Showing papers in "Transactions of the ASABE in 1983"

Modeling Soybean Growth for Crop Management

Abstract: Asoybean (Glycine max (L.) Merr.) crop growth simulation model (SOYGRO) was developed to aid farm managers in making irrigation and pest management decisions. Non-linear first order differential equations describe dry matter rates of change, accumulation and depletion of protein pools, and changes in shell and seed numbers. Two data sets from defoliation and irrigation experiments were used for calibration and validation of the model. The model responds well to drought and defoliation stresses for two test cases. Sensitivity analyses of SOYGRO revealed that simulated yield was most sensitive to changes in gross photosynthesis and growth respiration. The sensitivity of simulated yield to changes in model parameters was increased by the occurrence of either water or defoliation stress.

Estimation of Erosion Index from Daily Rainfall Amount

Abstract: A method was developed for estimating the erosion in-dex for rainfall events from daily rainfall amount. The relationship that was used includes both a deter-ministic component and a random component. Data from 22 locations in the eastern one-half of the United States were used to evaluate the relationship. The parameters of the relationship were found to vary both with location and with season at a location. The pro-cedure was used to estimate erosion index from daily rainfall data for two locations.

Agricultural Management Effects on Soil Water Processes Part I: Soil Water Retention and Green and Ampt Infiltration Parameters

Abstract: A method for predicting changes in soil porosity caused by different types of tillage is developed. Soil porosity change is incorporated into procedures for estimating soil water retention properties and Green and Ampt parameters based on soil texture, or soil separates, organic matter, and bulk density.

Bacterial Pollution from Agricultural Sources: A Review

Abstract: T potential for environmental contamination through the indiscriminate handling of agricultural wastes has been a topic of intensive research during the past two decades. The potential for disease transmission is the major bacteriological problem where public health is concerned. Bacterial pollution of the soil through land application of manures and sludges can also affect the indigenous soil populations and change the decomposition and nutrient recycling rates (Doran, 1979). More than twenty diseases have been identified as possibly transferred from animal manures (Azevedo and Stout, 1974). Several reviews have been written dealing with the health aspects of waste application (Sagik and Sorber, 1978; Menzies, 1977; Burge and Marsh, 1978; Diesch, 1970; Weaver et al., 1978; Dunlop, 1976; Strauch, 1976; Rankin and Taylor, 1969). Land application of wastes may spread disease via several pathways. Few disease outbreaks have been caused by bacteria of livestock origin but this possibility was shown by Jack and Hepper (1969) where salmonellosis mortality was traced to seepage from a slurry tank overflow. Rankin and Taylor (1969), studying dairy manure slurry, found several different species of bacterial pathogens in samples from various farms. Beef feedlot runoff has been shown to contain Salmonella infantis in an investigation by Miner et al. (1967). Historically, bacterial indicators have been used to monitor the pollution of surface and ground waters from domestic and animal sources. Total coliforms are used to monitor treated water to determine post treatment contamination. In systems involving pollution from land areas and runoff, many coliform sp. of natural origin (non-enteric) can be introduced so as to make this organism ineffective as a true sign of fecal contamination. Fecal coliforms eliminate this problem because they are only produced in the intestines of warm blooded animals. Fecal streptococci are less specific in nature but are also predominately isolated only from enteric sources (Geldreich, 1976). Problems in identification and specificity of testing methods for elimination of non-enteric fecal streptococci sp. is native to vegetation, soil and insects have been reported (Kibbey et al., 1978; Hunt et al., 1979; Geldreich, 1976). The "best" choice of indicator for any particular study depends on the sample source, environmental conditions and geographic location as well as the use to be made of

Soybean Oil Fuel in a Small Diesel Engine

Abstract: SHORT term performance tests were conducted to evaluate crude soybean oil, crude-degummed soybean oil and soybean ethyl ester as complete substitutes for No. 2 diesel fuel in a small diesel engine. A longer term evaluation of the engine when using 100% crude soybean oil was prematurely terminated. Severe injector coking led to decreases in power output and thermal efficiency

lepa irrigation system evaluation

Abstract: THE LEPA (Low Energy Precision Application) irrigation concept has been extensively tested for two years and compared with sprinkler and furrow methods. The evaluation included application efficiency, distribution efficiency, water use efficiency and energy savings potential. The LEPA system was superior in all categories. Soybeans were used as a test crop and the yield data support the irrigation efficiency results and indicate an economic justification for conversions to LEPA irrigation.

field quantification of crop water stress

Abstract: CANOPY temperature is used to quantify crop stress by use of a crop water stress index (CWSI). The index can be developed empirically and theoretically and advantages of each approach are described. Relationships between the CWSI and traditional plant stress parameters such as leaf water potential and stomatal conductance are presented for cotton. The daily change in CWSI for cotton shows its dynamic response to changing atmospheric demand and soil moisture conditions. The value of the CWSI is shown in terms of scheduling irrigations and predicting lint cotton yield.

Agricultural Management Effects on Soil Water Processes Part II: Green and Ampt Parameters for Crusting Soils

Abstract: THE Green and Ampt infiltration equation is adapted to agricultural soils subject to soil crusting. Procedures are presented for predicting crusting soil parameters from the factors of soil texture, soil surface cover, and surface roughness. The potential magnitude of crusting effects on infiltration rates is presented.

Time-Dependent Aspects of the Strength and Rheology of Vegetative Tissue

Abstract: THIS paper presents a mathematical model for the cellular structure of vegetative tissue, taking into account the viscoelastic properties of the individual cells. The model is used to develop qualitative predictions for the effect of cell turgidity and rate of loading on tissue stiffness, stress at failure, and strain at failure. For a single cell, the model indicates that yielding can occur due either to cell wall failure or cell relaxation from the migration of cell fluids out of the cell. A review of previous experiments and new data presented in this paper indicate that the model gives a good representation of the time-dependent behavior of apple tissue in compression. Strain at failure is significantly lower at high strain rates and/or with more turgid samples. Stress at failure may or may not be affected by turgidity and rate of loading. Tissue stiffness is increased by increased cell turgidity and rate of loading.

Drip Irrigation Field Uniformity Estimation

Abstract: THE coefficient of variation was used to assess the magnitude of emitter flow variation in drip irrigation submain units. Based upon the assumption that emitter flow variation is normally distributed, a simplified statistical method for estimating the coefficient of variation was developed. The estimate of the coefficient of variation was used to demonstrate a method of determining field uniformity for drip irrigation submain units. A graphical technique for estimating the statistical uniformity and the relative confidence limits of the proposed method were presented.

Spray Losses and Partitioning of Water Under a Center Pivot Sprinkler System

Abstract: CENTER pivot irrigation is extensive in the Great Plains agricultural region. The efficiency of a center pivot sprinkler system was analyzed by monitoring spray losses under various climatic conditions and by examining the partitioning of water within a corn (Zea mays L.) canopy. Average spray losses were 12% in 1980 and 16% in 1981. Spray losses were significantly correlated with vapor pressure deficit (r^ = 0.49), temperature (r,^ = 0.47) and a wind-vapor pressure deficit term (rXjy = 0.45). The unexplained variability in the data may be attributed to the difficulty of determining the exact application rate at a particular area of the field and to the interaction between climatic conditions and wind orientation relative to the sprinkler lateral. Under full canopy condition in corn, about half of the water reaching the soil surface is via stemflow with the remainder falling or dripping through to the soil surface. We found 2.7 mm of canopy storage in a full corn canopy. Net loss of plant intercepted water depends on the temperature and on the ratio of canopy (rc) and aerodynamic (ra) resistances to vapor flux, with net losses being small if rc/ra is low and temperatures are high.

Effect of Plant Roots and Root Channels on Solute Transport

Abstract: SINCE many of the practical applications of solute modeling are to situations where crop roots are present, it is necessary to investigate the effect of roots and void root channels on the transport of solutes through soils. In an attempt to do this chloride breakthrough experiments were conducted over a two year period in soil columns packed uniformly with sandy loam or loamy sand. A series of experiments were conducted in bare soil, followed by repeated experiments with wheat plants in the columns, and finally in bare soil again after the wheat crop had died. The loamy sand columns showed significantly higher dispersion than the sandy loam columns in the precrop experiments, but the effective dispersion decreased when the experiments were repeated with plant roots present. The post crop experiment showed the highest dispersion of any of the studies possibly due to the presence of old root channels in the soil. Very little immobile water was present in the precrop experiments, but both the cropped experiments and the post crop experiments exhibited significant pore bypass; immobile water fractions ranged from 11 percent to 39 percent of the total water content.

Rainfall characteristics and their relation to splash erosion

Abstract: THIS study involves the mathematical development of both analytical relationships for raindrop size distributions and terminal and fall velocities of raindrops. Results compared satisfactorily to observed data from several references. From the above relationships, storm energy and momentum parameters were simulated and then related statistically to rainfall intensity. Splash erosion rates are a function of rainfall intensity. It was found that rainfall parameters had a significant effect upon splash erosion.

A Simplified Technique for Measuring Raindrop Size and Distribution

Abstract: A simple technique for measuring raindrop size and distribution is presented. This technique, the Oil Method, has the advantage of being a direct measurement technique that requires no calibration and no special equipment except a camera. The authors found the technique to be easy to use both in the laboratory and in the field. Examples of the use of the method for determining the raindrop characteristics of simulated and natural rainfall are presented

A soil-tool model based on limit equilibrium analysis

Abstract: A mathematical model for predicting the behavior of narrow tillage tools in soils is based on a limit equilibrium analysis. Pertinent soil, tool and interface parameters influencing the tool performance have been identified and incorporated in the model. A comparison of predicted and experimental results is also included. Mathematical models based on emperical as well as semi-emperical methods have been developed to describe the soil-tillage tool interaction (Payne, 1956; Hettiaratchi and Reece, 1967; Hettiaratchi et al., 1966; Osman, 1964; Godwin and Spoor, 1977; McKyes, 1978; Desai et al., 1981). Even though the soil-tool interaction problem is three dimensional in nature, a majority of the models available are based on two-dimensional consideration (Hettiaratchi et al., 1966; Osman, 1964; Payne, 1956). In recent years some progress has been made toward the development of three dimensional models (Hettiaratchi and Reece, 1967; Godwin and Spoor, 1977; McKyes, 1978). However, most of these models are complex, and a sound mathematical background is essential to utilize them. Thus the need exists for more general and less complex models capable of predicting tillage-tool behavior in soils. Unlike costly experimental procedures, availability of such models would permit designers as well as researchers to develop with minimum effort a clear understanding of soil-tool interaction through parametric studies. Therefore, the overall objective of this study was to develop a generalized mathematical model and to examine its validity for predicting the tillage tool performance in soils..

Compressibility and Frictional Coefficients of Wheat

Abstract: TWO grain pressure parameters, bulk density and the sidewall friction coefficient, were evaluated for soft red winter wheat Functional relationships were developed for the grain parameters as they were allowed to vary with the internal pressure of the grain, speed of travel of the grain down the sidewall, and the moisture content of the grain These parameters were allowed to vary over a range of 7 to 172 kPa, 006 to 6 m/h and 8 to 24% wet basis moisture content, respectively

Soil Erodibility Variation During the Year

Abstract: SIX years of data from erosion plots at Holly Springs, MS, and 10 yr of data from plots at Morris, MN, were used to study variation in soil erodibility through the year. Monthly values of soil erodibility were related to time with a cosine curve. Erodibility varied from a high of 169% of annual average K (K of the Universal Soil Loss Equation) on February 4 to a low of 31% of annual average on August 5 for the Mississippi data. Minnesota erodibility data were described similarly except the maximum and minimum of the erodibility function lagged the Mississippi curve by about 2 months. It was suggested that erodibility could be predicted using a variability function based on normal air temperature data described by a cosine function and average annual K factor values.

Shade Management Systems to Reduce Heat Stress for Dairy Cows in Hot, Humid Climates

Abstract: THE benefits of providing shade for dairy cows are reported based on over 8 yr of research. Production benefits that are attributable to a well-designed shade management system are increases in milk production, reproductive efficiency and milk production in subsequent lactation. Major design and management considerations for shade management structures that are presented and discussed are orientation, space, floor, height, ventilation, roof construction, feeding and watering facilities, and waste management system.

The Thermal Properties of Tomato Juice Concentrates

Abstract: A probe system was prepared and calibrated for the accurate thermal conductivity and thermal diffusivety measurement in food products for the temperature range of 20 C to 150 C and for a range of composition from 4.8 to 80 percent total solids. Thermal conductiv-ties, thermal diffusivities and specific heats of tomato joice and soilds were found to increase with increase in temperature and water content. Density of tomato juice decreased with increase in temperature and decreased with increase in water content. However, density of tomato solids did not change significantly with increase in temperature. Mathematical models were developed to predict the thermal conductivity, thermal diffusivity, density and specific heat of tomato juice at various water contents and various temperatures and compared to the values experimentally determined from the line heat source technique.

Remote Sensing of Soil Moisture with Microwave Radiometers

Abstract: Results are presented that were derived from measurements made by microwave radiometers during the March 1972 and February 1973 flights of National Aeronautics and Space Administration (NASA) Convair-9900 aircraft over agricultural test sites in the southwestern part of United States The purpose of the missions was to study the use of microwave radiometers for the remote sensing of soil moisture The microwave radiometers covered the 08- to 21-cm wavelength range The results show a good linear correlation between the observed microwave brightness temperature and moisture content of the 0- to 1-cm layer of the soil The results at the largest wavelength (21 cm) show the greatest sensitivity to soil moisture variations and indicate the possibility of sensing these variations through a vegetative canopy The effect of soil texture on the emission from the soil was also studied and it was found that this effect can be compensated for by expressing soil moisture as a percent of field capacity for the soil The results were compared with calculations based on a radiative transfer model for layered dielectrics and the agreement is very good at the longer wavelengths At the shorter wavelengths, surface roughness effects are larger and the agreement becomes poorer

Erosion of Soil and Poultry Manure— A Laboratory Study

Abstract: THE transport of soil and manure by simulated rainfall on 1 m X 0.64 m laboratory test plots was investigated to determine the effects of rainfall intensity, soil type, manure type, loading rate and drying time. A factorial experimental design was used with each factor at two levels. As expected, rainfall intensity and soil type were significant factors for solids transport, and manure loading rate was a significant factor for nutrient transport. Manure type and drying time were also significant factors for transport of certain nutrients. Overall, several factors and their interactions had significant effects on erosion and transport of soil, manure and nutrients. This indicates that prediction models of erosion and nutrient transport from areas receiving manure should consider several factors, including manure type, manure loading rate, and time between application and rainfall

Physical and Chemical Properties of Eroded Soil Aggregates

Abstract: RAINFALL simulation was used to evaluate the characteristics of aggregates eroded from erosion plots on two loess soils in southwestern Iowa. The mean aggregate diameters (D50) for interrill erosion were 44 and 34 ^m for soils with 26% clay and 1.9% carbon and 22% clay and 0.8% carbon in their matrix, respectively. The D50 size increased as rilling occurred, but the percentage of increase was quite different for the soils. The D50 size increased by 91% for the soil with higher clay, whereas it increased by only 15% for the other soil. The eroded aggregates >50 ^m in diameter contained more clay and total nitrogen than did the aggregates im, when analyzed as a single fraction. The >50-/im aggregates were also enriched in clay and nitrogen when their contents were compared to those of the matrix soil. Enrichment was greater for interrill than for interrill plus rill erosion because of greater particle selectivity during the transport process. Equilibrium phosphorus concentration curves varied with aggregate size, suggesting that 250 to 50-jum aggregates are of greater importance in buffering soluble P levels and transporting labile P than larger aggregates...

Kentucky Rainfall Simulator

Abstract: THE construction and operating characteristics of the Kentucky Rainfall Simulator, a new, highly portable rainfall simulator, is described. It is a nozzle type simulator and is suitable for both large- and small-scale studies of the erosion, infiltration, and runoff processes. The simulator closely approximates the kinetic energy of natural rainfall at intensities greater than 25 mm/h. Rainfall intensities ranging from 3.5 to 185 mm/h can be produced, and measured uniformity coefficients range from 80.2 to 83.7. Runoff and sediment sampling devices used with the Kentucky Rainfall Simulator are also described.

Slope Steepness and Incorporated Residue Effects

Abstract: A controlled field experiment was conducted to determine the effect of slope steepness and incorporated residue on rill erosion. Duplicate rills were tested on slopes of 9, 18, and 23%, each with incorporated wheat straw residue of about 0, 4700, and 9400 kg/ha. Rill erosion was shown to vary directly with flow shear stress, but rill geometry depended on other processes. The medium and high residue rates reduced rill erosion to 40 and 15% of the no-residue condition, respectively, which provides guidelines for the USLE C-factor.

Dielectric Properties of Some Fresh Fruits and Vegetables at Frequencies of 2.45 to 22 GHz

Abstract: DIELECTRIC-CONSTANT and loss-factor values for potato, sweet potato, peach, watermelon, cantaloupe, and cucumber tissue at frequencies of 2.45, 11.7, and 22.0 GHz are reported, along with data on the moisture content, density, and soluble solids content of the fruit and vegetable tissues. Correlations were noted between the dielectric properties of the different tissue types and their moisture contents. The frequency dependence of the dielectric constant and the loss factor indicate that the dominant dielectric relaxation frequencies for fresh fruit and vegetable tissues lie either between 2.45 and 11.7 GHz or below this frequency range. Since this behavior is contrary to expectations, loss-factor values need to be checked by other measurement techniques.

Characteristics of Raindrop Throughfall Under Corn Canopy

Abstract: A laboratory rainfall simulator was used to study the raindrop size and velocity under a corn canopy. Drop sizes were measured by using a dye-paper technique, and drop velocities were measured photographically. Stemflow was calculated on the basis of rainfall under the canopy and incident rainfall above the canopy. Up to 49% of incident rainfall appeared as stemflow. Drops that directly penetrated the crop canopy accounted for much of the throughfall kinetic energy; drips from leaf margins also contributed greatly to throughfall kinetic energy. Drops that splashed from leaves were quite small and contained little kinetic energy. The ratio of the kinetic energy at ground level to kinetic energy at the top of the canopy was compared with the ratio predicted by Wischmeier and Smith (1978) for use in the Universal Soil Loss Equation. The comparison indicated little difference between what we observed and that predicted.

Evaluation of a Water Management Model for Irrigated Agriculture

Abstract: DRAINMOD is a computer model simulating the movement and storage of water in soils with a shallow water table in the humid region. It was developed for the comprehensive analysis of soil water transformation on a field scale where most water management facilities are designed and installed as a single unit. The basis of DRAINMOD is a water balance at midpoint between two parallel drains. Using the approach of successive steady state equilibrium, the unsteady and transient water movement in a tile drained field is analyzed as steady state flow at sufficient small time increments. The reliability of the model for irrigated cropland in semiarid climate was tested with field data from California. Water table elevations predicted by DRAINMOD agreed reasonably well with measurements for five experimental locations differing in soil texture in the San Joaquin Valley and the Imperial Valley. Water loss by deep seepage ia a significant component in soil water balance from irrigated cropland. When the water table drawdown exceeds 150 cm, the model tends to over estimate the depth to the water table.

Evapotranspiration from a Humid-Region Developing Citrus Grove with Grass Cover

Abstract: EVAPOTRANSPIRATION (ET) of a developing citrus grove in a humid climate in the Flatwoods Land Resource Area was determined by water balance from measured rainfall, irrigation, subsurface drainage, surface runoff, and the change in soil moisture storage. The change in soil moisture storage was estimated from soil moisture characteristic curves and measured water table elevations. Annual ET ranges from 820 to 1280 mm and averaged 1090 mm across all treatments. When soil moisture was not seriously limited the annual ET averaged 1210 mm. Linear regression of ET vs time indicated a significant increase of 13% in ET over the 8 years of the study. This increase was attributed to increasing tree size since the grass understory was maintained to provide similar cover conditions throughout the study. Daily ET rate, averaged by months, ranged from 1.5 mm in January to 5.0 mm in June. Four predictive equations for ET gave good estimates of measured values, but require crop coefficients that are slightly modified from previously published values.

Drip Irrigation Application Efficiency and Schedules

Abstract: THE application efficiency of a drip irrigation system can be estimated from the emitter flow variation caused by hydraulics alone or by the hydraulics and man-ufacturer's variations combined. The application effi-ciency for the cases when the field has been irrigated to the established irrigation requirement and when a field is irrigated with some soil moisture deficiency were ana-lyzed. An irrigation time schedule can also be calculated based on the total irrigation water requirement with or without deficit, the total actual discharge of the drip ir-rigation system, and the irrigation application efficiency. Deficit irrigation can increase irrigation application effi-ciencies to as high as 100 percent. The deficit area (sur-face area) and the average depth of deficit in the deficit area can be calculated from the coefficient of variation of emitter flow and total percentage of deficit (related to the total volume of water required). This study relates drip irrigation design and schedule to a deficit irrigation situation which the crop can tolerate without affecting the yield significantly.