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A data set comprising rainfall-runoff data gathered at 31 Agricultural Research Service experimental watersheds was used to explore curve number calibration. This exploration focused on the calibrated value and goodness-of-fit as a function of several items: calibration approach, precipitation event threshold, data ordering approach, and initial abstraction value. Calibration methods explored were least-squares, the National Engineering Handbook (NEH) median, and an asymptotic approach. Results were quantified for events exceeding two precipitation thresholds: 0 and 25.4 mm. Natural and frequency-matched data ordering methods were analyzed. Initial abstraction ratios of 0.05 and 0.20 were examined. Findings showed that the least-squares calibration approach applied directly to rainfall-runoff data performed best. Initial abstraction ratios clearly influenced the magnitude of the calibrated curve number. However, neither ratio outperformed the other in terms of goodness-of-fit of predicted runoff to observed runoff. Precipitation threshold experiments produced mixed results, with neither threshold level producing a clearly superior model fit. Frequency-matching was not considered to be a valid analysis approach, but was contrasted with naturally ordered results, indicating a bias toward producing calibrated curve numbers that were 5–10 points larger. [ABSTRACT FROM AUTHOR]

He makes a valid point that the HT ht measure does not capture this. Our calibration process entailed first determining a CN value for every HT ht observation. We believe the discusser is stating that large HT ht values may influence the calibration more than small HT ht values. [Extracted from the article]

A study was initiated to investigate the sustainability effects of intercropping switchgrass (Panicum virgatum L.) in a loblolly pine (Pinus taeda L.) plantation. This forest-based biofuel system could possibly provide biomass from the perennial energy grass while maintaining the economics and environmental benefits of a forest managed for sawtimber. Operations necessary for successful switchgrass establishment and growth, such as site preparation, planting, fertilizing, mowing and baling, may affect hydrology and nutrient runoff. The objectives of this study were (i) to characterize the temporal effects of management on nutrient concentrations and loadings and (ii) to use pretreatment data to predict those treatment effects. The study watersheds (~25 ha each) in the North Carolina Atlantic Coastal Plain were a pine/switchgrass intercropped site (D1), a midrotation thinned pine site with natural understory (D2), and a switchgrass-only site (D3). Rainfall, drainage, water table elevation, nitrogen (total Kjedahl N, NH4-N, and NO3-N), and phosphate were monitored for the 2007-2008 pretreatment and the 2009-2012 treatment periods. From 2010 to 2011 in site D1, the average NO3-N concentration effects decreased from 0.18 to -0.09 mg L-1, and loads effects decreased from 0.86 to 0.49 kg ha-1. During the same period in site D3, the average NO3-N concentration effects increased from 0.03 to 0.09 mg L-1, and loads effects increased from -0.26 to 1.24 kg ha-1. This study shows the importance of considering water quality effects associated with intensive management operations required for switchgrass establishment or other novel forest-based biofuel systems. [ABSTRACT FROM AUTHOR]

Paired watershed studies have historically been used to quantify hydrologic effects of land use and management practices by concurrently monitoring two neighboring watersheds (a control and a treatment) during the calibration (pre-treatment) and posttreatment periods. This study characterizes seasonal water table and flow response to rainfall during the calibration period and tests a change detection technique of moving sums of recursive residuals (MOSUM) to select calibration periods for each control-treatment watershed pair when the regression coefficients for daily water table elevation (WTE) were most stable to reduce regression model uncertainty. The control and treatment watersheds included 1-3 year intensively managed loblolly pine (Pinus taeda L.) with natural understory, same age loblolly pine intercropped with switchgrass (Panicum virgatum), 14-15 year thinned loblolly pine with natural understory (control), and switchgrass only. Although monitoring during the calibration period spanned 2009 to 2012, silvicultural operational practices that occurred during this period such as harvesting of existing stand and site preparation for pine and switchgrass establishment may have acted as external factors, potentially shifting hydrologic calibration relationships between control and treatment watersheds. Results indicated that MOSUM was able to detect significant changes in regression parameters for WTE due to silvicultural operations. This approach also minimized uncertainty of calibration relationships which could otherwise mask marginal treatment effects. All calibration relationships developed using this MOSUM method were quantifiable, strong, and consistent with Nash-Sutcliffe Efficiency (NSE) greater than 0.97 for WTE and NSE greater than 0.92 for daily flow, indicating its applicability for choosing calibration periods of paired watershed studies. [ABSTRACT FROM AUTHOR]

This article introduces a collection of papers from the third biennial ASABE 21st Century Watershed Technology Conference and Workshop: Improving Water Quality and the Environment, held in Bari, Italy, on 26-31 May 2012. This Special Collection consists of seven articles (plus one published previously) selected from the 59 meeting papers. The technical presentations at the conference focused on solving spatial and temporal water quality and quantity problems and addressed topics such as watershed management in developing countries, water quality standards, agricultural best management practice (BMP) effectiveness, emerging problems, impact of extreme weather conditions, biological monitoring, increasing stakeholder involvement, political and economic implications, watershed implementation planning, forest and rangeland water quality issues, and water resources education. At first glance, these topics seem quite diverse. However, a growing trend in cutting-edge hydrological science research, and a thread that emerged from these papers, is that of "data mining." In this article, we make an editorial statement that briefly introduces the basic principles of data mining and uses this concept as an organizing theme to feature eight articles of this Special Collection. [ABSTRACT FROM AUTHOR]

A microwave dielectric method was used for nondestructive and rapid determination of moisture content in shelled and unshelled peanuts of various types from transmission measurements of their relative complex permittivities in free space at 23° C between 5 and 15 GHz. Moisture content was estimated, independent of bulk density, with three density-independent calibration functions and compared to standard oven moisture determinations; two of these functions are permittivity-based, and the other is expressed in terms of attenuation and phase shift. The effectiveness and stability of these three functions for type independence were evaluated over broad ranges of frequency, moisture content, and bulk density. While the performance of each function with individual type calibrations was reaffirmed, statistical analysis also showed high coefficients of determination in predictions with the combined type-independent calibrations. Therefore, with microwave moisture sensing technology, calibration equations can be used to accurately predict moisture content in peanuts with insensitivity to type; which is a characteristic lacking in today's commercial moisture meters. [ABSTRACT FROM AUTHOR]

Polymeric films and fibers are used extensively in industrial and personal products. Many of these products are intended to be disposable and, after initial use, are disposed in landfills that are increasingly expensive and limited. Proprietary additives are being promoted to enhance the biodegradation of polypropylene (PP) and related materials. A test was run on samples of diapers containing PP in simulated landfills and in convection ovens over a period of 52 weeks. Samples in the oven treatment lost all strength properties in less than 27 weeks. Back sheet and cuff samples in the landfill lost insignificant (P<0.05) strength under landfill conditions over 52 weeks. Statistics show significant differences (P<0.05) in strength and sample percent elongation during testing for time, temperature, and time-temperature interactions for both the oven and landfill tests. The study led to the conclusion that the polypropylene additive was efficacious for programmable destruction in an oxidative environment but not efficacious in an anaerobic environment. [ABSTRACT FROM AUTHOR]

A flume study was conducted using a soil, yard waste compost, and an erosion control compost to investigate the response to concentrated flow and determine if the shear stress model could be used to describe the response. Yard waste compost (YWC) and the bare Cecil soil (CS) control responded to concentrated laboratory runoff similarly in rill formation, and the shear stress model was useful in estimating sediment yields from both of these land covers. Results indicated that critical shear stress values for yard waste compost and Cecil soil were not significantly different. However, the erodibility of the soil was higher, resulting in increased solids loss, on the Cecil soil. Micro-dams, the main mechanism for limiting soil erosion for the compost, often occurred in the rills of the erosion control compost (ECC), causing the concentrated flow to infiltrate and fan out through the compost. Since flow could not be maintained in the rill, parameters for the stress model could not be determined for the erosion control compost. [ABSTRACT FROM AUTHOR]

Various methods are used to estimate sediment transport through riparian buffers and grass filters, with the sediment delivery ratio having been the most widely applied. The U.S. Forest Service developed a sediment delivery ratio using the stiff diagram and a logistic curve to integrate some of the factors influencing sediment delivery heuristically. This study independently tested the Forest Service sediment delivery ratio contrasted with artificial neural networks to represent the multiple nonlinearities between important factors and sediment delivery. The Forest Service sediment delivery ratio was not adequate when compared to published sediment yields from 30 small experimental buffers from three countries, including four forested buffers. However, artificial neural networks gave estimates of the delivery ratio that were highly correlated to the observations. The 30 buffer observations produced such good estimates of the sediment delivery ratio with both seven and five buffer parameters that this study suggests that as few as 30 sediment yield observations can be the basis for applying neural networks to interpolate the complex, multiple nonlinearities of hydrology and sediment transport on riparian buffers. [ABSTRACT FROM AUTHOR]

Flow regime and total suspended solids (TSS), along with chemical and biological parameters associated with urbanization and intensive agriculture/aquaculture, impact benthic organisms, which represents the food chain foundation in aquatic systems. We designed this experiment to begin the integration of physical flow regime effects along with chemical and biological indicators on periphyton, an important benthic organism indicator, towards a goal of using periphyton (live biomass containing chlorophyll a) and pheophytin (dead chlorophyll-containing biomass) in assessments of stream health. Physical flow regimes in a laboratory flume were created using multiple roughness conditions and an in-channel weir Results suggested that one could model the hydraulic regime with a hydraulic model, HEC-RAS, to within 2% to 11% of measured velocity values. Thus, one may roughly but not precisely move computed velocities from the flume to the field. Significant interactions between biological response and hydraulic and TSS factors were observed, and the study suggested several indicators of periphyton-pheophytin response that are potentially relevant to ecological engineering applications featuring a channel. Increased mean velocities significantly reduced (P < 0.05) live periphyton and filament length. The 200 mg L-1 TSS level significantly reduced (P < 0.05) biomass and filament development. The effect of TSS was least where velocity was highest and depth was most shallow, which had the least effect on light absorption and resulted in the least sediment deposition. The intermediate TSS level (100 mg L-1) appeared to stimulate a growth response based on periphyton and filament length, although the effect was less noticeable where velocities were higher. Pheophytin tended to be highest in conditions resulting in lower periphyton values, consistent with the notion that regimes imparting physical stress would harbor the highest concentration of pheophytin. The periphyton/filament length ratio tended to be lowest in velocities less than O. 75 m s-1 except in the high TSS case, where both periphyton and filament length were low. Low velocities and low to moderate TSS would provide the most biomass for grazing organisms and would result in the most effective nutrient filtering due to long filament length. High periphyton/pheophytin ratios were associated with high TSS, velocities exceeding ∼0.5 m s-1, or both. Sloughing could occur in systems with a pulsing velocity where the pulse period was long enough for growth to occur in the quiescent interval. [ABSTRACT FROM AUTHOR]

This study evaluated fluctuations in the output signal of a densimeter, an in situ suspended-sediment measurement device based on a very sensitive differential pressure transducer. Although the densimeter produced accurate (less than 10% error) results in the laboratory for concentrations of 10–1,000 mg/L, there was a much larger fluctuation in the field test output signal. These fluctuations were hypothesized to have originated from fluctuations imparted by movement of bed material on the channel bottom. Measuring root mean square and mean velocities and corresponding pressure differences at locations in front of and behind a bluff body simulated movement of a body/bed form past a sampling point in a quasistatic manner. Position of the bluff body relative to the sample port resulted in differential pressure swings equivalent to 65,000 mg/L sediment concentration. Turbulent structure changed dramatically with position of the bluff body. Thus, pressure densitometry using a differential pressure transducer is likely not a reliable system for measuring sediment concentration under in-stream conditions, particularly near the channel bottom where bed forms and large objects may pass between the sample ports. [ABSTRACT FROM AUTHOR]

Presents a study that evaluated the performance of a laboratory-developed process and characterized the differences between composting during fall and winter conditions. Potential for the bioconversion of solid wastes from the pulp and paper industry into a beneficial product; Viability of the product as a soil conditioner; Information on the paper mill by-products.

Over 70% of solid wastes (by-products) generated in the manufacture of paper pulp are presently disposed of in landfills. Most of these by-products are compostable and reusable in horticulture, landscaping and agriculture. This work addresses the questions of nitrogen amendments required for composting a mix of four bleached kraft pulp mill by-products -- namely, primary sludge, bark, grit and ash. Two nitrogen amendments, ammonium nitrate and chicken litter were compared to determine which provided a more rapid mass reduction and stabilization. Different amounts of ammonium nitrate addition were evaluated to determine if decreasing the C: N ratio of the initial mix (from 130.9 to 28.3) resulted in more rapid composting. A blend of sludge, grit, bark and ash in dry weight percentages of 56, 25, 6 and 13% respectively, stabilized (measured using oxygen respirometry) in a period of 28 days. Although in the initial stages of composting there were differences resulting from the effect of the two types of nitrogen amendments, at the 28th day no significant difference was observed. It was also found that decreasing the C:N ratio did not accelerate the composting process. A composting mix with a C:N ratio of 130.9 had similar mass reduction compared to others with C:N of 95.3, 79.5 and 28.3. Lower C:N ratios were in fact less preferable because of high soluble salt content and greater amendment requirements. [ABSTRACT FROM AUTHOR]

Presents information on a study which examined the advances in the development of sensors and controllers for agricultural applications. Control objective in a farming operation; Sensing systems leading to real-time control or field mapping; Controllers in agricultural equipment.

Spatial and statistical variability in soil characteristics must be addressed in using soil testing to guide precision nutrient management. This paper provides a case study comparing strategies using technology currently available and economically viable for farmers or their advisors to use for this purpose. The first strategy is to divide a large area into smaller subunits for sampling, then to map results by assigning the soil test value for each sample to the entire subunit, resulting in a mosaic of soil test values across the entire sampling area. An alternative approach involves collecting soil samples from known locations using global positioning system (GPS) technology, then mapping the spatial distribution of soil test results. The final strategy is to use the cumulative distribution function (CDF) to find the percentage of samples with soil test values at or below certain levels irrespective of their location. Based on 72 soil samples from a highly variable 40 ha research site, we found that inaccuracy of GPS may limit its application. Maps communicate soil test results readily, but may be difficult to apply in fertilizer management. The CDF approach provides useful information, but interpreting and applying the information may be difficult. Any of these methods of assessing soil test variability will require analysis of far more samples than composite sampling, and the value of the added information must justify increased analytical costs. [ABSTRACT FROM PUBLISHER]

Although water retention and movement in soils determine both the need for irrigation and the loss of nitrogen (N) from agricultural systems, soil physical tests are generally too time‐consuming for routine analysis by soil testing laboratories. We evaluated the potential of the Moisture Equivalent (ME) method as described by Bouyoucos for routine soil physical measurement. The method consists of saturating a sieved soil sample in a Buchner funnel, vacuum filtering the sample for 15 min while covered, then determining the gravimetric water content. On 72 soil samples run in triplicate, ME results were highly repeatable (CV values generally less than 3%). In addition, ME results were linearly correlated to clay and organic matter contents (R2 = 0.85) and to 33 kPa moisture content (R2 = 0.85). We conclude that the ME method is sufficiently convenient to run routinely in a soil testing laboratory, and sufficiently dependable to improve precision in irrigation and N management. Interpretive criteria for applying ME results will require verification through field calibration studies. [ABSTRACT FROM PUBLISHER]

This article introduces the five papers in the "International Watershed Technology" collection. These papers were selected from 60 technical presentations at the fifth biennial ASABE 21st Century Watershed Technology Conference and Workshop: Improving the Quality of Water Resources at Local, Basin, and Regional Scales, held in Quito, Ecuador, on 3-9 December 2016. The conference focused on solving spatial and temporal water quality and quantity problems and addressed topics such as watershed management in developing countries, aquatic ecology and ecohydrology, ecosystem services, climate change mitigation strategies, flood forecasting, remote sensing, and water resource policy and management. While diverse, the presentation topics reflected the continuing evolution of the "data mining" and "big data" themes of past conferences related to geospatial data applications, with increasing emphasis on practical solutions. The papers selected for this collection represent applications of spatial data analyses toward practical ends with a theme of "tools and techniques for sustainability." The papers address a range of topics, including the matching of crops with water availability, and assessing the environmental impacts of agricultural production. The papers identify some of the latest tools and techniques for improving sustainability in watershed resource management that are relevant to both developing and developed countries. [ABSTRACT FROM AUTHOR]

This article introduces a collection of papers from the fourth biennial ASABE 21st Century Watershed Technology Conference and Workshop: Improving Water Quality and the Environment, held in Hamilton, New Zealand, on November 3-6, 2014. This Special Collection consists of three articles selected from the 47 meeting papers. The technical presentations at the conference focused on solving spatial and temporal water quality and quantity problems and addressed topics such as watershed management in developing countries, water quality standards, agricultural best management practice (BMP) effectiveness, emerging problems, impact of extreme weather conditions, biological monitoring, increasing stakeholder involvement, political and economic implications, watershed implementation planning, forest and rangeland water quality issues, and water resources education. At first glance, these topics seem quite diverse. A more detailed look suggested that the "big data" and data mining themes of the last conference in Bari, Italy, continued to develop. [ABSTRACT FROM AUTHOR]

An accurate determination of soil hardpan location is important for maximum precision tillage performance. Cone penetrometers are often used to locate hardpans in soils. This determination in layered soils is more complex due to the complexity of soil reaction to cone penetration. An axisymmetric finite element (FE) model was developed to simulate cone penetration for the prediction of the hardpan location in a layered Norfolk sandy loam soil The soil was considered as a non-linear elastic-plastic material, and it was modeled using a Drucker-Prager model with the Hardening option in ABAQUS, a commercially available FE package. ABAQUS/Explicit was used to simulate soil-cone contact pair interaction. The results showed that the FE model captured the penetration resistance trend with two deflection points indicating the start of the hardpan and the peak cone penetration resistance. The FE-predicted results showed the hardpan at a depth of 7.29 cm compared to 11.08 cm from cone penetration tests. Soil moisture, bulk density, and cone surface conditions significantly affected the predicted and experimental results. The simulation also showed soil deformation zones about 3 times the diameter of the cone that developed around the advancing cone. [ABSTRACT FROM AUTHOR]