.
Published: July 2010

A method for labelling of suspended solids in sewage effluent is used to trace the distribution of deposited solids in three soils following leaching with effluent. This distribution is related to the effect of sewage effluent application on the soil hydraulic conductivity. A sand, a sandy loam, and a loessial silt loam were studied. The reduction in relative hydraulic conductivity was greatest for the silt loam. This was due to accumulation of solids at the soil surface. In the sand little deposition of solids in the soil and little change in hydraulic conductivity occurred. Results indicate that with proper management sewage effluent can he used for irrigation without causing problems due to lack of soil permeability.
A General Soil Volume Change Equation: II. Effect of Load Pressure
Authors: Giráldez Juan V. , Sposito Garrison
Published: July 2010

The two‐parameter model of soil volume change developed by the authors is extended to account for the load pressure effects expected in the upper 2 m of a soil profile. The extended model equation is based on two principal assumptions: (i) that only the dry soil pore volume and the air‐entry water content are affected significantly by changes in load pressure, and (ii) that changes in the dry soil pore volume with load pressure are proportional. These assumptions require only one additional adjustable parameter in the extended model, the soil bulk modulus. The extended model describes available data on soil volume change under load pressure very well.
Influence of Velocity on Hydrodynamic Dispersion during Unsteady Soil Water Flow
Authors: Bond W. J. , Smiles D. E.
Published: July 2010

A recent solution of the equation for hydrodynamic dispersion during unsaturated, unsteady soil water flow is extended to include the velocity dependence of the dispersion coefficient. The effect of this velocity dependence on the solute concentration profiles is illustrated for the case of horizontal constant concentration absorption of water by an initially dry soil. The application of the theory to other soil water flow situations, including constant flux absorption, is also examined.
Fixation Kinetics in Potassium–Iron—Orthophosphate Systems
Authors: Kim Y. K. , Gurney E. L. , Hatfield J. D.
Published: July 2010

The rate of removal of phosphate and potassium from solution was studied by contacting an iron‐impregnated, cation exchange resin with solutions of monopotassium orthophosphate in concentrations of 0.05 to 0.25M and with atomic ratios Fe:P from 0.25 to 4.0. The removal of both P and K from solution followed first‐order reaction models for all experimental conditions, the K being removed faster than the P. The rate constants, k1 and k2, for P and K removal, respectively, increased with the ratio Fe:P and were affected to a lesser extent by the initial concentration of KH2PO4. The concentration of Fe with time agreed with a consecutive first‐order reaction mechanism involving liberation, k3, and precipitation, k4, of Fe. The rate constants were evaluated by nonlinear regression analysis, and the reaction model represents the data well. The rate constants, k3 and k4, increased with the ratio Fe:P, whereas increasing the initial concentration of KH2PO4 caused k3 to increase and k4 to decrease. The precipitate was prepared in 1M KH2PO4 solution and identified as potassium iron phosphate, K[Fe(OH)1.33]3·(H2PO4)6·2H2O, by chemical and x‐ray analysis.
Effects of Nitrogen and Phosphorus Application Method and Nitrogen Source on Winter Wheat Grain Yield and Leaf Tissue Phosphorus
Authors: Leikam D. F. , Murphy L. S. , Kissel D. E. , Whitney D. A. , Moser H. C.
Published: July 2010

The positive effect of placing N (especially NH+4‐N) with P on crop growth has been demonstrated many times in short‐term greenhouse studies. Under field conditions, however, the effect has not been well defined. The present objective was to evaluate N and P placement methods on the P nutrition and final grain yield of wheat (Triticum aestivum L.) grown in the field and greenhouse. Anhydrous ammonia (NH3), urea‐ammonium nitrate solution (UAN), and sodium nitrate (SN) were N sources while liquid ammonium polyphosphate (APP) was the P source. Methods of N‐P application included: knife N‐knife P (‘dual knife’), knife N‐hroadcast P, broadcast N‐knife P, and broadcast N‐broadcast P. Two nitrification inhibitors were included in some studies. In the greenhouse, APP was labelled with 33P orthophosphate and 32P pyrophosphate to examine P uptake of its ortho‐ and polyphosphate fractions with different N‐P‐K application methods each with either a NH+4‐N or NO‐3‐N source.

Dual knife N‐P applications gave higher leaf P concentrations and grain yields than other N‐P application methods in many of the field studies when ammoniacal N sources were used. Sodium nitrate dual knife applications were not as effective as dual knife applications of UAN or ammonia. The inclusion of the nitrification inhibitor nitrapyrin to dual knife treatments increased grain yield and/or leaf tissue P level in two 1978 studies, but had no effect in 1979. In the greenhouse the highest leaf P levels resulted from the banded NH3‐APP application. The banded SN‐APP application gave the second highest P uptake. This study also demonstrated that the N and APP need to be placed together, not separately in the soil. The amounts of the initial ortho‐ and polyphosphate portions of the APP absorbed by the plants seemed to be a function of fertilizer P demand and not related to fertilizer N in the same band. Including KCl in a band of APP did not affect leaf tissue P concentrations.
Densities of Wet Aggregated Sediment from Different Textured Soils
Authors: Rhoton F. E. , Meyer L. D. , Whisler F. D.
Published: July 2010

The density of wet aggregated sediment is a major factor controlling its fluvial transport and deposition. Since this property varies depending on the volume of aggregate pores filled with water, the use of dry aggregate densities in sediment transport studies may result in significant underestimations of wet sediment densities and consequently overestimations of transport distances. Therefore, this study was conducted to measure the densities of wet aggregates that exist during fluvial transport of sediment from agricultural soils. Samples from six soils, ranging in texture from silty clay to sandy loam, were wetted and agitated to simulate the stresses of raindrop impact. Two size ranges (1.00 to 0.50, and 0.50 to 0.25 mm) were collected from this sediment by wet sieving, then drained at a suction of 50 cm of water and weighed. The sediment volume was measured to the nearest 0.05 mL in a displacement vessel. Wet aggregate densities approximated 2.0 Mg/m3 and varied little among soils, or between the two size ranges. No variations in aggregate density could be directly attributed to differences in aggregate textures.
Distribution of Phosphorus Forms in Virgin and Cultivated Soils and Potential Erosion Losses
Authors: Sharpley A. N. , Smith S. J.
Published: July 2010

The relative amounts and distribution of P forms in virgin soil profiles are compared with those of similar soils that had been cultivated and fertilized for at least 15 years. Eight agriculturally important soil series, representative of different U.S. cropping areas, are included. Cultivation and fertilizer P application resulted in an increase in the total and inorganic P content for five soils and a decrease in organic P content for seven of the eight soils. Overall the change in total, inorganic, and organic P contents of cultivated surface horizons was +25, +118, and −43%, respectively. Fertilizer P application and mineralization of organic P during cultivation increased the available P (Bray‐I) content of all surface horizons. The content of all P forms in the subsoils was relatively unaffected by cultivation. Little change in total N/organic P ratio, exchangeable K, and cation exchange capacity was observed with cultivation and profile depth. The change in content of P forms with cultivation and fertilizer P application was closely correlated with P content of the virgin soils and amount of fertilizer P added during cultivation. The effect of sheet erosion of the surface 15 cm of virgin and cultivated soil on the content of P, N, and C forms, was estimated by comparing the nutrient contents of the 0‐ to 75‐ (uneroded) and 15‐ to 90‐cm (eroded) depths. Sheet erosion of the surface 15 cm of soil would reduce the inorganic P, organic P, available P, mineralizable N, and organic C contents of the virgin soil profile by an average of 15, 18, 25, 46, and 31%, respectively, while increasing P sorption index by 51%. The percent decrease in these P, N, and C forms (16, 2, 9, 35, and 22%) in the cultivated soil profile following sheet erosion was smaller than for the virgin soil. In general, simulated sheet erosion affected the P status of the soil profiles less than that of N.
Displacement of Nutrients into Windrows during Site Preparation of a Flatwood Forest
Authors: Morris Lawrence A. , Pritchett William L. , Swindel Benee F.
Published: July 2010

Nutrient displacement into windrows during site preparation, which followed the harvest of a natural stand of slash (Pinus elliottii Engelm.)—longleaf (Pinus palustris Mill.) pine, was examined on a 36‐ha flatwoods site in northcentral Florida. Almost 150 m of windrow were formed per hectare of site‐prepared area. The average width of the windrows was 4.2 m. The windrows averaged 2.5 m2 in cross‐sectional area and occupied approximately 6% of the harvested area. Total weight of the soil, fine wood, and coarse wood components were 154, 12, and 14 t/ha, respectively. Total N, P, and K contents were 373, 18, and 27 kg/ha of harvested area. These quantities of nutrients were equivalent to the quantities which would be removed in six bolewood harvests, and represented > 10% of the site's nutrient reserves.
Leaching of Soil Calcium, Magnesium, and Potassium in Irrigated Orchard Lysimeters
Authors: Neilsen G. H. , Stevenson D. S.
Published: July 2010

Leaching under intense irrigation and nitrogen fertilization has reduced soil basic cation concentrations and soil pH in irrigated apple orchards. The objective of this study was to measure the effects of N fertilizer and grass cover vs. clean cultivation on Ca, Mg, and K leaching, and to determine the changes in concentrations of these cations in soil and leaf and fruit tissue of ‘McIntosh’ apple trees (Malus domestica Borkh.). Twelve lysimeters, each containing an Osoyoos sandy loam soil and a single ‘McIntosh’ apple tree, have been monitored for Ca, Mg, and K concentration of soil, drainage water, and tree leaves and fruit from 1976 to 1980. Lysimeter treatments included factorial combinations of Kentucky bluegrass (Poa pratensis) and clean cultivation and two N fertilization rates [162 (N1) and 324 kg N ha−1 year−1 (N2) as NH4NO3]. Clean cultivation had the greatest effect on cation leaching with significantly higher Ca and Mg concentrations and higher Ca, Mg, and K losses frequently measured in drainage from these plots. By 1981, exchangeable Ca, Mg, and soil pH at the 0‐ to 0.10‐m soil depth in the cultivated plots had declined by 4.3 mmol kg−1, 2.2 mmol kg−1, and 0.3 units, respectively, relative to the grass plots. Drainage from N2 relative to N1 lysimeters had a significantly higher Mg concentration for 4 years but significantly higher Ca and Mg loss rates in only 1 year because of lack of differences in drainage volumes between N2 and N1 plots. Neither the cultivation or fertilizer treatments had altered Ca, Mg, or K concentration of McIntosh fruit or foliage in 4 years. For all lysimeters, Ca and Mg leached more rapidly than K. Annual losses over all treatments, 1976 through 1980, averaged 387 kg Ca ha−1, 118 kg Mg ha−1, and 44 kg K ha−1. Such leaching would eventually lead to enrichment of local soils with K relative to Mg and Ca. This is undesirable since McIntosh trees are susceptible to Mg deficiency and K:Ca antagonism. Therefore, periodic additions of Ca and Mg as through dolomitic liming should be considered for these orchards. Also, K fertilization accelerates existing trends to relative enrichment of these soils with K.
Evaluation of Fertilizer Phosphate Residues by Plant Uptake and Extractable Phosphorus
Authors: Olsen S. R. , Watanabe F. S. , Bowman R. A.
Published: July 2010

Residual phosphate from fertilizer P or manure seemed to accumulate mainly as octocalcium phosphate (OCP) in 23 alkaline and calcareous soils of eastern Colorado. Soil solution composition data were corrected for six ion pairs in calculating the calcium phosphate potential. These soils contained 37 to 162 mg kg−1 NaHCO3‐soluble P. Phosphorus removed by cropping varied between 58 and 275 mg kg−1 with five to eight crops before P deficiency reappeared. Phosphorus uptake was highly correlated with available P before cropping as measured by NaHCO3‐soluble P (four successive extracts), resin‐extractable P, and labile P by 32P isotopic dilution. Plants absorbed more P at equal initial concentrations of soluble P (in 0.01M CaCl2) from soils containing higher clay contents. All the OCP dissolved during cropping. This material seems to have a very high availability coefficient for plants. Accumulation of fertilizer P residues in this form would appear to be beneficial since this P is potentially all available to crops. Therefore, methods for estimating the amount of OCP in soils should be useful.
Comparison of Soil Phosphorus Extractants as Predictors of Mycorrhizal Dependency
Authors: Ojala J. C. , Jarrell W. M. , Menge J. A. , Johnson E. L. V.
Published: July 2010

To determine which of several soil P extraction techniques best predicted the response of citrus (Poncirus trifoliate X Citrus sinensis) seedlings to mycorrhizal fungi (Glomus fasciculatus), 25 nursery and field citrus soils from southern and central California were collected and analyzed for available P by five methods. Mycorrhizal dependency (MD), defined as the dry weight (mycorrhizal plants)/dry weight (nonmycorrhizal plants) × 100, was significantly correlated with the reciprocal of extractable soil P regardless of the extraction method. Those methods whose results depend most on soil solution P concentrations gave best results. Saturation extract P(PSE, R2 = 0.67***), anion exchange resin P(PAER, R2 = 0.57***), and 1:10 soil to water extract P(P1:10, R2 = 0.51***) were all acceptable for predicting mycorrhizal response. Bicarbonate‐extractable P (PB1C, R2 = 0.32**) and ammonium fluoride P (PAF, R2 = 0.19*) were less acceptable. Using regression models, based upon the reciprocal of the extractable‐P value, a MD > 200% was predicted where PSE < 0.65 mg L−1, PAER < 62 mg kg−1 soil, P1:10 < 0.66 mg L−1, PBIC < 34 mg kg−1 soil, and PAF < 54 mg kg−1 soil. Where analytical capabilities are adequate, PSE is the preferred method for predicting response, while PAER would suffice where higher analate P concentrations are required. Alternatively, inclusion of both PSE and PAER gave an excellent correlation with response (R2 = 0.82***). Inclusion of DTPA‐extractable Mn significantly improved regression equations in all cases except that of PSE, where DTPA‐extractable Zn significantly improved the relationship.
New Chemical Criteria for Defining the Spodic Horizon
Authors: Mokma D. L.
Published: July 2010

Many soils which morphologically appear to be Spodosols do not meet the chemical requirements for the spodic horizon. The purpose of this study was to develop new chemical criteria for defining the spodic horizon. New chemical criteria were developed using samples from 18 pedons and were further tested with samples from 28 soil monoliths. The proposed criteria for the spodic horizon are: (i) more Cp + Alp + Fep than the overlying E horizon or A horizon if the E horizon is absent; (ii) Cp + Alp + Fep ≥ 0.50%; (iii) Cp/ (Alp + Fep) atomic ratio is 5.8 to 25.0; and (iv) illuviation index ≥ 5.0 for subhorizons with 1, 2, and 3. All 32 pedons or monoliths with Spodosol morphology met the new chemical criteria. All 11 pedons or monoliths with nonSpodosol morphology failed to meet the criteria. One of the three monoliths with weak Spodosol morphology met the new criteria.
Soil Water Change as Related to Position of Wheat Straw Mulch on the Soil Surface
Authors: Smika D. E.
Published: July 2010

A field study was conducted in the Central Great Plains to determine the effects of the position of wheat straw mulch on soil water change of a silt loam soil (a montmorillonitic, mesic Aridic Paleustoll) during three 14‐month fallow periods. Treatments of 4600 kg/ha of wheat straw mulch flat on the soil surface, ¾ flat and ¼ standing, or ½ flat and ½ standing (normal position following standard combine harvesting) were compared with bare soil. Standing stubble was 0.46 m tall. Soil water content of one 1‐m3 hydraulic lysimeter within each treatment was measured daily and changes summed for each week, and at a distance of 2 m from each side of the lysimeter a neutron depth probe was used to determine soil water content weekly except when the soil was frozen. The relationship of soil water change for each weekly period with weekly values of total precipitation, total open‐pan (U.S. Weather Bureau Class A) evaporation, average daylight‐hour vapor pressure deficit, average maximum air temperature, average daily air temperature, average daylight‐hour air temperature, total solar radiation, and average daily wind movement, was determined by single and multiple‐correlation techniques. Soil water increases were related only to precipitation events with the highest correlation resulting from the ½ flat ½ standing wheat straw position treatment. Soil water losses were best correlated with wind movement with r2 values of 0.55, 0.41, 0.41, and 0.32 for bare soil, flat ¾ flat‐¼ standing, and ½ flat‐½ standing treatments, respectively. Soil water loss occurred from both bare soil and where the mulch was flat with winds of 0.08 MS−1. When ¼ or ½ of the mulch was standing, a wind of at least 0.55 MS−1 was needed before soil water loss occurred. Standing wheat straw does not function as a wick for loss of water from the soil.
The Effect of Exchangeable Sodium and Gypsum on Surface Runoff from Loess Soil
Authors: Keren R. , Shainberg I. , Frenkel H. , Kalo Y.
Published: July 2010

Surface runoff from a deep silt loam loess soil at two exchangeable sodium percentage (ESP) values (4.6 and 19.3), and the beneficial effect of industrial gypsum, were studied in field plots (of 150 m2 each) under natural rainfall conditions. The ESP of the soil was found to have a very pronounced effect on the surface runoff in spite of the fact that the final infiltration rate of the soil was affected only slightly by the ESP of the soil. The effect of ESP on the percent of surface runoff is probably through its effect on the rate of crust formation. The percent of surface runoff increased during the rainy season, for both ESP levels, because the runoff from already crusted soil was higher. However, the effect of consecutive storms depended on the degree of drying between storms. Application of industrial gypsum was found to be very effective in lowering surface runoff from the soil. Spreading the gypsum over the soil was more effective than mixing it in the upper 10 cm of soil by disk. Localization of the gypsum at the soil surface, where crust is formed, explains this effect. Gypsum application lowered the ESP of the upper 10‐cm layer for both gypsum treatments. Since the ESP of the soil in both gypsum treatments was about the same, it seems that the most important factor which controlled infiltration was the electrolyte concentration in the percolating solution.
Nitrogen Mineralization and Nitrification: Depth Variation in Four New England Forest Soils
Authors: Federer C. A.
Published: July 2010

Net nitrification and net nitrogen mineralization over 1 midsummer month were measured by in‐situ incubation at 14 depths in a single pit in each of four mature forest stands in New England. Nitrogen mineralization per unit of organic mass was greatest in the Oe horizon in two New Hampshire soils and in the upper A horizon in a Connecticut soil, and generally declined with increasing depth. In a Maine soil mineralization per unit of organic mass was independent of depth. Mineralization ranged from 2 to 14 kg N·ha−1 for 28 d in the four forest floors and from 3 to 12 kg N·ha−1 in the four mineral soils. Nitrification was not detected in any forest floors, but was 0.1 to 3.3 kg N·ha−1 for 28 d in the mineral soils. Both the large variation with depth and the contribution of mineral soil should not be overlooked when studying these processes.
The Effective Removal of Suspended Materials from Pyrophosphate Extracts of Soils from Tropical and Temperate Regions
Authors: Schuppli P. A. , Ross G. J. , McKeague J. A.
Published: July 2010

Sodium pyrophosphate (0.1M) extracts of some soil samples from Canada and East Malaysia were subjected to low‐speed centrifugation both without and with Superfloc, high‐speed centrifugation, and ultrafiltration of the centrifugates prior to determination of their Fe and Al contents. Relative to ultrafiltration, none of the centrifugation methods cleared the extracts completely and thus part of the extracted Fep and Alp measured in the supernatants was present in suspended solids. Suspended solids, with mineralogy similar to that of the clay of corresponding samples, were particularly abundant in the supernatants of the tropical soil samples after low‐speed centrifugation without Superfloc. Adding Superfloc to these extracts and centrifuging them at low speed sedimented practically all the aluminum silicates but concentrated the goethite in the material that remained suspended. High‐speed centrifugation gave similar results but with less concentration of goethite. Smaller amounts of suspended solids, also with mineralogy similar to that of the clay of corresponding samples, were present in the supernatants of samples from Canadian soils, except for that from a spodic horizon sample in which suspended minerals were absent. Ultrafiltration of the centrifugates through a 0.025‐µm millipore filter cleared the extracts effectively and is recommended for tropical soils and for soils giving doubtful results with centrifugation methods only. High‐speed centrifugation is probably adequate for most temperate‐region soils, as suspended Fe and Al in the extracts tested accounted for 0.1 dag/kg or less of sample weight.
The Persulfate Oxidation of Fungal Melanins
Authors: Martin F. , Gonzalez‐Vila F. J. , Martin J. P.
Published: July 2010

Four fungal melanins were degraded by potassium persulfate, a new, mild chemical oxidation method. The percentage of degradation varied from 15 to 50% calculated by weight loss. Analysis of the degradation products by gas chromatography showed numerous fatty acids, both straight and branched chain, in widely varying amounts. The n‐C16 and n‐C18 acids were present in greatest abundance. By two‐dimensional thin‐layer chromatography, several phenols and anthraquinones were noted.
Characteristics of Rhizobium trifolii Populations Associated with Subclover in Mississippi Soils
Authors: Hagedorn C. , Ardahl A. H. , Materon L. A.
Published: July 2010

Indigenous Rhizobium trifolii populations that would nodulate Trifolium subterraneum L. (cv. Mt. Barker) were isolated and characterized from pastures with and without subclover in five distinct soil regions in Mississippi. Considerable variation in effectiveness was found among isolates from the different areas and from individual sampling sites within areas, and the combined results indicated that subclover production and soil fertility levels were related and were being better maintained within two of the sampling areas. Pastures without clover yielded small R. trifolii populations that were poorly effective in N fixation on subclover. Significant correlations were found between the Rhizobium population size and soil N levels, soil texture, organic matter content, and exchangeable acidity. Isolate effectiveness was associated with the amount of base saturation, soil acidity, and N levels. These results are discussed in the context of subclover production as related to Rhizobium effectiveness, population size, and soil fertility characteristics.
Soil Fertility Dynamics after Clearing a Tropical Rainforest in Peru
Authors: Sanchez P. A. , Villachica J. H. , Bandy D. E.
Published: July 2010

This paper describes changes in soil properties during the first 8 y after clearing a fine loamy, siliceous, isohyperthermic Typic Paleudult at Yurimaguas, Peru. Three adjacent fields under a 17‐year old secondary forest were slashed, burned, and planted to three crops per year with or without fertilization for 8 years. Ash from the burn increased soil pH, available N, P, K, Ca, Mg, and decreased exchangeable Al. Six months after burning, however, the levels of available N and K were reduced, along with sporadic S, Cu, and B deficiencies. Topsoil organic C and total N decreased at an annual rate of 25% during the first year but approached an equilibrium afterwards. The rapid organic matter decomposition probably released organic matter‐bound Al which reversed the liming effect of the ash. Phosphorus and Mg became deficient during the second year, Ca within the first 30 months and Zn and Mn during the fourth year. Molybdenum deficiencies occurred sporadically, particularly when locally produced legume seed was used. Soil chemical properties have improved with continuous cultivation because of liming and fertilizer additions. After 8 years and 21 crops, topsoil pH increased to 5.6, exchangeable Ca increased by 10 times, effective CEC doubled, available P increased from 5 to 39 mg kg−1, and Al saturation decreased from 82 to 1%. The 15‐ to 50‐cm layer of the subsoil has undergone significant increases in exchangeable Ca and Mg and a decrease in Al saturation. This should promote deeper root development. The time at which nutrient deficiencies appeared and the amounts of fertilizer or lime needed to correct them varied substantially between the three fields, despite their close proximity, same preclearing vegetation, geomorphic position, and same soil classification at the family level.
Color Patterns and Water Table Levels in Some Indiana Soils
Authors: Franzmeier D. P. , Yahner J. E. , Steinhardt G. C. , Sinclair H. R.
Published: July 2010

In soils of sandy, coarse loamy, fine loamy, fine silty, and fine particle‐size families, we observed some general relationship between water table depths and soil color pattern. Horizons that have dominantly gray (chroma ≤ 2) color in the matrix or argillans are saturated much of the year. Horizons that have gray mottles, but are dominantly brown, are saturated a few months of the year if they are above the dominantly gray horizons, or are saturated most of the time if these horizons are below the dominantly gray horizon. Horizons that have dominant chroma of three in the matrix, mottles, or argillans are often saturated. Those that have dominant chroma of five or six and have no mottles with chroma of three or less are seldom or never saturated. This study shows that soils with three‐chroma matrix, mottles or argillans are much wetter than they had been thought to be and are wetter than reflected in Soil Taxonomy definitions.
Evaluation of Manual Cadmium Reduction Methods for Determination of Nitrate in Potassium Chloride Extracts of Soils
Authors: Dorich R. A. , Nelson D. W.
Published: July 2010

Although 2M KCl is widely used as an extractant for inorganic N in soils, most colorimetric NO‐3 methods are not applicable to such extracts. Keeney and Nelson (1982) have recently described a Cd reduction procedure for determination of NO‐3 in KCl extracts that was adapted from those used for water analysis. Other published manual Cd reduction methods may be applicable to analysis of KCl extracts of soils. The objectives of this work were to determine the conditions necessary for quantitative reduction of NO‐3 on the Cd column and to evaluate the applicability of Cd reduction procedures for the determination of NO‐3 in KCl extracts. Studies indicated that slower eluant flow rates and/or longer Cd columns than those specified in the Keeney and Nelson method resulted in nonquantitative recovery of added NO‐2 and NO‐3 due to destruction of NO‐2 by the Cd column. These findings indicated that the Keeney and Nelson method was the manual Cd reduction procedure best suited for analysis of KCl extracts. Nitrate added to 2M KCl extracts of soils was quantitatively recovered by the Keeney and Nelson method. The coefficient of variation for the method ranged from 2.1 to 3.4% when KCl extracts were analyzed over 3 d. Analysis of NO‐3 in 2M KCl extracts of soils established that the Cd reduction method gave values similar to those obtained by a steam distillation‐acidometric titration procedure and markedly higher that those with a brucine colorimetric technique. After KCl extracts had been prepared, approximately 36 samples could be analyzed per hour by the Keeney and Nelson procedure. The manual Cd reduction method using a 110 mL min−1 flow rate and a 20‐cm column is a rapid, precise, and accurate technique for determination of NO‐3 in KCl extracts of soils.