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  • 1990-1994  (203)
  • Geography  (203)
  • RA 4845  (203)
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  • 1990-1994  (203)
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  • Geography  (203)
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  • RA 4845  (203)
  • 1
    Online Resource
    Online Resource
    Tillage Studies with a Corn‐Soybean Rotation: Hydrology and Sediment Loss
    Wiley ; 1993
    In:  Soil Science Society of America Journal Vol. 57, No. 4 ( 1993-07), p. 1051-1055
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 57, No. 4 ( 1993-07), p. 1051-1055
    Abstract: When soybean [ Glycine max (L.) Merr.] is produced on sloping fields using conventional tillage and mechanical cultivation for weed control, potential soil losses are high, limiting production to relatively flat lands. With the advent of conservation tillage practices and herbicides for weed control, soybean production with tolerable soil losses on sloping fields has become technically possible. To evaluate soil loss under these new conditions, runoff and erosion were measured on six small watersheds that were farmed for 6 yr in a corn ( Zea mays L.)‐soybean rotation with conservation tillage. Two of the watersheds were chiseled each year, two others paraplowed, and the other two received no‐tillage. A rye ( Secale cereale L.) cover crop was established each winter following soybean. With average yearly rainfall of 930 mm, yearly runoff was 63.5 mm and varied between 28 and 108 mm. Average yearly soil loss for the 6‐yr period was 526 kg/ha, 〈 10% of the allowable soil loss. Two storms caused most of the erosion, with a single storm accounting for 42% of the total measured soil loss. Earlier, these same watersheds averaged 5750 kg/ha of measured soil loss during the corn years of a corn‐wheat‐meadow‐meadow rotation with conventional tillage.
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    URL: Article
    DOI: 10.2136/sssaj1993.03615995005700040028x
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 1993
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
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  • 2
    Online Resource
    Online Resource
    Axisymmetric Transport of Water and Solute underneath a Disk Permeameter: Experiments and Numerical Model
    Wiley ; 1994
    In:  Soil Science Society of America Journal Vol. 58, No. 3 ( 1994-05), p. 696-703
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 58, No. 3 ( 1994-05), p. 696-703
    Abstract: No analytical solution exists for two‐dimensional, axisymmetric flow of both water and solute underneath a disk permeameter. We developed a finite‐difference numerical scheme for such flows. Laboratory experiments were also conducted using a box containing repacked sand. A ¼‐sector disk permeameter was located on the surface in one corner. The disk, first containing pure water, was placed on the soil for 200 s. It was then removed, refilled with a KBr solution, and replaced at 225 s. Finally after 12.5 min the disk was removed and soil samples extracted along three radial transects under the disk. In two other experiments, the disk, containing only pure water, was left on the soil surface and soil samples removed at the end i.e., 6 and 14 min. A tensiometer inserted through one face of the box and located just 20 mm under the disk recorded the changing soil water pressure head with time, h ( t ). Good predictions of both the water content and Br − profiles were achieved with the numerical model, and good renditions of h ( t ) and the transient flow rate from the disk, q ( t ). Our results reinforce the need for caution when determining the soil's sorptivity from observations of q vs. t ½ . Care is required in deciding when q has indeed become steady. Numerical models, such as this one might serve as parameter‐identification tools when using a tracer‐filled disk permeameter to infer the chemical transport properties of soil.
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    URL: Article
    DOI: 10.2136/sssaj1994.03615995005800030009x
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 1994
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
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  • 3
    Online Resource
    Online Resource
    Field‐Scale Variability of Soil Properties in Central Iowa Soils
    Wiley ; 1994
    In:  Soil Science Society of America Journal Vol. 58, No. 5 ( 1994-09), p. 1501-1511
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 58, No. 5 ( 1994-09), p. 1501-1511
    Abstract: Spatial distributions of soil properties at the field and watershed scale may affect yield potential, hydrologic responses, and transport of herbicides and NO − 3 to surface or groundwater. Our research describes field‐scale distributions and spatial trends for 28 different soil parameters at two sites within a watershed in central Iowa. Two of 27 parameters measured at one site and 10 of 14 parameters measured at the second site were normally distributed. Spatial variability was investigated using semivariograms and the ratio of nugget to total semivariance, expressed as a percentage, was used to classify spatial dependence. A ratio of 〈 25% indicated strong spatial dependence, between 25 and 75% indicated moderate spatial dependence, and 〉 75% indicated weak spatial dependence. Twelve parameters at Site one, including organic C, total N, pH, and macroaggregation, and four parameters at Site two, including organic C and total N, were strongly spatially dependent. Six parameters at Site one, including biomass C and N, bulk density, and denitrification, and 9 parameters at Site two, including biomass C and N and bulk density, were moderately spatially dependent. Three parameters at Site one, including NO − 3 N and ergosterol, and one parameter at Site two, mineral‐associated N, were weakly spatially dependent. Distributions of exchangeable Ca and Mg at Site one were not spatially dependent. Spatial distributions for some soil properties were similar for both field sites. We will be able to exploit these similarities to improve our ability to extrapolate information taken from one field to other fields within similar landscapes.
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    URL: Article
    DOI: 10.2136/sssaj1994.03615995005800050033x
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 1994
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
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  • 4
    Online Resource
    Online Resource
    Erosion Effects on Soil Water Storage, Plant Water Uptake, and Corn Growth
    Wiley ; 1992
    In:  Soil Science Society of America Journal Vol. 56, No. 6 ( 1992-11), p. 1911-1919
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 56, No. 6 ( 1992-11), p. 1911-1919
    Abstract: Many investigators have suggested that the greatest negative effect of erosion on soil productivity is the decrease in available water‐holding capacity, but few have attempted to evaluate this relation directly. In this 4‐yr study, we evaluated the effects of past erosion on soil water storage, plant water uptake, and corn ( Zea mays L.) growth on a linear slope of Dubuque silt loam soil (fine‐silty, mixed, mesic Typic Hapludalf) in southwestern Wisconsin. Levels of past erosion were based on depth to red clay (2Bt horizon): slight, 0.95 m; moderate, 0.74 m; and severe, 0.45 m. The total quantity of plant‐extractable water that could be stored in the upper 1 m of slightly eroded soil (181 mm) was 7% more than that for moderately eroded soil (169 mm) and 14% more than that for severely eroded soil (159 mm). For all erosion levels, water retained in the 0.5‐ to 1.0‐m soil depth was utilized by corn. Erosion level had no negative effect on early‐season plant growth. As plant‐extractable water decreased to 〈 55 to 60% of total, evapotranspiration (ET) and vegetative‐growth rates decreased as erosion level increased. The greatest differences in ET rates among erosion levels were observed during a 35‐d period in the drought year of 1988 when rates averaged 3.7 mm d −1 for slight erosion, 2.6 mm d −1 for moderate erosion, and 2.2 mm d −1 for severe erosion. For the 3 yr in which plant water stress was observed, maximum plant heights for the slight erosion level averaged 7% more than those for moderate erosion and 13% more than those for severe erosion. Although the soil's capacity to store and supply water decreased as erosion increased, the observed effects of erosion level on grain and stover yields, grain‐yield components, and harvest populations typically were not significant.
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    URL: Article
    DOI: 10.2136/sssaj1992.03615995005600060044x
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 1992
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
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  • 5
    Online Resource
    Online Resource
    Rainfall Detachment and Deposition: Experiments with Low Slopes and Significant Water Depths
    Wiley ; 1991
    In:  Soil Science Society of America Journal Vol. 55, No. 2 ( 1991), p. 325-
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 55, No. 2 ( 1991), p. 325-
    Type of Medium: Online Resource
    ISSN: 0361-5995
    URL: Article
    DOI: 10.2136/sssaj1991.03615995005500020004x
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 1991
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
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  • 6
    Online Resource
    Online Resource
    Short‐ and Long‐Term Phosphorus Dynamics in a Fertilized Ultisol under Sugarcane
    Wiley ; 1993
    In:  Soil Science Society of America Journal Vol. 57, No. 4 ( 1993-07), p. 1027-1034
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 57, No. 4 ( 1993-07), p. 1027-1034
    Abstract: In Brazilian sugarcane production systems, P fertilizer represents a substantial input cost, yet it is used with low efficiency. Furthermore, extractants currently used to estimate available P in highly weathered soils are not satisfactory. Understanding soil P transformations is a prerequisite to improving estimates of available P and fertilizer use efficiency. We used a sequential P fractionation procedure to examine short‐term dynamics of P from fertilizer, residue returns, and soil, and long‐term changes in forms and quantities of soil P as a result of fertilization. Mulch and burn systems of residue management were imposed as treatments in field‐grown sugarcane ( Saccharum officinarum L.) in northeast Brazil. Both treatments had similar inputs of P from residues (8.7 kg ha −1 ) but, despite the higher “available” P content of the ashes, more of the added P was mobilized and taken up by the plant in the mulch system, probably due to the presence of roots within the decomposing litter and more intense root exploration of the topsoil as a result of an improved moisture regime. This improved moisture and P supply was reflected in a 45% higher ratoon yield in the mulch treatment. Fertilizer P applied in a furrow 20 cm deep with the plant crop was concentrated in the more labile fractions, and had a residual effect on the first ratoon of about 30%. Over the long term (10 yr) there was accumulation (about 144 kg ha −1 ) of fertilizer P in the top 30 cm (in both labile and stable fractions). Nearly one‐half of the increase was in the first 7.5 cm of soil, a reflection of limited mixing of broadcast applications and uptake from the 7.5‐ to 15‐cm layer.
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    URL: Article
    DOI: 10.2136/sssaj1993.03615995005700040025x
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 1993
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
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  • 7
    Online Resource
    Online Resource
    In Situ Measurement of the Effective Transport Volume for Solute Moving Through Soil
    Wiley ; 1992
    In:  Soil Science Society of America Journal Vol. 56, No. 3 ( 1992-05), p. 733-736
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 56, No. 3 ( 1992-05), p. 733-736
    Abstract: A simple field method for measuring the soil's effectively mobile water fraction during near‐saturated flow is presented. Initial charging of the immobile fraction θ im is achieved by first wetting the soil with a disk permeameter until steady conditions prevail. The disk is then removed and rapidly replaced, but now filled with a tracer solution. Subsequently after a period of infiltration with tracer (0.1 M KBr), the soil underneath is sampled. The ratio of the measured to applied concentration, c */ c m , in the samples will be the fraction of the soil's water that is effectively mobile. We assume that the antecedent tracer concentration is zero, and that the mobile fraction, θ m , is at concentration c m . Disk permeameters, set at the slightly unsaturated potential head ψ o = −20 mm, wetted Manawatu fine sandy loam to a water content of θ o = 0.414 m 3 m −3 . From analysis of the tracer concentrations measured under the disk, we deduced θ m to be just 0.203. This semimobility was in accord with the observed depthwise penetration of tracer, as well as other measures of mobility previously found by others from longer term leaching studies carried out nearby.
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    URL: Article
    DOI: 10.2136/sssaj1992.03615995005600030010x
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 1992
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
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  • 8
    Online Resource
    Online Resource
    Extractability of Phosphorus in Manure Pellets Enriched with Fertilizer Phosphorus
    Wiley ; 1990
    In:  Soil Science Society of America Journal Vol. 54, No. 2 ( 1990-03), p. 443-448
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 54, No. 2 ( 1990-03), p. 443-448
    Type of Medium: Online Resource
    ISSN: 0361-5995
    URL: Article
    DOI: 10.2136/sssaj1990.03615995005400020025x
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 1990
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
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  • 9
    Online Resource
    Online Resource
    Cover Crop Management of Polysaccharide‐Mediated Aggregation in an Orchard Soil
    Wiley ; 1991
    In:  Soil Science Society of America Journal Vol. 55, No. 3 ( 1991-05), p. 734-739
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 55, No. 3 ( 1991-05), p. 734-739
    Abstract: Soil carbohydrates, including microbial extracellular polysacchrides, stabilize soil aggregates and improve soil structure. This study examined whether short‐term managment of C inputs by cover crops and tillage affected polysaccharide‐mediated macroaggregation. Soil was sampled from a Californa prune ( Prunus domestica L.) orchard where an experiment comparing four management techniques, permanent grass cover crop, mowed cover crop, no‐till herbicide, and conventional tillage, had been in place for two seasons. Cover crops significantly increased saturated hydraulic conductivity, acid‐ex‐tractable heavy‐ fraction carbohydrates (those in soil denser than 1.7 g/mL), and macroaggregate slaking resistance over clean‐cultivated or herbicide treatments. Heavy‐fraction carbohydrates are probably mainly composed of microbial extracellualr polysaccharides produced in response to cover‐crop C inputs. Heavy‐fraction carbohydrates were significantly correlated with aggregate stability and satureated hydraulic conductivity, while total organic C and lightfraction carbohydrates were not. There were no differences between soil under herbicide and clean‐cultivation treatments, showing that tillage alone did not measurably affect carbohydrate or soil structure. Heavy‐fraction carbohydrates were shown to be important in the initial improvement of soil structure by cover crops.
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    URL: Article
    DOI: 10.2136/sssaj1991.03615995005500030016x
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 1991
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
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  • 10
    Online Resource
    Online Resource
    Comments on “Fractal Dimensions of Soil Aggregate‐Size Distributions Calculated by Number and Mass”
    Wiley ; 1993
    In:  Soil Science Society of America Journal Vol. 57, No. 5 ( 1993-09), p. 1393-1393
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 57, No. 5 ( 1993-09), p. 1393-1393
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    URL: Article
    DOI: 10.2136/sssaj1993.03615995005700050038x
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 1993
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
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