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Home » Journal of Soil and Water Conservation » Abstracts and Archives » Second Quarter 2001
Second Quarter 2001

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Second Quarter 2001 Table of Contents

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  • Wastewater Reclamation and Reuse for Aquaculture in Perú
    Hugo Nava

Research

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  • Book Review by Dr. J. Laflen

  • Letters to the Editor

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Mapping tillage practices with landstat thematic mapper based logistic regression models
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.2)

P. H. Gowda, B. J. Dalzell, D. J. Mulla, and F. Kollman 

ABSTRACT: Tillage information is crucial in environmental modeling as it has a direct impact on sediment delivery, phosphorus loss, and water holding capacity of agricultural soils. Remote sensing techniques can provide information about tillage practices over large areas. In this study, six Thematic Mapper (TM)-based logistic regression models proposed by van Deventer et al. (1997) were used to distinguish conventional and conservation tillage practices in the Lower Minnesota River watershed located in southern Minnesota. Accuracy assessments of tillage maps derived from Landsat TM data were made using field data collected by the Natural Resources Conservation Service (NRCS). Regression models were easy to use, cost and time effective, and produced reasonably accurate tillage maps. The "percentage correct" and kappa (k) values varied from 42–77% and 0.03–0.51, respectively, with best values for logistic regression models that use TM band 5 or the difference between TM bands 3 and 5 images. This approach is promising for the rapid collection of tillage information on individual fields over large areas. 

Keywords: Accuracy assessment, remote sensing, southern Minnesota, tillage

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Irrigation scheduling for a sandy soil using mobile frequency domain reflectometry with a checkbook method 
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.2)

C.A.M. Laboski, J.A. Lamb, R.H. Dowdy, J.M. Baker, J.Wright 

ABSTRACT: Time domain reflectometry (TDR) has changed the way researchers measure soil water content. A technology similar to TDR, called frequency domain reflectometry (FDR) can now be applied to practical field situations, such as irrigation scheduling. For this study, mobile FDR probes were inserted into the soil vertically and measured soil moisture in the upper 0.6 m of soil in two 0.3 m increments. The mobile FDR was used to measure soil moisture in many locations in three crops (corn, soybean, spring wheat) on selected days for two growing seasons. This information was used to update a checkbook method of irrigation scheduling and proved to be easy. Quick, mobile FDR measurements in several locations provided sound estimates of soil moisture throughout a field and allowed for enhanced water use efficiency and reduced leaching potential. 

Keywords: Checkbook method, corn, irrigation scheduling, mobile FDR, soybean, water quality, wheat

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Estimating the r-factor with limited rainfall data: a case study from peninsular Malaysia
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.2)

B. Yu, G. M. Hashim, and Z. Eusof 

ABSTRACT: Lack of long term, continuous pluviograph data makes it difficult to determine the R-factor for the Revised Universal Soil Loss Equation (RUSLE) in many parts of the world. Limited pluviograph data and long term daily rainfall data for two sites in Peninsular Malaysia were used to evaluate a daily rainfall erosivity model and estimate the R-factor and its monthly distribution. Mean annual rainfall for the two sites ranged from 1880–3070 mm, and the R-factor ranged from 13,600–21,600 MJ mm ha-1 hr-1 yr-1. A model using daily rainfall data to estimate monthly EI30 performed well with the coefficient of efficiency in excess of 0.87 and a mean discrepancy of less than 2% in the monthly distribution of rainfall erosivity. The rainfall erosivity model can be used to accurately estimate the R-factor and its seasonal distribution with long term daily rainfall data which are available in Malaysia, and elsewhere in the world. 

Keywords: Erosivity, RUSLE, soil erosion, tropics

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Measurement of soil translocation by tillage using a non invasive electromagnetic method
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.2)

L. Borselli and D. Torri 

ABSTRACT: The paper describes a non invasive technique for measuring tillage erosion using an electromagnetic probe that measures the magnetic susceptibility of the soil. Small iron nuts are buried in the soil, transported by tillage equipment, and coordinates of their new center of mass (CM) are then determined by surveying the perturbed magnetic susceptibility. The proposed method is quick—30 minutes per survey—for the CM-coordinates and one hour for a precise reconstruction of the shape of the cloud of tracers. On the other hand, the method does not describe the mixing of the soil because, differenting from the excavation-based methods, the tracers are dealt with statistically. 

Keywords: Electromagnetic survey, non invasive survey, soil translocation, tillage erosion, tracers

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Developing and testing a system for studying unsaturated solute transport on undisturbed soil blocks
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.2)

J.S. Strock and D.K. Cassel 

ABSTRACT: Primary limitations associated with conducting laboratory solute transport studies are related to size and shape of undisturbed soil cores, effective water delivery system, effluent collection, and experimentation under unsaturated conditions. Compounding the problem of conducting solute transport studies is the occurrence of preferential flow. The objective of this study was to develop and evaluate the equipment and protocols for conducting unsaturated preferential flow experiments on large, 38 cm by 38 cm by 65 cm deep, undisturbed soil blocks that reduce some of these limitations. System components include a rigid steel framework to assist in collecting undisturbed soil blocks; an 81 cell grid lysimeter plate for partitioning effluent outflow, and applying the desired soil water pressure at the base of the soil block; a bi-directional water drop applicator capable of delivering a range of application rates continuously over the entire soil surface; and a network of soil water monitoring devices for measuring volumetric soil water content and matrix potential. The soil block collected for this experiment was a Cecil sandy loam (Clayey, kaolinitic, thermic, Typic Kanhapludult) from the eastern United States Piedmont region. To evaluate the experimental system, potassium bromide (KBr) was applied to the soil surface (40 kg Br ha-1) and displaced through the soil block. Seventy percent of the cumulative effluent volume and 75% of the cumulative bromide (Br) mass were conducted through 50% of the basal area of the soil block. Cells that conducted high volumes of effluent (> 1000 mL) also transported considerable amounts of Br, r2 = 0.99. The experimental control offered by the equipment and procedures described in this study allow for detailed study of mechanisms controlling preferential flow of water and chemicals through soils under various boundary conditions. 

Keywords: Landscape position, macropore, preferential flow, transient flow, unsaturated flow

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Effects of emergency haying on vegetative characteristics within selected conservation reserve program fields in the northern Great Plains 
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.2)

A.W. Allen, B.S. Cade, and M.W. Vandever 

ABSTRACT: Successional changes in vegetation composition within seeded grasslands may affect attainment of long term conservation objectives. Comparisons between vegetation composition within Conservation Reserve Program (CRP) fields planted to cool season, introduced grasses hayed for emergency use, and non hayed fields of the same age and species composition were completed to determine potential effects of periodic haying. Emergency haying had little long term effect on vegetation height/density, percent cover of live grass, or forb cover when compared to characteristics within non hayed fields. The presence of legumes [primarily alfalfa (Medicago sativa L)] increased in response to haying, whereas, abundance of noxious weeds [chiefly Canada thistle (Cirsium arvense (L) Scop.)] diminished. Implications for long term management CRP grasslands to achieve wildlife habitat objectives are discussed. 

Keywords: Alfalfa, Conservation Reserve Program, emergency use, grasslands, haying, intermediate wheatgrass, management, wildlife habitat

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Tillage and fallow effects on selected soil quality characteristics of former conservation reserve program sites 
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.2)

J.E. Gilley, J.W. Doran, and B. Eghball 

ABSTRACT: Tillage and fallow have been suggested as management options for converting Conservation Reserve Program (CRP) areas to cropland. This study was conducted to measure selected soil quality characteristics of former CRP sites in Mississippi, Nebraska, and South Dakota that were tilled and then left fallow for 21 or 22 months. Soil samples from depth intervals of 0–7.6 cm and 0–30.5 cm were collected for laboratory assessment of the following soil quality indicators: bulk density, EC, pH, total C, organic C, total N, NO3–N, NH4–N, PO4–P, biomass C, biomass N, anaerobic NH4–N, lab respiration 0–10 days, and lab respiration 10–20 days. When compared to undisturbed CRP, increased NO3–N values on the tillage and fallow plots suggest that under the extreme conditions employed in this study, organic residues were being mineralized. As a result, significant reductions in organic C and total N were found at the 0–7.6 cm depth on each of the fallow plots. Thus, to reduce soil quality degradation, use of minimum-till or no-till management systems may be best suited for CRP areas which are converted to cropland. 

Keywords: Conservation benefits, grassland, land management, soil organic matter, soil properties

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Infiltration rates in fall-seeded winter wheat fields following preplant subsoil tillage 
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.2)

M.M. Mizuba and J.E. Hammel 

ABSTRACT: The Palouse region of eastern Washington and northern Idaho experiences high erosion rates on fall-planted wheat fields during the winter season. Increasing surface macroporosity through subsoil tillage can increase water infiltration, thereby decreasing erosion potential. Deep rip and paratill tillage treatments were established on an Ultic Argixeroll under a winter wheat (Triticum aestivum)/spring pea (Pisum sativum) rotation. Steady-state infiltration rates were measured using an unconfined infiltrometer following the seeding of winter wheat. Although both paratill and deep rip infiltration rates were higher during the fall, 0.41 cm min-1 and 0.30 cm min-1, respectively, compared to the non subsoiled control, 0.20 cm min-1 (0.08 in min-1), only the paratill was significantly greater (P = 0.006). A paratill operation in conjunction with conservation tillage could greatly decrease the potential for soil loss from winter wheat fields in the Palouse region. 

Keywords: Deep rip, infiltration rate, Palouse, paratill, water erosion

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Impact of subwatershed partitioning on modeled source- and transport-limited sediment yields in an agricultural nonpoint source pollution model 
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.2)

T.W. FitzHugh, D.S. Mackay 

ABSTRACT: Distributed parameter hydrologic models have a potential use as tools for supporting watershed management policy. However, proper model implementation will require an understanding of how to integrate data collection and models in watersheds that have differing characteristics. This study investigated the behavior of one such model, the Soil and Water Assessment Tool (SWAT), in relation to the level of spatial aggregation of input data and the extent to which the watershed is source- or transport-limited in terms of sediment yield. The approach here was to first test SWAT in an agricultural watershed in Southern Wisconsin. Then, a series of computer model applications were generated with a range of sediment source- and transport-limited conditions. SWAT was run for each watershed condition using eight watershed delineations, each with a different number of subwatersheds. Data aggregation affected model behavior differently depending on whether the watershed was sediment source-limited or transport-limited. This indicates that care is needed in selecting distributed sampling points, characterizing stream channel processes, and improving the selection of subwatershed sizes to match SWAT to watersheds with different characteristics. 

Keywords: Agriculture, geographic information systems, nonpoint sources, models, sediment transport, sediment yield

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Conservation management effects on soil erosion reduction in the Sichuan Basin, China 
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.2)

G. Liu, M.J. Lindstrom, X. Zhang, Y. Li, and J. Zhang 

ABSTRACT: Water erosion is a serious production problem in the Sichuan province of southwest China. Landscapes are topographically complex with slope gradients up to 40% used for crop production. The present recommended procedure for controlling soil erosion has been through terrace construction. However as slope gradients become greater than 10%, construction costs become prohibitive. Prior research has shown a reduction in water runoff and soil erosion using contour management. The objective of this study was to compare the effects of two contour management systems with the customary up and downslope tillage and planting (ST) on water runoff, soil erosion, and crop production. Experimental sites were established at five locations in Sichuan province. The two contour systems evaluated were a ridge and furrow system established every three years with a no-till planting on the ridge (CTN) for the summer crop and a ridge and furrow system established annually (CT) for the summer crop. The CTN treatment was more effective than CT in reducing water runoff (P = 0.05) at all locations but only significantly more effective in reducing soil erosion at three of the five sites. The contour management systems (CTN and CT) show a significant reduction in water runoff and soil erosion when compared to ST. An estimated practice (P) factor of 0.31 and 0.50 was calculated for the CTN and CT treatments. However, two of the five sites were still experiencing a high rate of soil erosion with contour management, indicating that further erosion control measures may be required. 

Keywords: China, contour management, Sichuan province, soil erosion, water runoff

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The effect of moldboard plow on tillage erosion along a hillslope
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.2)

D.V. St. Gerontidis, C. Kosmas, B. Detsis, M. Marathianou, T. Zafirious, and M. Tsara 

ABSTRACT: Tillage erosion is considered one of the most important processes of land degradation in hilly cultivated areas. Extensive cultivation of hilly areas have largely degraded soil in the past decades due to the erosion caused by use of heavy powerful tillage implements. In order to evaluate the effect of moldboard plow on tillage erosion, a study was conducted along an intensively cultivated hillslope (slope gradient from 6–22%) with rainfed crops. Two tillage experiments were carried out, one with the tillage implement moving perpendicular and the other parallel to the contour lines. The soil displacement by tillage was measured by using tracers (numbered aluminum cylinders of 1 cm3 volume) that were inserted into the soil at various depths at selected slope positions to give a range of slope gradients. Thirty strips were prepared and 1200 tracers were inserted into the soil for each experiment. The location of each tracer was precisely recorded using a theodolite before and after the tillage operation. Soil displacement was analyzed for three plow depths (20 cm, 30 cm, and 40 cm) and for two directions of tillage operation in each experiment. The effect of long term moldboard plowing on tillage erosion in the study hillslope was examined by using past and present detailed soil survey data, existing water erosion data, and empirical relationship data derived from this study. Downslope displacement of soil during tillage increased with increased plow depth and slope gradient. In steep hillslope positions (22% slope gradient), a maximum soil displacement of 97 cm was measured after plowing the soil downslope at the depth of 40 cm and perpendicular to the contour lines. After plowing the soil along contour lines, under the same soil conditions, and management practices, soil displacement was reduced to 69 cm. A 50% reduction in plow depth reduced soil displacement by more than 75%. The upslope reversion of furrow with the tractor moving parallel or perpendicular to the contour lines significantly reduced soil displacement, from 2–33 cm. The comparison of two tillage experiments showed that contour farming significantly decreased tillage erosion. The analysis of detailed soil survey data, water erosion data, and tillage erosion data demonstrated that tillage erosion was the most important process transporting soil from the upper convex to the lower concave parts of the study hillslope. 

Keywords: Moldboard plow, tillage erosion


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Effects of peanut cropping practices and canopy cover conditions on runoff and sediment yield 
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.2)

C.C. Truman and R.G. Williams 

ABSTRACT: Runoff and sediment yields were measured from eight field plots (40 m2) over a three year period to determine the effect of peanut cropping practices and canopy cover conditions on runoff and sediment loss. Plots were located on a Tifton loamy sand, and were exposed to four 30 min simulated rainfall sequences (I = 63.5 mm h-1 ) four to eight times per growing season. Runoff and sediment losses were measured from four soil cover conditions: continuous fallow, bare bedded, single row peanuts (Arachis hypogea L), and twin row peanuts (2 and 4 peanut rows per 2 m wide bed). Percent Cover (PC) and leaf area index (LAI) increased to a maximum then leveled off as plants matured or were harvested. PC for single and twin row peanuts was related to days since planting (DSP) (r = 0.96 for single row peanuts and r = 0.98 for twin row peanuts). LAI values for single and twin row peanuts were related to PC (r = 0.98 for single row peanuts and r = 0.94 for twin row peanuts). Single and twin row peanut plots had as much as eight times less runoff and as much as 63 times less sediment loss than continuous fallow or bare bedded plots. Twin row peanut plots had as much as three times less runoff and sediment loss than single row peanut plots. Sequence-based erodibility values calculated from continuous fallow plots (KFC) and bare bedded plots (KBB) ranged from 4–24 (3 yr mean = 11.3, s.d. = 5.3) and 2–36 kg ha h MJ-1 ha-1 mm-1 (3 yr mean = 12.9, s.d. = 11.6), respectively. Soil loss ratios (SLR) ranged from 0.01–2.61. SLRs decreased to a low for cropstage 3 when percent canopy cover was greatest (DSP = 81–107), then increased as peanut plants matured or were harvested. Results show how management practices, such as twin row peanuts, can maximize peanut canopy development early in the growing season and minimize the time in which bare soil is vulnerable to a runoff producing rainstorm, thus reducing runoff and soil loss and conserving valuable natural resources. 

Keywords: Cover factor, crop canopy, rainfall simulation, RUSLE, southeastern U.S., USLE

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Small grain cover crops and wheel traffic effects on infiltration, runoff, and erosion 
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.2)

T.C. Kaspar, J.K. Radke, and J.M. Laflen 

ABSTRACT: Oat and rye cover crops have the potential to reduce erosion when following soybean crops in Iowa. Oat and rye cover crops were overseeded into no-till soybeans in August of 1995, 1996, and 1997 on a sloping site. Infiltration, runoff, and interrill erosion were measured in April of 1996, 1997, and 1998 using an oscillating sprinkler head rainfall simulator that applied water at approximately 125 mm hr-1. Rill erosion was measured by making flow additions to the upslope end of plots. All measurements were made concurrently on tracked and untracked interrows. Cover crops had no effect on infiltration and erosion in 1996. In 1997, both oat and rye cover crops reduced interrill erosion, but in 1998 only rye increased infiltration and reduced interrill erosion and runoff. Untracked interrows had less interrill erosion and runoff, and more infiltration than tracked interrows. In 1997 and 1998, both oat and rye cover crops reduced rill erosion, but wheel traffic had no measurable effect on rill erosion. 

Keywords: Cover crops, erosion, infiltration, interrill, no-till, rainfall simulator, residue cover, rill, runoff, sediment

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Soil selection for use in environmental analysis 
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.2)

C. Arndt, B. Fecso, P. V. Preckel, B. Stoneman 

ABSTRACT: Estimating variables, such as erosion rates, across a diverse soil and water resource base is a problem of interest in natural resource management. Here, we propose an alternative to the predominant soils (PS) approach of Stoneman, Brown, and Spivey. Our method, called Gaussian quadrature (GQ), is adapted from the numerical integration literature. Two experiments compare GQ with PS. The first plugs sample input into a simulation model to approximate erosion rates, surface runoff, and crop yield for a region. The second estimates erosion in three regions using the Universal Soil Loss Equation (USLE). Results for the GQ samples are compared to results for the full population and results from random samples. GQ sampling tends to be more effective, particularly with respect to measures related to the heterogeneity of the population, such as the  variance and skewness, than PS or random sampling. Judiciously used, GQ sample selection permits reductions in the number of soils sampled with only a moderate loss of accuracy. 

Keywords: Gaussian quadrature, sampling, soil sampling, statistical subset


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