Showing papers in "Transactions of the ASABE in 1988"
TL;DR: In this article, the relationship between topographic attributes and the distribution of surface soil water content in a small bare-fallow cultivated catchment was examined and the most statistically significant regression equations describing this relationship contained the independent topographic variable aspect and the compound variable ln(A), where A,=Ab/S and A^ is the local upslope contributing area per unit width of contour line and S is the slope The index ln, a measure of soil saturation, and the product of A^ and S (A^S) were both capable of predicting
Abstract: THE relationship between topographic attributes and the distribution of surface soil water content in a small bare-fallow cultivated catchment was examined The most statistically significant regression equations describing this relationship contained the independent topographic variable aspect and the compound variable ln(A,), where A,=Ab/S and A^ is the local upslope contributing area per unit width of contour line and S is the slope The index ln(A,), a measure of soil saturation, and the product of A^ and S (A^S), a measure of the erosive power of concentrated surface runoff, were both capable of predicting the location of ephemeral gullies in certain parts of the catchment However, combining them produced even better predictions throughout the catchment Ephemeral gully locations were predicted in areas where the topographic indice ln(Ab/S) was greater than 68 and A^S was greater than 18 These results demonstrate that topographic nonuniformity within small catchments is a major factor controlling the spatial variability of soil water and the location and development of ephemeral gullies
389 citations
TL;DR: In this paper, the spectral data with photosynthetic quantum yield and phytochrome photochemical cross-sections were used as indicators of the photostationary state determined by a radiation source.
Abstract: SPECTRAL data provides the information to quantify the photosynthetic and morphogenic responses of plants to a specific radiation environment. The mathematical products of spectral data with photosynthetic quantum yield and phytochrome photochemical cross-sections were used as indicators of the photosynthetic efficiency and phytochrome photostationary state determined by a radiation source.
357 citations
TL;DR: In this article, first and third cutting alfalfa was ensiled in mini-silos (100 ml centrifuge tubes) at 40 or 55% dry matter and incubated at 15, 25 or 35 °C for 40 days.
Abstract: FIRST and third cutting alfalfa was ensiled in mini-silos (100 ml centrifuge tubes) at 40 or 55% dry matter and incubated at 15, 25 or 35 °C for 40 days. In both trials and at both dry matter levels, the amount of proteolysis increased with storage temperature, averaging 10 percentage units as a fraction of total nitrogen between 15 and 35 °C. Increasing storage temperature also elevated ammonia concentrations between 15 and 25 °C but not between 25 and 35 °C. The results of this study indicated that temperature affected the rate of loss of protease activity during fermentation, based on simulations using the silage model of Pitt et al. (1985) as modified by Muck (1987). The experiments suggest that management practices that control or reduce silage temperature may be important in maximizing the amount of nitrogen in alfalfa which remains as true protein through ensiling.
200 citations
TL;DR: In this paper, field experiments were conducted to study the effects of no-till and conventional tillage, and single and slit N-fertilizer applications, for continuous corn production on the leaching of nitrate-nitrogen (NO3-N) through subsurface drainage water and below the root zone.
Abstract: FIELD experiments were conducted to study the effects of no-till and conventional tillage, and single and slit N-fertilizer applications, for continuous corn production on the leaching of nitrate-nitrogen (NO3-N) through subsurface drainage water and below the root zone. The comparison between conventional and no-till was made by applying a single application of 175 kg-N/ha at the time of planting, and the comparison between single and split N applications was made for the no-tillage system. Six experimental plots, each drained with a single subsurface drain, were intercepted by installing sumps for measuring drain flow rates and collecting drainage water samples for NO3-N analyses. Also, four sets of piezometers were installed for deep water sampling. In the first year of the experiments, tillage and N-fertilizer management schemes did not significantly affect NO3-N concentrations in drainage. However, in the third year, the average NO3-N concentrations in drainage from conventional tillage plots were significantly greater than those of no-till plots when a single application of 175 kg-N/ha was made. The results of this study indicate that split N-applications totaling 125 kg/ha reduced NO3-N concentrations in drainage compared with a single, higher rate of application of 175 kg/ha for the no-tillage treatment.
165 citations
TL;DR: In this article, four large, weighing, monolithic lysimeters were designed, constructed and installed at Bushland, TX and each lysimeter has a surface area of 9 m^ and a soil depth of 2.3 m. Each soil monolith has a mass of approximately 45 Mg, including the container mass.
Abstract: FOUR large, weighing, monolithic lysimeters were designed, constructed and installed at Bushland, TX. Each lysimeter has a surface area of 9 m^ and a soil depth of 2.3 m. The soil within each lysimeter is an undisturbed monolith of Pullman clay loam. Each soil monolith has a mass of approximately 45 Mg, including the container mass. The lysimeters are installed in a 20 ha field with one lysimeter located in the center of each quarter of the field. The parameters of wind disturbance, water infiltration, drainage, thermal continuity, sidewall water percolation, rooting depth, scale stability, row spacing geometry, and safety were considered in the design. A compact mechanical type weighing system and load cell was used with an overall capability of detecting mass changes equivalent to a minimum of 0.05 mm of water. Automated data acquisition and telecommunication to offsite computers were utilized.
130 citations
TL;DR: In this article, two models were developed to predict the respiration rate of tomatoes stored under controlled atmosphere conditions, i.e., O2 and CO2 concentrations of 5 to 20%, respectively.
Abstract: TOMATOES were stored under 20 gas environments involving O2 and CO2 concentration of 5 to 20%, respectively. Two models were developed to predict the respiration rate of tomatoes stored under controlled atmosphere conditions. Although Model-II was found to be slightly better than Model-1, Model-1 was simpler to use. O2 concentration was observed to have more pronounced effect than the CO2 concentration on the firmness of tomatoes. Tomatoes stored at 21 °C and under 5% O2 and 5 to 15% CO2 gas environments for up to 45 days had no significantly different off-flavor than tomatoes stored at 12 °C under ambient conditions.
105 citations
TL;DR: In this paper, the sizes of aerial starch, grain meal and all particles present in swine finishing houses were described by the log normal distribution and the respirable fractions by mass and by number were 3.7 and 76.1%, respectively.
Abstract: THE sizes of aerial starch, grain meal and all particles present in swine finishing houses were described by the log normal distribution. Respirable fractions by mass and by number were 3.7 and 76.1%, respectively, as estimated from the particle size distribution. Most starch and grain meal particles identified were larger than 5 jum diameter. Fifty percent of all particles were less than 2.6 jLtm diameter. Higher total mass concentrations were not associated with similar increases in respirable mass concentrations. The aerial dust originated primarily from feed, based on particle identification using optical and electron scanning microscopy.
81 citations
TL;DR: In this paper, the performance of a direct injection diesel engine operating on mechanically expelled-unrefined soybean oil and sunflower oil blended with number 2 diesel fuel on a 25:75 v/v basis was evaluated.
Abstract: THE performance of a direct injection diesel engine operating on mechanically expelled-unrefined soybean oil and sunflower oil blended with number 2 diesel fuel on a 25:75 v/v basis was evaluated. The power remained constant throughout 200 h of operation. Excessive carbon deposits on all combustion chamber parts precludes the use of these fuel blends, at least in this engine and under the specified EMA operating conditions.
81 citations
TL;DR: In this paper, the response of corn to naturally fluctuating water tables at five different stages of growth was studied for three years, and the results of these studies indicate that SEW30 values of as low as 40 cm-days in the early part of the growing season can significantly reduce corn yields.
Abstract: THE response of corn to naturally fluctuating water tables at five different stages of growth was studied for 3 years. Fifty plots of 15 m x 15 m were established in 1984 on Nicollet soil in an area that is not artificially drained. In the center of each plot, an observation well was installed for water-table measurements. Water-table hydrographs were developed for each plot annually to quantify crop stress factors from excessive wetness (SEW30, a summation of days times the height of the water table above 30 cm). The results of these studies indicate that SEW30 values of as low as 40 cm-days in the early part of the growing season can significantly reduce corn yields. Corn yields decreased linearly with the increase in SEW30 values and the Stress Day Index (SDI). Lower corn yields resulted from both decreased plant population and poor crop growth due to excessive wetness.
80 citations
TL;DR: In this article, a programmable rainfall simulator was used to study the effects of variable intensity storm patterns on infiltration, runoff, and erosion when rain was applied to an initially dry soil, peak runoff rates were four to 20 times greater from storms having maximum intensities occurring near the end of the storm than peak rates from storms of uniform intensity or storms having their maximum intensity occurring early in the storm.
Abstract: Aprogrammable rainfall simulator was used to study the effects of variable intensity storm patterns on infiltration, runoff, and erosion When rain was applied to an initially dry soil, peak runoff rates were four to 20 times greater from storms having maximum intensities occurring near the end of the storm than peak rates from storms of uniform intensity or storms having their maximum intensities occurring early in the storm Soil loss from late peaking storms was two to eight times that from early peaking storms Runoff and soil loss from a storm of a given pattern occurring on a wet soil was greatest when preceding storms had maximum intensities occurring very early in the storm Apparent infiltration rate varied with rainfall intensity, which was likely caused by spatial variability of infiltration rates
78 citations
TL;DR: In this article, the authors used the arainfall simulator to determine runoff, infiltration, and soil loss from 1 m^ shrub and interspace plots on a sagebrush dominated site in southwestern Idaho.
Abstract: Arainfall simulator was used to determine runoff, infiltration, and soil loss from 1 m^ shrub and interspace plots on a sagebrush dominated site in southwestern Idaho. Interspace areas produced 2 1/2 times as much runoff and 8 times as much soil loss as from shrub canopy zones at this range site. High soil moisture conditions preceding rainfall simulation runs resulted in lower infiltration rates, increased runoff, and no significant difference in soil losses. Removal of shrub canopy did not significantly influence soil losses. Results of this study show the importance of understanding spatial variability in infiltration and the wide differences in potential erosion from shrub and interspace areas when predicting sagebrush rangeland erosion and applying erosion models on rangeland.
TL;DR: In this paper, a simulation study was conducted on three Minnesota soils to examine the effects of soil type, initial soil moisture content at the time of freezing, rate of freezing and number of freeze-thaw cycles, and energy of raindrop impact on aggregate stability.
Abstract: Arainfall simulator study was conducted on three Minnesota soils to examine the effects of soil type, initial soil moisture content at the time of freezing, rate of freezing, number of freeze-thaw cycles, and energy of raindrop impact on soil aggregate stability. For all three soils, the effect of raindrop impact energy was more pronounced than the effect of freezing and thawing on the disruption of soil aggregates. The rate of freezing had little or no significant effect on aggregate stability. While freezing, in general, resulted in a breakdown of soil aggregates, there were certain optimum soil moisture levels at which aggregate disruption as a result of frost action was minimized or reversed. The effect of number of freeze-thaw cycles on aggregate stability of the three soils tested was not consistent. Regression equations that relate the mean weight diameter of soil aggregates to these factors are presented.
TL;DR: In this paper, an electronic tree canopy volume measurement system was developed based on commercial ultrasonic range transducers with novel digital interface circuitry, which was mounted on an orchard air-blast sprayer for testing.
Abstract: AN electronic tree canopy volume measurement system was developed. The system was based on commercial ultrasonic range transducers with novel digital interface circuitry. The measurement system and a microcomputer were mounted on an orchard air-blast sprayer for testing. Calibration tests with ideal targets found system error to be
TL;DR: In this paper, the authors examined resuspending organisms from the stream bottom and found that cattle access to the stream increased organism concentration in the underlying sediments, while the exact fate of all of the organisms is not known.
Abstract: BACTERIA from livestock wastes enter streams with run-off and are deposited directly when animals have access to the stream. While the exact fate of all of the organisms is not known, some of the bacteria settle out into the sediment on the stream bottom. This study examined resuspending organisms from the stream bottom. Bear Creek flows through a semi-arid rangeland in Central Oregon. The stream bottom was disrupted (raked) at three locations along Bear Creek. The stream was monitored to determine the change in the concentration of fecal coliform (FC) and fecal streptococcus (FS). Cattle locations were also recorded throughout the study period. The rakings resuspended 1.8 million to 760 million FC per m^ and from 0.8 million to 5,610 million FS per m^. Cattle access to the stream increased organism concentration in the underlying sediments.
TL;DR: Alaser microreliefmeter was developed for field and laboratory measurements of surface roughness as discussed by the authors, which is a laser probe which is moved along a transect by a microprocessor-based motion control device.
Abstract: Alaser microreliefmeter was developed for field and laboratory measurements of surface roughness The microreliefmeter is a laser probe which is moved along a transect by a microprocessor-based motion control device The vertical surface coordinate is determined with the laser instrument with a maximum accuracy of 025 mm using the principle of triangulation The horizontal surface coordinates, representing the position of the laser probe on the transect and the transect position on the plot, are respectively determined by the motion control device with an accuracy of about 0001 mm or better and a metric tape measure with accuracy of about 05 mm Performance tests on soil surfaces yielded more consistent and reproducible values relative to those obtained by point gauge measurements Small errors in elevation measurements are made on surfaces with rapidly varying, non-uniform or discontinuous slopes The microreliefmeter is capable of measuring 26 m long transects, having different data point densities, and taking data at a rate of 27 observations/s It is not affected by differences in soil surface albedo or temperature
TL;DR: In this article, a mathematical model is presented that estimates variations in rill erosion parameters as a function of consolidation, defined as the increase in soil stability which occurs because of effective stresses in soils.
Abstract: SOIL erodibility changes with time after tillage. A mathematical model is presented that estimates variations in rill erosion parameters as a function of consolidation. Consolidation is defined as the increase in soil stability which occurs because of effective stresses in soils. Effective stresses are induced by negative soil water matric potentials that occur during moisture redistribution after rainfall. A method for calculating effective stresses is presented, as well as a relationship for relating effective stress history to changes in rill erosion resistance. An application of the model for field rill erosion of silt loam soil is presented.
TL;DR: In this article, the influence of simulated crop canopy cover, canopy height, and straw mulch cover on soil loss was studied in the laboratory and runoff was significantly reduced by increased Mulch cover but was unaffected by canopy cover or canopy height.
Abstract: THE influence of simulated crop canopy cover, canopy height, and straw mulch cover on soil loss was studied in the laboratory. Runoff was significantly reduced by increased mulch cover but was unaffected by canopy cover or canopy height. However, soil loss was significantly reduced by increased mulch cover and also by canopy cover when the cover was less than one meter above the soil surface. Mulch cover reduced soil loss for all particle classes. However, with increased mulch cover, the percentage of small aggregates and primary clay in the sediment increased while that of large aggregates decreased.
TL;DR: In this article, a model for estimating phosphorus loss from agricultural watersheds has been developed and incorporated into the ANSWERS watershed model, which uses ANSWER's extended sediment transport option to describe the transport of individual particle size classes.
Abstract: Asubmodel for estimating phosphorus loss from agricultural watersheds has been developed and incorporated into the ANSWERS watershed model. Model validation was accomplished using data from field plots. The model's usefulness as a planning tool was demonstrated on a watershed in Virginia. The model uses ANSWER'S extended sediment transport option to describe the transport of individual particle size classes. A nonequilibrium desorption equation is used to account for the desorption of phosphorus from the soil to surface runoff. Sediment-bound phosphorus is modeled as a function of the specific surface area of the soil and sediment. The equilibrium between soluble and sediment-bound phosphorus is modeled using a Langmuir isotherm.
TL;DR: In this paper, dry matter loss and change in quality were monitored from standing alfalfa through hay storage, and a wide swath into a windrow caused the greatest machine loss, which was inversely related to crop yield.
Abstract: DRY matter loss and change in quality were monitored from standing alfalfa through hay storage. Field curing loss consisted primarily of constituents other than fiber and protein and averaged 3.2% for hay dried without rain damage and 11.2% for hay with rain damage. Protein became less soluble during field curing and a small loss of protein occurred with rain damage. Raking a wide swath into a windrow caused the greatest machine loss; this loss was inversely related to crop yield. The portion of the yield lost was 3.5% for raking, 0.8% for windrow turning, 1.8% for the baler pickup and 1.1% from the baler chamber. Machine losses were similar across all quality constituents so the quality of harvested hay was not affected much by the loss. Storage loss of dry matter averaged 4.2% for dry hay (11 to 20% moisture), 7.9% for 20 to 25% moisture hay and 10.9% for hay of 25 to 34% moisture. This loss was predominantly constituents other than fiber (nonstructural carbohydrate and protein). Carbohydrate loss was proportional to the moisture content of the hay entering storage while protein loss appeared independent of hay moisture.
TL;DR: In this article, an automatic-iris lens and an optical filter were used to enhance image contrast to minimize computational image processing requirements, and a statistical-based algorithm was developed for selecting a threshold to segment row crop images into classes corresponding to the crop canopy and soil background.
Abstract: Astatistical-based algorithm was developed for selecting a threshold to segment row crop images into classes of information corresponding to the crop canopy and soil background. Systematic image sampling was used to determine an estimate of the population of pixels in an image. An automatic-iris lens and an optical filter were used to enhance image contrast to minimize computational image processing requirements. The threshold was selected using a Bayes classifier. The two image intensity classes were assumed to be independent Gaussian random variables. The distribution parameters used in classification were estimated using the method of moments. Data is presented on the development and performance of the thresholding algorithm on 16 representative row crop images. The algorithm was an effective classification technique for segmenting row crop images into crop canopy and soil background classes. In images with an extreme percentage of crop canopy or soil background, a priori knowledge of the class mixture was needed for convergence to the correct image thresholding parameters.
TL;DR: The Capillary Effect Root Environment System (CERES) uses capillary forces to maintain control of circulating plant nutrient solution in the weightless environment of an orbiting spacecraft.
Abstract: The construction of a permanently manned space station will provide the opportunity to grow plants for weeks or months in orbit for experiments or food production. With this opportunity comes the need for a method to provide plants with a continuous supply of water and nutrients in microgravity. The Capillary Effect Root Environment System (CERES) uses capillary forces to maintain control of circulating plant nutrient solution in the weightless environment of an orbiting spacecraft. The nutrient solution is maintained at a pressure slightly less than the ambient air pressure while it flows on one side of a porous membrane. The root, on the other side of the membrane, is surrounded by a thin film of nutrient solution where it contacts the moist surface of the membrane. The root is provided with water, nutrients and air simultaneously. Air bubbles in the nutrient solution are removed using a hydrophobic/hydrophilic membrane system. A model scaled to the size necessary for flight hardware to test CERES in the space shuttle was constructed.
TL;DR: The average particle number concentration from 75 samples of 1.76 to 7.01 jjim diameter particles was 11.2/mL as mentioned in this paper, which was significantly related to ventilation type, outside air temperature, inside/outside air temperature difference, and inside relativehumidity.
Abstract: THE total mass concentration of aerial dust particles in 11 swine finishing units averaged 8.1 mg/m^ during a 9-month survey and exceeded the 15 mg/m^ OSHA threshold in 13 of 88 farm visits. The average particle number concentration from 75 samples of 1.76 to 7.01 jjim diameter particles was 11.2/mL. Total particle mass and number concentrations were significantly related (P<.10) to ventilation type, outside air temperature, inside/outside air temperature difference, and inside relativehumidity. Inorganic contents of aerial and settled dust were 13.2 and 14.2%, respectively. Measures to remove aerial dust should emphasize proper management of ventilation equipment to assure reliable and sufficient airflow.
TL;DR: In this paper, an instrumented sphere that can sense and record such impacts was developed. Equations that use the recorded impact data to predict the size of bruise likely to be created on an apple were investigated.
Abstract: BRUISE damage usually results when an apple impacts either a hard surface or another fruit, and is a major cause of quality loss for fresh market apples. Research is underway to develop an instrumented sphere that can sense and record such impacts. Equations that use the recorded impact data to predict the size of bruise likely to be created on an apple were investigated. These predictions were compared to actual bruises on *Tda Red'' apples subjected to impact tests. A multiple linear regression model provided good predictions of bruise diameter.
TL;DR: In this paper, a subsurface drainage-runoff-erosion experimental area for the years 1981 to 1986 was used to measure the effect of surface drainage on soil, nitrogen, and phosphorus.
Abstract: SEDIMENT and nutrient losses were measured from a subsurface drainage-runoff-erosion experimental area for the years 1981 to 1986. The experimental area, located near Baton Rouge, LA, consisted of four surface drained plots, two of which were also subsurface drained. The plots were uniformly graded to a 0.1% slope and contained a clay loam alluvial soil. Subsurface drainage reduced surface runoff by 34%, soil loss by 30%, nitrogen loss by 20%, and phosphorus loss by 36%. Subsurface drainage increased total drainage by 35%.
TL;DR: In this paper, the application of computer vision as a sensing system for robotic harvesting of fruit was performed, where a vision system was developed to collect images and a computer algorithm was used to enhance and extract information from images.
Abstract: RESEARCH on the application of computer vision as a sensing system for robotic harvesting of fruit was performed. A vision system was developed to collect images. Testing was conducted during the day and at night on peach and apple trees. A computer algorithm was developed to enhance and extract information from images. This extracted information was used to classify objects within these images as either **multiple fruit, ^'single fruit, or '*noise. The algorithm correctly handled approximately 92% of the objects and identified approximately 89% of the fruit found in images obtained at night. Computer vision was determined to be a viable technique for detecting and identifying fruit on trees..
TL;DR: In this article, four common methods of deposition assessment, i.e., combinations of fluorometry and colorimetry on leaf and mylar targets were compared for use on citrus.
Abstract: USING Rhodamine-B and copper as tracers, four common methods of deposition assessment, i.e., combinations of fluorometry and colorimetry on leaf and mylar targets were compared for use on citrus. Merits and limitations of each method were identified. All were found to be reliable; however, considering limitations in the lab and in the field, colorimetric analysis of leaf samples appeared to be the most desirable method for deposition or residue assessment in citrus spraying.
TL;DR: In this paper, a computer vision system was used to evaluate external physical damage, mold contamination, and floury-to-vitreous endosperm ratio in corn and mold contamination in soybeans.
Abstract: Acomputer vision system was used to evaluate external physical damage, mold contamination, and floury-to-vitreous endosperm ratio in corn and mold contamination in soybeans. For each of these quality factors, optimal conditions for acquiring video images and processing algorithms were developed. White light in front-lighting mode with a black background for the sample was suitable for all defects except for mold contamination which required use of red light (610 nm). The image processing algorithms were suitable for defect detection in samples both individually and in groups. The average success rates for detecting broken, chipped, starch-cracked and moldy corn kernels were 100%, 83%, 88% and 84%, respectively. The success rate for detecting moldy soybeans was 80%.
TL;DR: In this paper, the effects of conventional tillage and no-till on the losses of runoff, sediment, and phosphorus (P) from agricultural lands were studied using an arainfall simulator, where a total of 100 mm of rainfall was applied to 12 0.01 ha plots, located on a silt loam soil.
Abstract: Arainfall simulator was used to study the effects of conventional tillage and no-till on the losses of runoff, sediment, and phosphorus (P) from agricultural lands. Three rye crop residue levels, 0, 750, and 1,500 kg/ha, were studied within each tillage system. Phosphorus fertilizer was applied at a rate of 46 kg/ha. A total of 100 mm of rainfall, with an intensity of 50 mm/h, was applied to 12 0.01 ha plots, located on a silt loam soil. Water samples were collected from H-flumes and later analyzed for sediment and P contents. No-till was found to be effective in reducing runoff and sediment losses. Runoff and sediment losses decreased as residue level increased, regardless of the tillage system. Increasing crop residue level from 0 to 750 kg/ha caused a decrease in average orthophosphorus (PO4) concentration for both tillage systems. However, as the crop residue level increased, from 750 to 1,500 kg/ha, the PO4 concentrations increased. Both PO4 and total-P (P4) losses were greatest with the 0 kg/ha residue treatment, intermediate with 1,500 kg/ha residue, and least with 750 kg/ha residue. The greater P losses from the 1,500 kg/ha, relative to the 750 kg/ha residue treatment, were attributed to higher P leaching from the crop residue of the 1,500 kg/ha treatment and insufficient suspended sediment to sorb P from solution for this level. No-till was very effective in reducing PO4, sediment-bound P (Psb), and Pj losses. Averaged over all residue levels, no-till reduced PO4, P^b, and Pj losses by 91, 93, and 97%, respectively, compared to conventional tillage.
TL;DR: In this paper, the authors proposed a surge irrigation technique to reduce the infiltration rate by consolidation of the furrow perimeter due to increased soil water tension during flow interruptions, filling of cracks with bed load during the following surge, and forced settlement of suspended sediment on the perimeter when the water supply is interrupted, and greater sediment detachment and movement caused by more rapid advance of the surged stream front.
Abstract: SURGE irrigation, the intermittent supply of water to furrows or borders, generally reduces infiltration rates. However, the degree of infiltration reduction is variable and difficult to predict. Mechanisms by which surge irrigation reduces infiltration rates include (a) consolidation of the furrow perimeter due to increased soil water tension during flow interruptions, (b) filling of cracks which develop during flow interruptions with bed load during the following surge, (c) forced settlement of suspended sediment on the furrow perimeter when the water supply is interrupted, and (d) greater sediment detachment and movement caused by more rapid advance of the surged stream front.
TL;DR: In this paper, an aerial photogrammetric method for making accurate and repetitive field measurements of ephemeral gully erosion is described. But, the development of appropriate predictive methodology along with the understanding of the erosional processes are limited by the difficulty of acquiring adequate data on ephemerale gully degradation.
Abstract: THE Universal Soil Loss Equation often under-estimates erosion on agricultural fields because it does not account for the loss of soil from ephemeral gullies. However, the development of appropriate predictive methodology along with the understanding of the erosional processes are limited by the difficulty of acquiring adequate data on ephemeral gully erosion. This paper describes an aerial photogrammetric method for making accurate and repetitive field measurements of ephemeral gully erosion. Stereo aerial photographs are aquired of a field before and after gully changes caused by erosion or tillage. Data reduction of the stereopairs with photogrammetric procedures provides X, Y and Z terrain coordinates with approximate vertical measurement accuracies of ± 25 mm and contour intervals of 0.15 m. The methodology was tested on a 5.34 ha field that contained two major gullies with eroded depths approaching 0.5 m. Over nearly three years, soil volume changes in the gullies were computed to give the quantities of soil removed by erosion or filled by tillage. The distribution of the soil volume changes along the gullies portrayed the zones and quantities of deposition as well as erosion. This data base offers considerable potential for studying ephemeral gully erosion and developing predictive methodology.