Showing papers in "Transactions of the ASABE in 1990"
TL;DR: In this article, empirical equations that relate soil penetration resistances from a 5-mm diameter, flat-tipped probe to soil water content were evaluated and several relationships were developed statistically for United States Southeastern Coastal Plain Ultisols from Norfolk loamy sand data and verified by other data of that soil and other soils.
Abstract: Soil penetration resistance readings that need to be compared are often taken at different soil water contents. Because soil water can significantly effect penetration resistance, it is often difficult to determine whether penetration resistance differences are caused by water content or treatment. Empirical equations that relate soil penetration resistances from a 5-mm diameter, flat-tipped probe to soil water content were evaluated. The purpose of these equations was to adjust soil penetration resistance with changers in soil water content from plot to plot or time to time in the same plot. Several relationships were developed statistically for United States Southeastern Coastal Plain Ultisols from Norfolk loamy sand data and verified by other data of that soil and other soils. Penetration resistance (PR) was related to water content (WC) and bulk density for laboratory samples with R^ ranging from 0.86 to 0.96. When the ratio of functions of water contents was related to the ratio of the penetration resistances, in most cases bulk density cancelled out and R^ ranged from 0.44 to 0.99. The R^ for the field samples ranged from 0.78 to 0.90, with one value at 0.25 for the relationship between penetration resistance and water content and bulk density, and 0.53 to 0.80 for the ratios. Some of the best relationships were developed from equations that considered boundary conditions of PR = 0 for WC = saturation and PR = «. for WC = 0. These fit the data as well as or better than more empirical relationships but used fewer parameters.
262 citations
TL;DR: Sensitivity analysis of a physically based simulation model is used for assessing the rationality of the model, to provide insight into the overall physical system which the simulation model represents, and to help identify research needs as mentioned in this paper.
Abstract: Sensitivity analysis was performed on the hillslope profile erosion model developed by the USDA-Water Erosion Prediction Project. The erosion model calculates soil loss and sediment yield caused by rill and interrill erosion on complex shaped hillslope profiles. Sensitivity analysis of a physically based simulation model is used for assessing the rationality of the model, to provide insight into the overall physical system which the simulation model represents, and to help identify research needs. Changes in predicted soil erosion and sediment yield as a function of changes in soil, plant residue and canopy, hillslope topography, and hydrologic input variables were assessed. Dominant factors related to model response were precipitation, rill erodibility, rill residue cover, and rill hydraulic friction factors. Saturated hydraulic conductivity and interrill erodibility were moderately sensitive parameters. Other factors which had less influence on output were canopy height, interrill cover, soil bulk density, antecedent moisture, peak rainfall intensity, time to pe^ rainfall intensity, rill width and spacing, and sediment characteristics. Slope length, gradient, and slope shape effects on soil loss and sediment delivery were also discussed.
215 citations
TL;DR: In this paper, a linear transformation of the normalized difference (ND) was used as the reflectance-based crop coefficient (Kcr), which equates the ND for dry bare soil and the ND at effective cover, to the basal crop coefficient for dry soil evaporation and at effective covering, respectively.
Abstract: Concurrent measurements of reflected canopy radia-tion and the basal crop coefficient (K^b) for corn were conducted throughout a season in order to develop a reflectance-based crop coefficient model. Reflectance was measured in Landsat Thematic Mapper bands TM3 (0.63 - 0.69 um) and TM4 (0.76 - 0.90 um) and used in the calculation of a vegetation index called the normalized difference (ND). A linear transformation of the ND was used as the reflectance-based crop coefficient (Kcr). The transformation equates the ND for dry bare soil and the ND at effective cover, to the basal crop coefficient for dry soil evaporation and at effective cover, respectively. Basal crop coefficient values for com were obtained from daily evapotranspiration measurements of corn and alfalfa, using hydraulic weighing lysimeters. The Richards growth curve function was fitted to both sets of data. The K^b values were determined to be within -2.6% and 4.7% of the K^^ values. The date of effective cover obtained from the K^b data was within four days of the date on which the ND curve reached its maxima according to the Richards function. A comparison of the Kcr with basal crop curves from the literature for several years of data indicated good agreement. Reflectance-based crop coefficients are sensitive to periods of slow and fast growth induced by weather conditions, resulting in a real time coefficient, independent from the traditional time base parameters based on the day of planting and effective cover.
199 citations
TL;DR: In this paper, a submerged, vertical jet device was designed to measure in situ soil erodibility, and a linear model was used to determine the best fit relationship of these variables.
Abstract: A submerged, vertical jet device was designed to measure in situ soil erodibility. Performance of the vertical jet device was calibrated based on comparisons of erodibility of three soils determined from large scale open channel testing. The results indicate that the scour factor can be related to the Reynolds number of the jet, the time factor, and the erodibility factor by a linear relationship in logarithmic scale. A linear model was therefore used to determine the best fit relationship of these variables. This equation was used to determine the coefficient of erodibility, K, from the jet test results of a soil.
181 citations
TL;DR: In this paper, the authors determined rill density and rill flow rates during rainfall simulation tests conducted at 11 sites located throughout the eastern United States and found that rill densities of 1.0 rills/m were found for the study locations.
Abstract: Rill density and rill flow rates were determined during rainfall simulation tests conducted at 11 sites located throughout the eastern United States. A mean rill density of 1.0 rills/m was found for the study locations. From measurements of the relative distribution of flow rates, a procedure is identified for partitioning flow between individual rills. Regression equations were developed for relating rill width and hydraulic roughness coefficients to flow rate. Equations were also derived for predicting mean flow velocity from visually determined measurements of advance velocity. Information reported in this study can be used to estimate hydraulic characteristics of rills.
162 citations
TL;DR: In this article, a method of identifying plants based on color texture characterization of canopy sections was developed, where color co-occurrence matrices were derived from image matrices, one for each color attribute: intensity, saturation, and hue.
Abstract: A method of identifying plants based on color texture characterization of canopy sections was developed. Color co-occurrence matrices were derived from image matrices, one for each color attribute: intensity, saturation, and hue. Eleven texture features were calculated from each of the co-occurrence matrices. The 33 total color texture features were used in a discriminant analysis model to identify plants. Overall classification accuracy of 91% was achieved when this method was used to identify seven common cultivars of nursery stock. A total of 350 observations were used in the investigation. This method exhibited a significant improvement over previous methods which used intensity data only.
138 citations
TL;DR: In this article, the authors defined atmospheric ammonia concentrations from poultry litter as a function of environmental variables such as air temperature and relative humidity in a common room and air flow and moisture content in each chamber.
Abstract: Volatilization of ammonia from poultry litter in broiler houses creates potential health hazards for the house operator and the birds. This problem was addressed by defining atmospheric ammonia concentrations from broiler litter as a function of environmental variables. Nine chambers, each 1.37 m^ in volume, were constructed and positioned in a common room. Air temperature and relative humidity in the common room were controllable. Air flow (i.e., ventilation) rates through each chamber and the litter moisture content in each chamber were also controllable. An attempt to control litter pH was not successful. Using a second-order central composite rotatable statistical design, data were collected from the small chambers that allowed both litter pH and ammonia volatilization rate to be expressed as a function of litter moisture content, ventilation rate, and air relative humidity and temperature. Response surfaces developed from this data are presented.
123 citations
TL;DR: In this paper, the authors measured interrill erodibility on eighteen cropland soils in the western half of the United States, using a rotating boom rainfall simulator, and proposed a slope factor, based on plot slope, to account for differences observed in interrill erosion rates.
Abstract: Interrill erodibility was measured on eighteen cropland soils in the western half of the United States, using a rotating boom rainfall simulator. There were significant differences in infiltration rates, runoff rates, and erosion rates among the soils. A slope factor, based on plot slope, to account for differences observed in interrill erosion rates, is proposed. The data show that this slope factor may also be a function of soil properties. An interrill erodibility coefficient is proposed for each soil.
101 citations
TL;DR: In this paper, a machine vision algorithm for grading fresh market produce according to color and damage was developed, treating the relative hue distribution of pixels in six orthogonal views as quantitative variables, discriminant analysis was used to classify observations.
Abstract: A machine vision algorithm for grading of fresh market produce according to color and damage was developed. Red-green-blue pixel intensity values were mapped to one of eight possible hues. Treating the relative hue distribution of pixels in six orthogonal views as quantitative variables, discriminant analysis was used to classify observations. When applied to the task of grading bell peppers, accuracies of up to 96% and 63% were found for grading by color and damage, respectively..
85 citations
TL;DR: In this paper, a computer model is proposed to predict the effects of animal waste management practices on the bacteria concentration of runoff from agricultural lands using Monte Carlo simulation to combine the deterministic relationships with statistical knowledge concerning rainfall and temperature variation.
Abstract: Runoff from agricultural lands carrying microorganisms from livestock manure can contaminate the food and water supplies of both animals and humans. Planning and design of animal waste management practices, thus, becomes more important as livestock populations become more concentrated. A computer model is proposed to predict the effects of animal waste management practices on the bacteria concentration of runoff from agricultural lands. The model uses Monte Carlo simulation to combine the deterministic relationships with statistical knowledge concerning rainfall and temperature variation. The model outputs maximum and minimum bacteria concentrations in runoff resulting from a storm assumed to occur immediately after manure is applied to the land. The model can simulate the effects of waste storage, filter strips, and incorporation of manure into the soil. Data and information collected from the Owl Run watershed in Fauquier County, Virginia is used to demonstrate the model's applicability and potential. Long-term manure storage was found to be the most appropriate practice for reducing bacteria concentrations for the study site. Incorporation of manure was as effective as long-term storage, but is more costly. Buffer strips alone were not sufficient for reducing bacteria concentrations to meet the water quality goal. Since animal waste management practices have only recently been implemented on the watershed, no field data is yet available to validate the model's predictions.
84 citations
TL;DR: In this paper, the authors conducted open channel testing of soil erodibility on four soils and found that the soil texture and plasticity were related to the observed erodibilities.
Abstract: Open channel testing of soil erodibility was conducted on four soils. Large scale channels were constructed outdoors with the soil material placed throughout the entire length of the channel beds. Changes in channel bed roughness were observed and incorporated into the analysis. The relative surface erodibilities of the four soils are reported. Soil texture and plasticity are shown to be related to the observed erodibilities.
TL;DR: In this paper, a relationship is derived that describes the variation of the horizontal component of mass flux, fx, downwind of a distinct field boundary, and the derived functional relationship is then verified and completed through the use of field data.
Abstract: Elementary analysis of the wind erosion process within a flat and uniform field is presented. A relationship is derived that describes the variation of the horizontal component of mass flux, fx, downwind of a distinct field boundary. The derived functional relationship is then verified and completed through the use of field data. The generalized form of the equation contains two parameters, fj^j^ and b, that describe different aspects of the wind erosion process. The quantity f^^^ is the maximum horizontal flux for a given height. The length scale b represents the distance at which f,^ attains a value of 63.2% of f^x-
TL;DR: In this paper, the effects of rice herbicide formulations, concentrations, and tank mixtures; surfactants; polymers; and spray nozzle orientation in an airstream were determined in relation to the size of spray droplets produced by hollow cone nozzles.
Abstract: spray droplet size is a major concern to herbicide applicators because: 1) most post-emergence herbicides must be applied uniformly and give complete coverage of target plants for greatest efficacy; and 2) spray drift to non-target areas must be minimized. The effects of rice herbicide formulations, concentrations, and tank mixtures; surfactants; polymers; and spray nozzle orientation in an airstream was determined in relation to the size of spray droplets produced by hollow cone nozzles. Several droplet-size statistics were significantly affected by herbicide formulations, tank mixtures, and polymer concentrations. Increasing the concentration of herbicide in the spray mixture or changing the nozzle orientation from 0 to 45° with respect to the airstream affected droplet size less than mixture type or polymer concentration.
TL;DR: In this article, an algorithm was developed to shift the basal crop coefficient (K^b) curve with respect to its time axis to obtain a K^b in accordance with the real time reflectance-based crop coefficient for corn.
Abstract: An algorithm was developed to shift the basal crop coefficient (K^b) curve with respect to its time axis to obtain a K^b in accordance with the real time reflectance-based crop coefficient for corn. Adjustment of the emergence and effective cover dates during vegetative growth made these dates converge on their actual occurrence. Impact of adjustments to the K^b curve on irrigation dates was simulated using the USDA-ARS irrigation scheduling model for two seasons. Simulated results for the 1983 growing season showed one or two-day differences in the occurrence of irrigation dates. Prior to effective cover, irrigations occurred earlier for the simulation using feedback (adjusted K^b). After effective cover, irrigation dates lagged for the with-feedback simulation compared to the without-feedback simulation. An extra irrigation was required prior to effective cover in 1983 for the simulation using feedback. In 1986, one less irrigation was required for the simulation using feedback to the irrigation scheduling model. This was due to K^b curve adjustments that accounted for hail damage and ensuing cool weather that slowed plant growth during early vegetative growth. The first two irrigations were delayed by two and three days, respectively, due to these events for the with-feedback simulation when compared to simulated results obtained not using feedback. Results from the simulation indicated the following: 1) revised or adjusted K^b curves derived from spectral inputs are unique to the individual growing season, 2) conventional crop coefficients contribute to underestimation as well as overestimation of crop ET because they cannot account for variable crop growth rates, and 3) adjusting the K^b curve in response to actual crop growth allows proper timing of irrigations to ensure that soil moisture conditions are ideal throughout the growing season.
TL;DR: In this paper, an elastic sphere model was developed that utilized an observed resonant frequency to predict the modulus of elasticity of the apple, and the predictions were compared with measured values of Magness-Taylor firmness and modulus for elasticity.
Abstract: Apple modulus of elasticity was readily predicted (r^ > 0.76) from acoustic resonant frequency vibrations caused by an impulse striking the apple. Magness-Taylor fiminess was poorly predicted (r^ < 0.27) using the same technique. An elastic sphere model was developed that utilized an observed resonant frequency to predict the modulus of elasticity of the apple. These predictions were compared with measured values of Magness-Taylor firmness and modulus of elasticity..
TL;DR: In this article, the authors developed a wind simulator to furnish wind direction and sub-hourly wind speed to users of wind speed information, particularly for wind erosion modeling, which is useful to those needing wind speed and wind direction information and provide the wind simulator requirements in a wind erosion prediction system.
Abstract: The purpose of this study was to develop a wind simulator to furnish wind direction and sub-hourly wind speed to users of wind speed information, particularly for wind erosion modeling. We analyzed the Wind Energy Resource Information System data to determine scale and shape parameters of the WeibuU distribution for each of the 16 cardinal directions for each month at 704 locations in the United States. We also summarized wind direction distributions, ratio of daily maximum to daily minimum wind speed, and hour of maximum wind speed by month for each location. This summary of historical wind statistics constitutes a compact data base for wind simulation. Equations were formulated and procedures developed and used with the compact data base and a random number generator to simulate wind direction and sub-hourly wind speed. Cumulative wind speed distributions, calculated from the WeibuU parameters, and wind speeds simulated at one-hour intervals for 1000 days agreed well. The model reflects historical day-to-day wind variation and wind speed variations within a day. It will be useful to those needing wind speed and wind direction information and will provide the wind simulator requirements in a wind erosion prediction system.
TL;DR: In this article, the evapotranspiration research lysimeters with 1 nfi area and 1.2 m depth were designed and constructed using commercially available cantilever load cells and operated continuously for a three-year period at the Drainage Research Farm of Utah State University.
Abstract: Evapotranspiration research lysimeters with 1 nfi area and 1.2 m depth were designed and constructed using commercially available cantilever load cells. These lysimeters were operated continuously for a three-year period at the Drainage Research Farm of Utah State University. Resolution of daily measurements of evapotranspiration (Et) from the fescue/forage grass mix was generally better than 0.05 mm or 1%. Accuracy of hourly measurements of E^ was influenced by numerical resolution of the data logger and slight thermal instabilities within the load cells. Lysimeter measurements agreed well with Et estimated with the Penman-Monteith method. The total cost for a two-lysimeter installation including labor was $11,000. Maintenance and operation requirements were low.
TL;DR: In this paper, a hydrograph separation technique, using a mass balance and the assumption of a dual porosity model, was applied to tracer concentrations and flow rate of drainage water to estimate the preferential and matrix flow components of subsurface drainage.
Abstract: Potassium bromide and calcium nitrate were used as tracers in sprinkler irrigation water and applied to a field plot drained with a single subsurface drain line during two irrigations. Irrigations were centered above a drain conduit installed 1.1m below the soil surface. Drain flow was measured, and water samples were collected from drain discharge and analyzed for NO3 and Br content. A hydrograph separation technique, using a mass balance and the assumption of a dual porosity model, was applied to tracer concentrations and flow rate of drainage water to estimate the preferential flow and matrix flow components of subsurface drainage. Individual hydrographs of both matrix and preferential flow were constructed. Preferential flow was found to contribute less than 2% of the total drain outflow but, nonetheless, transported on a mass basis: 24% and 12% of the bromide and 20% and 9% of the nitrate reaching the drain, respectively, during two sprinkler irrigations.
TL;DR: Alfalfa was ensiled at different dry matter (DM) levels as discussed by the authors, and the results suggest variations in the dominant lactic acid bacterial strains as a function of DM content.
Abstract: Alfalfa was ensiled at different dry matter (DM) levels. Increasing DM content reduced the rate and total amount of fermentation and resulted in a higher pH. The ratio of fermentation end products varied with both DM content and time. The highest relative levels of lactic acid were in silages of 40 to 55% DM. Acetic and succinic acids were highest in unwilted silages, and relative production of ethanol was greatest in > 60% DM silages. These results suggest variations in the dominant lactic acid bacterial strains as a function of DM content. High amounts of startch hydrolysis observed in unwilted alfalfa were the result of high starch contents in the crop at the ensiling. Glucose addition reduced final pH only in silages of less than 50% DM where substrate level limited fermentation.
TL;DR: In this paper, a mobile grove-lab was developed to study the use of robotic technology for picking oranges under actual production conditions, and the design and operation of the citms picking robot developed for this facility is described.
Abstract: A mobile grove-lab was developed to study the use of robotic technology for picking oranges under actual production conditions. The design and operation of the citms picking robot developed for this facility is described. The sensor system developed to identify and locate fruit in real-time and the state network programming technique used to develop a task-level control program for the citrus picking robot are discussed. The suitability of the vision system and state network programming technique for real-time, vision-servo robotic picking is demonstrated. It was concluded that the technical and economic practicality of robotic citrus harvesting can only be demonstrated with an operational multiple-arm harvesting system. Multiple usage of robotic harvesting equipment and acquisition of detailed production data by a robotic harvester were identified as intangible benefits of robotic harvesting which should encourage the commercial development of a multiple-arm machine.
TL;DR: In this paper, the authors derived the relaxation modulus, ultimate compressive and tensile strength of soybean cotyledon using stress relaxation, compression, and bending tests.
Abstract: The relaxation modulus, ultimate compressive and tensile strength of soybean cotyledon were determined using stress relaxation, compression, and bending tests. The master curve for the cotyledon relaxation modulus was derived using the time-moisture and time-temperature shifting technique. Both the relaxation modulus and the ultimate strength were lower at higher moisture contents during drying at higher temperatures. A two-term Maxwell model was derived to describe the behavior of the soybean cotyledon. The soybean cotyledon can be treated as a thermo-hydro-rheologically simple viscoelastic material.
TL;DR: In this paper, the feasibility of determining strength and other related soil physical properties as they change over winter was examined by using Torvane shear devices, a pocket penetrometer, and a modified Swedish fall-cone device.
Abstract: This study, conducted over the winters of 1987/88 and 1988/89, examined the feasibility of determining strength and other related soil physical properties as they change over winter. Soil strength was measured with two Torvane shear devices, a pocket penetrometer, and a modified Swedish fall-cone device. Soil water content was determined gravimetrically. Frost depth was determined with a CRREL-Gandahl type frost gage and also by probing the soil with a knife. Strength was measured best, under the conditions encountered, with a metal Torvane device. Strength ranged from 1.2 kPa during soil thawing to 14 kPa under dry soil conditions. Under sunny and windy conditions, thaw-weakened soil regained most of its strength within a few hours after thaw. Strength was found to be inversely related to the water content of the top 10 mm of the soil profile. The soil water content of this layer during or immediately after rain or snow melt on unfrozen soil did not exceed 25% by weight; whereas, soil water content was as much as 58% while the soil was frozen and 44% while the soil was thawing.
TL;DR: In this paper, a three-dimensional heat conduction problem in cartesian coordinate system was solved using the finite element method for predicting the temperature distribution in grain storage bins, which can handle linear and quadratic hexahedron elements with 1, 2, or 3 point Gauss quadrature in each plane.
Abstract: A three-dimensional, heat conduction problem in cartesian coordinate system was solved using the finite element method for predicting the temperature distribution in grain storage bins. The program can handle linear and quadratic hexahedron elements with 1, 2, or 3 point Gauss quadrature in each plane. The model can simulate the temperatures in filled grain bins of any shape and at any location, if the hourly weather data (solar radiation, wind velocity, and ambient air temperature) for the location and the grain temperatures at the start of simulation are available. Other input data required for the model include the three dimensional grid data of a linear or quadratic hexahedron element, and the thermal properties of grain, bin wall material, soil and air. Temperatures predicted by the model were in very good agreement with the measured temperatures in two 5.56 m diameter bins containing rapeseed and barley, respectively, located near Winnipeg. Temperatures predicted by the model in 3.0 m and 4.0 m tall rapeseed bulks of various diameters were compared with the temperatures predicted by 2D finite difference and 3D finite difference models. The temperatures predicted by the 3D finite element model and the 3D finite difference model were nearly identical for different locations in the grain bulks. Three dimensional finite element model predicted higher temperatures by about 5 K to 15 K towards the south side of the bin than the north side, whereas 2D model predicted equal temperatures at these locations.
TL;DR: In this article, simulations of soybean and com (maize) growth for the southeastern U.S.A. were run for 30 baseline years of weather data, 1951-80, for 19 locations with and without supplemental irrigation, using SOYGRO and CERES-Maize crop models.
Abstract: Simulations of soybean and com (maize) growth for the southeastern U.S.A. were run for 30 baseline years of weather data, 1951-80, for 19 locations with and without supplemental irrigation, using SOYGRO and CERES-Maize crop models. Runs were also made for climatic changes predicted by two General Circulation Models (GCMs) for a doubling of atmospheric carbon dioxide. One climate change scenario resulted in over 50% reduction in rainfed seed yields for both crops, while the impact of the second scenario was negligible. Under irrigation, the simulated results indicated doubled CO2 produced 20% less corn and 14% more soybean, somewhat independent of the climate change scenario. Irrigation water demand was significantly increased.
TL;DR: A finite element program has been developed that used a compaction model for agricultural soils developed at the National Soil Dynamics Laboratory (NSDL) and Auburn University to predict linear elastic parameters for each element in the model.
Abstract: A finite element program has been developed that used a compaction model for agricultural soils developed at the National Soil Dynamics Laboratory (NSDL) and Auburn University to predict linear elastic parameters for each element in the model. Incremental loading was used by the finite element model to gradually load the soil so that these linear parameters could be varied many times over the loading period. The finite element model was compared with data obtained from soil bin research. Results showed that a flat disc load was modeled well but a spherical disc load was not.
TL;DR: In this paper, an 89mm diameter self-contained, instrumented sphere (IS) was developed to record impacts it experiences while handled with like-sized commodities (apples, pears, peaches, oranges).
Abstract: The transportation and handling of agricultural products can result in various degrees of damage due to impacts. An 89-mm diameter self-contained, instrumented sphere (IS) was developed to record impacts it experiences while handled with like-sized commodities (apples, pears, peaches, oranges). This unit is approximately 1/4 the diameter of an earlier reported system, and has 32K of memory, EEPROM, smaller batteries, and simplified conditioning circuitry. The populated circuit board is foam insulated and then cast in beeswax for structural hardness. Analysis of recorded accelerations above a preprogranmied threshold allows estimates of fruit bruising that results from various impacts. Extensive laboratory drop tests were done using fruit and the IS to evaluate the reliability of predicted damage based on various impact characteristics (peak acceleration, velocity change).
TL;DR: In this paper, a two-year study was conducted to determine how crop growth and grain yield were affected by excess soil water, and the results indicated a linear decrease in the relative yield with increasing wetness (SDI values), but the best-fit regression lines of the yield-SDI data for the undrained area differed considerably between years.
Abstract: In a two-year study, com was subjected to controlled flooding during various physiological stages of growth by using specially constructed isolated field plots to determine how growth and grain yield were affected by excess soil water. Com was most susceptible to flooding at the early-vegetative stage (36 days after planting) with maximum reductions in plant-canopy height, dry-matter production, and grain yield. Two-year averages of the crop susceptibility (CS) factors calculated from the yield data were 0.64, 0.44, 0.15, and 0.19 for early-vegetative, late-vegetative, flowering, and yield-formation stages of growth, respectively. The SDI concept was tested by comparing the relative yield-SDI relationships for a nearby area with naturally fluctuating water tables using CS values obtained in this study. The SDI models indicated a linear decrease in the relative yield with increasing wetness (SDI values), but the best-fit regression lines of the yield-SDI data for the undrained area differed considerably between years.
TL;DR: In this article, a finite element formulation and solution of a set of coupled conductive heat and diffusive moisture transfer equations to improve grain drying simulation of axisymmetric bodies is presented.
Abstract: A finite element formulation and solution of a set of coupled conductive heat and diffusive moisture transfer equations to improve grain drying simulation of axisymmetric bodies is presented. The model considers the temperature and moisture dependence of the diffusion coefficient, thermal conductivity, and specific heat. It assumes that moisture diffuses to the outer boundaries of the kernel in liquid form and that evaporation takes place only at the surface of grain. Application was made to drying of a barley kernel and predicted results agreed well with the experimental data. The simulated temperature and moisture profiles and gradients are directly usable for stress cracking analyses of grain. The results of the finite element analysis can be used for grain quality evaluation and drying simulation studies.
TL;DR: In this article, three different climate change scenarios, with and without supplemental irrigation, were used with the SOYGRO crop model to simulate soybean growth and yield for 19 locations in southeastern U.S.A. were simulated for 30 years (1951-80) of climate data.
Abstract: Soybean growth and yield for 19 locations in southeastern U.S.A. were simulated for 30 years (1951-80) of climate data. Three different climate change scenarios, with and without supplemental irrigation, were used with the SOYGRO crop model. The three climate scenarios were standard historic data and two scenarios based on changes predicted by two general circulation models (GCM) for a doubling of atmospheric carbon dioxide. Results were analyzed for four different conditions; normal weather, doubled CO2 alone, climate change alone, and the combined effect of climate change and doubled CO2. Results indicate 1) yields vary widely with climate scenario; 2) increased water use and irrigation need for the combined case of doubled CO2 and climate change; and 3) simulation is a useful tool for this type of study.