July - August 2003: Volume 58, Number 4
Table of Contents
Features
- The best buildings can’t be seen
By Carol Steinfeld
- Far out environmental monitoring
By Sharon Guynup and Nicolas Ruggia
- Assuring accountability
By Andrew P. Manale
Research Editorials
- Soil quality: Humankind’s foundation for survival [PDF of complete article available]
D.L. Karlen, J.W. Doran, B.J. Weinhold, and S.S. Andrews
- Deficiencies in the soil quality concept and its application [PDF of complete article available]
J. Letey, R.E. Sojka, D.R. Upchurch, D.K. Cassel, K.R. Olson, W.A. Payne, S.E. Petrie, G.H. Price, R.J. Reginato, H.D. Scott, P.J. Smethurst, and G.B. Triplett
Research
Departments
- Home Front
- Viewpoint--Jeffrey Zinn, senior analyst at the Congressional Research Service
- Raise Your Voice
- Notebook
- Conservogram
Soil quality: Humankind’s foundation for survival
(Full text appears in the Journal of Soil and Water Conservation, Vol.58, No. 4)
Full text available in PDF by clicking on this link.
D.L. Karlen, J.W. Doran, B.J. Weinhold, and S.S. Andrews
ABSTRACT: During the past decade, soil quality research and education programs have increased exponentially throughout the world. Educational and assessment approaches, ranging from simple scorecard and test-kit monitoring to comprehensive quantitative assessments and indexing using soils databases, have been pursued. The programs have emphasized that soil quality is not "an end in itself" but rather a tool for evaluating and understanding the effects of soil management on a specific soil resource. The approaches have stressed that to determine how well a soil is functioning, inherent and dynamic soil properties and processes must be evaluated using biological, chemical, and physical indicators. No soil quality researcher has ever envisioned the concept would replace modern soil survey programs or diminish the importance of scientifically based soil management strategies. Herein, we present the scientific merits of soil quality research.
Keywords: Soil health, soil management, soil rating for plant growth model (SRPG), soil resource assessment, soil tilth, sustainable agriculture
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Deficiencies in the soil quality concept and its application
(Full text appears in the Journal of Soil and Water Conservation, Vol.58, No. 4)
A PDF version of the full text can be printed by clicking this link.
J. Letey, R.E. Sojka, D.R. Upchurch, D.K. Cassel, K.R. Olson, W.A. Payne, S.E. Petrie, G.H. Price, R.J. Reginato, H.D. Scott, P.J. Smethurst, and G.B. Triplett
ABSTRACT: Soil quality is a concept that has deeply divided the soil science community. It has been institutionalized and advocated without full consideration of concept weaknesses and contradictions. Our paper highlights its disfunctional definition, flawed approach to quantification, and failure to integrate simultaneous functions, which often require contradictory soil properties and/or management. While the concept arose from a call to protect the environment and sustain the soil resource, soil quality indexing as implemented may actually impair some soil functions, environmental quality, or other societal priorities. We offer the alternative view that emphasis on known principles of soil management is a better expenditure of limited resources for soil stewardship than developing and deploying subjective indices which fail to integrate across the necessary spectrum of management outcomes. If the soil quality concept is retained, we suggest precisely specifying soil use, not function or capacity, as the criteria for attribute evaluation. Emphasis should be directed toward using available technical information to motivate and educate farmers on management practices that optimize the combined goals of high crop production, low environmental degradation, and a sustained resource.
Keywords: Environment, land use, landscape, soil condition, soil fertility, soil health, soil organic matter, soil properties, soil quality index, water quality
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Watershed-lake water quality modeling: Verification and application
(Full text appears in the Journal of Soil and Water Conservation, Vol.58, No. 4)
K.R. Mankin, S.H. Wang, J.K. Koelliker, D.G. Huggins, and F. deNoyelles
ABSTRACT: Water quality degradation in many Central Plains reservoirs results from a combination of lake morphology and watershed characteristics. This leads to high rates of eutrophication, sedimentation and related problems. This study coupled two models—Agricultural Nonpoint Source (AGNPS) watershed and BATHTUB lake—to simulate actual lake water quality conditions in three contrasting subbasins and subwatersheds of Clinton Lake, Kansas, and demonstrated the use of the coupled model for simulating lake response to changes in watershed land use and management. Watershed event-based yields were used to determine monthly watershed loads of water, sediment, nitrogen (N), and phosphorus (P) to Clinton Lake. The lake was initially surveyed for depth and sampled monthly for various water-quality parameters with depth at 12 sites from May through December 1997 and April through November 1998. Watershed loads for 1997 conditions (26.5% cropland, 56.0% grassland) accurately simulates lake levels of total N, total P, chlorophyll a (chl a), and Secchi depth for each subbasin. The calibrated model simulated in-lake reductions as much as 35% for N, 38% for P, and 49% for chl a from the native-grass scenario, and increases as much as 6% for N, 12% for P and 9% for chl a from removing all existing terraces (17.8% of watershed). The calibrated current-conditions model also demonstrated a decrease in N:P ratio from 9.3 to 8.7 as lake depth decreased from sedimentation over the next century. The coupled model shows promise for load allocation and lake water-quality response determinations to support the total maximum daily load (TMDL) process.
Keywords: Eutrophication, lake modeling, sedimentation, TMDL, watershed management, watershed modeling
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Optimizing the placement of riparian practices in a watershed using terrain analysis
(Full text appears in the Journal of Soil and Water Conservation, Vol.58, No. 4)
M.D. Tomer, D.E. James, and T.M. Isenhart
ABSTRACT: Riparian buffers and constructed wetlands are best management practices (BMPs) that can improve water quality. However, these practices are not equally effective in all locations. Our objective was to develop maps to help plan the placement of BMPs in a watershed for water quality benefits. Tipton Creek, a 49,000-acre Iowa watershed, provided a case study. Buffer-placement maps, developed from analysis of 30-m (100-ft) elevation data, identified riparian locations with large wetness indices, where buffer vegetation could intercept sheet/rill flows from significant upslope areas. These sites were numerous, typically small (<200 m in length) and well distributed spatially. However results showed 57% of riparian grid-cells would receive runoff from less than 0.4 ha (1 ac). Candidate wetland sites were also mapped by applying interpretive and automated techniques to terrain analyses results. A team of conservation professionals evaluated the planning utility of these maps in the field through consensus-seeking discussion. Buffer maps highlighted areas where, team members agreed, perennial vegetation could effectively intercept runoff and/or manage seasonal wetness. The review team also located three feasible wetland sites, which were all identified by an automated technique showing 12 candidate sites. The methods only required public data and should be applicable to other watersheds.
Keywords: Best management practices, conservation planning, Conservation Reserve Enhancement Program, constructed wetlands, riparian buffers, watershed management
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Ammonia volatization trends following liquid hog manure application to forage land
(Full text appears in the Journal of Soil and Water Conservation, Vol.58, No. 4)
B.D. Lambert and E.W. Bork
ABSTRACT: Recent changes in the livestock industry of western Canada have included the increased establishment of intensive hog operations in semi-arid regions where the availability of cultivated land for manure disposal is limited. Instead, permanent forage lands, including both tame pasture and native rangeland, are being considered for manure application. Given the inability of manure to be incorporated on these areas with cultivation, this study tested and successfully utilized static sorber traps as a relatively easy and inexpensive method to assess ammonia (NH3) losses on forage lands following different rates and methods of liquid hog manure application. Comparisons among treatments indicated ammonia loss increased with rate of manure application, with relatively greater losses on tame pasture than native rangeland. Coulter injection resulted in less ammonia loss compared to surface banding, with the greatest benefit on tame pastures, presumably due to the lack of surface litter and associated abundance of bare soil, factors that would increase ammonia volatilization. We conclude that the use of injection is beneficial in reducing ammonia loss on forage lands, particularly tame pastures at greater rates of manure application, but concede the economic benefits based on the amount of nitrogen conserved may be limited.
Keywords: Ammonia, forage land, hog manure, injection, litter, rangeland, static sorber traps, surface banding
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Fifty years of crop evapotranspiration studies in Puerto Rico
(Full text appears in the Journal of Soil and Water Conservation, Vol.58, No. 4)
E.W. Harmsen
ABSTRACT: The water resources of Puerto Rico are currently being threatened by population pressure, development, pollution, and potentially adverse changes in the climate. Accurate determination of evapotranspiration is essential in managing water resources and practicing water conservation in Puerto Rico. In support of this goal, a review is presented covering the majority of research on crop water use and evapotranspiration estimation methods used in Puerto Rico during the last fifty years. Specifically, the review considers consumptive use determined from field water balance studies, calculation methods, and the pan evaporation method. Several studies also considered the estimation of reference evapotranspiration and
the procedures for estimating climate parameter data needed as input to the reference evapotranspiration calculation methods. Recommendations for research priorities are provided.
Keywords: Crop water use, evapotranspiration, Hargreaves-Samani, pan evaporation, Penman-Monteith, Puerto Rico, reference evapotranspiration, U.S. Department of Agriculture-Soil Conservation Service (USDA-SCS) Blaney-Criddle
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