ASAE Standards Research Articles

Preliminary Evaluation of Drip Irrigation System Performance in Watermelon Cultivation

In watermelon production, irrigation is the most significant factor in achieving good yields. Properly selecting an irrigation system may provide successful irrigation for excellent crop quality and productivity. Drip irrigation is a popular approach for this purpose. Drip irrigation can successfully deliver water to plants based on the amount required by the crop. However, this irrigation system's performance should be investigated to guarantee that it can run in the best possible conditions. This study aimed to assess the preliminary version of drip irrigation for watermelon crops. The field experiments were conducted on a watermelon planting plot at MARDI Kundang Selangor. The drip irrigation system performance was evaluated based on hydraulic parameters such as coefficient uniformity (CU), emission uniformity (EU), coefficient of variation (CV), and emitter flow variation (EFV) according to ASAE standards. The results indicate that CU is in excellent classification, with a CU efficiency greater than 91 per cent. The EU value was 86%, showing a reasonable variety. However, the CV value was 0.1, indicating a marginal classification. Meanwhile, the emitter flow variation (EFV) is 19% which is considered acceptable. The results of this preliminary study showed that the performance of this drip irrigation system is satisfactory, as the hydraulic parameters evaluated met the ASAE standard's minimum classification requirements. The distribution of discharge data was similarly shown to have no significant difference using a one-sample t-test, with a p-value of 0.096.

Physical Properties of Ginger Based on Different Varieties

Ginger is a plant recently gaining attention in the food and pharmaceutical industries because of its spice and medicinal importance. The measurements of physical properties were conducted at the Food Processing Laboratory, Kelappaji College of Agricultural Engineering and Technology in Tavanur Kerala. The physical and engineering properties of different ginger varieties viz., Athira, Aswathy, Chithra and Karthika were determined to design the hopper and cell sizes, better flowability in the hopper without any clogging in the electronic seed metering unit of a sensor-based tractor drawn ginger planter. The research looked at some physical properties of ginger (Zingiber officinale) rhizomes such as major, minor, intermediate diameters, geometric mean, sphericity, bulk volume, bulk density, surface area, angle of repose and coefficient of friction which are essential for the design of hopper. The properties were determined using ASAE standards. The average value obtained for ginger rhizomes those are, major diameter, minor diameter, intermediate diameter, geometric mean, sphericity, surface area, bulk density, bulk volume, moisture content and angle of repose of the different varieties of the ginger rhizomes are geometric mean of the athira variety of ginger having major diameter is 69.72 mm (X), intermediate diameter is 20.6 mm (Y), minor diameter is 51.84 mm (Z). Geometric mean is 40.24 mm, Sphericity is 0.58, Surface area is 5086.5 cm2, Bulk density is 0.43 g/cm3, 24 cm3, Moisture content is 71.1%, and angle of repose is 34.43̊ respectively. The coefficient of friction was obtained three different structural materials, the obtained values are 0.58 on wood, 0.52 on mild steel and 0.48 on stainless steel. Aswathy variety of ginger having major diameter is 88.96 mm, minor diameter is 53.84 mm, intermediate diameter is 20.92 mm, Geometric mean is 44.02 mm, sphericity is 0.50, surface area is 6240.2 cm2, bulk volume is 25 cm3, bulk density is 0.38 g/cm3, moisture content is 74.53 % and angle of repose is 36.87̊ and obtained values of the coefficient of friction was 0.60 on wood, 0.58 on mild steel and 0.50 on stainless steel. Chithra variety of ginger having major diameter is 81.2 mm, minor diameter is 55.32 mm, intermediate diameter is 18.64 mm, geometric mean is 41.88 mm, sphericity is 0.52, surface area is 5571 cm2, bulk density is 0.43 g/cm3, bulk volume is 40 cm3, moisture content is 72.45 % and angle of repose 36.54̊ . The obtained values of the coefficient of friction were 0.54 on wood, 0.51 on mild steel, 0.46 on stainless steel. Karthika variety of ginger having major diameter is 85.08 mm, minor diameter is 49.8 mm, intermediate diameter is 17.2 mm, geometric mean is 38.96 mm, sphericity is 0.48, surface area is 5078 cm2, bulk volume is 20 cm3, bulk density is 0.38 g/cm3, moisture content is 76.01, angle of repose is 38.24̊, and coefficient of friction were 0.59 on wood, 0.53 on stainless steel and 0.45 on stainless steel respectively.
 Based on the physical properties of ginger, it was concluded that above mentioned parameters are sufficient to design the hopper and cell sizes are suitable for the mechanical planters or any other sensor-based tractor drawn ginger planters. All the physical properties of ginger based on varieties are measured and showed in this research.

Employing Data Mining Algorithms and Mathematical Empirical Models for Predicting Wind Drift and Evaporation Losses of a Sprinkler Irrigation Method

The advantage of a sprinkler irrigation method is that it saves up to 50% of water consumption during the application of water, as compared to any other surface irrigation system. To assess the behavior of a sprinkler irrigation method, wind drift and evaporation losses (WDEL) are often employed as important parameters. The predictive capacities of four previous mathematical empirical models and two data mining algorithms, namely, reduced-error pruning tree (REPTree) and artificial neural network (ANN) models, were employed to evaluate the impact of the operating parameters of a sprinkler irrigation method on WDEL. The inputs to the REPTree and ANN models were the working pressure, vapor pressure deficit, air temperature, wind speed, nozzle diameter, and air relative humidity. In the experimental field, for data collection, a solid set of sprinklers and collectors positioned per ASAE standards was employed. Promising results showed remarkable performance for one of the mathematical empirical models tested, with a confidence index value of 0.829. Meanwhile, the REPTree and ANN models presented smaller errors for testing data set and are qualified for use given their confidence index values of 0.956 and 0.964, respectively. The REPTree and ANN algorithms were classified as optimal models, indicating that the use of mathematical experimental models alone is inadequate in operational situations involving the nozzle diameter, working pressure, and other variables.

Estimating Battery Size Requirements for Tractor Electrification of Row-Crop Planting Operations

Highlights Calculate and compare engine power needed for row-crop planting from ASAE standards and reported CAN data. Estimate energy requirements and the equivalent electric battery’s volume and mass for row-crop tractor. Discuss the feasibility for electrification of a fully electric row-crop tractor. Abstract. Power sources such as batteries, used for both on-road and off-road vehicles, are advancing at a rapid pace. Electric batteries are becoming more power dense, thus allowing them to be used as a power source to replace previous diesel or gasoline-powered systems. Efforts are underway to transition off-road agricultural vehicles from Internal Combustion Engine (ICE) vehicles to electric vehicles (EVs); however, the energy requirements of typical agricultural field operations need to be fully understood before such a transition can occur. Theoretical prediction equations available in the American Society of Agricultural and Biological Engineers (ASABE) standards or the use of engine load data from a tractor’s Controller Area Network (CAN) bus are two methods for determining the energy demands of implements on tractors. In this study, tractor CAN bus data was collected from multiple no-till corn planting operations to estimate the energy requirements of the planting operation in kWh. The estimated energy requirement was used to determine the equivalent physical mass and volume of a lithium-ion battery needed to power a hypothetical fully electric tractor for comparable planting operations. The estimated battery capacities using the worst-case field-use scenario in this study were 1117 kWh for operating a 16-row planter to plant 68 ha (168 acre) in a day at an average ground speed of 8.6 km h-1 (5.4 mph) for 14 hours, and 2658 kWh for operating a 48-row planter to plant 158 ha (391 acre) in a day at an average ground speed of 8.9 km h-1 (5.6 mph) for 15 hours. Given the current battery energy density requirements, the equivalent battery masses and volumes were found to be 5,319 kg and 3.33 m3, 12,657 kg and 7.93 m3, for 16-row planter and 48-row planter, respectively. These high kWh estimates needed to power future fully-electric tractor power units are based on worst-case scenarios that could be encountered in real field operations that use wide planters over long operating hours. Keywords: Battery, Controller Area Network, Electric Vehicles, Electrification, No-till, Planting, Row-crop, Tractor.

Potential of Dimensional Measurements of Individual Pellets for Evaluating Feed Pellet Quality

HighlightsPellet length but not width increased significantly with increasing inclusion of a pellet binder in a pelleted feedMachine vision capably and rapidly measures pellet lengthThe narrow range in pellet length measurements prevents its use as an effective discriminator of pellet qualityPellet durability index from aggressive pellet durability testing is the better discriminator of feed pellet qualityAbstract. Pellet durability index (PDI) detailed in ASAE Standard S269.4 (ASAE Standards, 2007) has been the widely accepted measure for pellet quality in the U.S. and, by extension, the measure for evaluating the effect of ingredients and pelleting process variables on the quality of pelleted feed products. The PDI is calculated as the mass percentage of intact pellets remaining after tumbling a 500 g sample in a tumbling can durability tester for 10 min. In the case where pellet quality is good, oftentimes the resulting PDI for different experimental treatments are very close in magnitude. In these situations, it is desirable to have another measurement that would allow for finer discrimination among treatments. It was hypothesized that the average linear dimensions of animal feed pellets in a unit mass sample would vary as a function of formulation and pelleting process variables for a consistent knife setting in the pellet mill. This hypothesis was tested in a study involving effectiveness testing of varying inclusion levels of a potential pellet binder in a typical corn-soy swine diet pelleted by both conventional and cold pelleting processes. Pellet lengths and diameters measured by a machine vision implemented in ImageJ matched to measurements taken manually and varied with treatments. Pellet length varied with treatments but could not be a good discriminator of pellet durability between pelleted products because of the narrow range in measurement numbers (8.53 to 11.15 mm by machine vision). With the wider range in numerical values of the PDIs obtained through aggressive durability testing (23.0% to 81.0% in a tumble can with steel hexagonal screw nuts versus 91.0% to 97.5% in a tumble can without hexagonal nuts), PDI from aggressive testing is the better discriminator of quality among pelleted products because of its greater resolution. Keywords: Animal feed, Durability, Linear dimensions, Machine vision, Pellet, Pellet binder, Pelleting, Quality.

Design, Development and Evaluation of a Bucket Drip Irrigation System for Dry Season Vegetable Production in South-Eastern Nigeria

In South-Eastern Nigeria, during the dry season from November to April, vegetables are always in short supply and consequently expensive. Hence, there is a need to design, develop an affordable and simple bucket drip irrigation system that can be used to grow vegetables under limited water supply conditions. Using the estimated consumptive use of the proposed crop okra and the area occupied by the crop stands, the capacity of the bucket as a source of water was computed. The bucket filled with water was placed at a head of 1 m. The water was allowed to flow through emitters located at 30 cm intervals along the lateral lines laid at the land slope of 2%. Two lengths of PVC tubes 11 m long, 1 mm thick and internal diameters 16 mm, Micro-tubes 5 cm long and internal diameter 1.2 mm, were used. The discharge from each emitter was determined through volumetric measurements. The system was then evaluated using the Christiansen’s method and the Merriam and Keller’s method and assessed using ASAE standards 1996(a) and 1996(b) performance rating. 22 sampled emitters evaluated from the lateral line showed total energy drop of 2.5 x 10-5 m, flow variation (FV) of 8%, coefficient of variation (CV) of emitter discharge of 0.02, uniformity coefficient (UC) of 97% and emission uniformity (EU) of 73%. The results show that the system is efficient and can be used by farmers to meet the demands for vegetables in the dry season.

Optimization of tillage and sowing operations using discrete event simulation

A simulation model was developed for secondary tillage and sowing operations in autumn, using discrete event simulation technique in Arena<sup>®</sup> simulation software (Version 14). Eight machinery sets were evaluated on a 50-hectare farm. Total costs including fixed-costs, variable costs and timeliness costs were calculated for each machinery set. Timeliness costs were estimated for 21-years period on daily basis (Daily Work method) and compared with another method (Average Work method) based on the equation proposed by ASAE Standards, EP 496.3FEB2006. The Inputs of the model were machinery sets, field size, machines performances and daily soil workability state. The optimization criteria were the lowest costs and lowest standard deviation in daily work method plus the lowest costs based on average work method. The validity of the model was evaluated by comparing the output of the model with field observed data collected from various farms. Results revealed that there was no significant difference (P > 0.01) between the observed and predicted finish day.

Economic competitiveness gap related to the application of the GAEC standards of cross-compliance on farms: evaluation methodology

This paper describes the methods used in the monitoring carried out in the farms of the MO.NA.CO. project, to calculate the economic competitiveness gap faced by agricultural holdings that accede to the commitments imposed by the standards included in the project. The monitoring works were performed in agricultural holdings in relation to the particular reference condition of each standard. The processing of the information acquired allowed us to define the working times of each cultivation operation by means of the indications in the recommendations of the Associazione Italiana di Genio Rurale - Italian Rural Engineering Association, that considers the official methodology of the International Commission of the Organisation Scientifique du Travail en Agriculture (C.I.O.S.T.A.). The overall costs and revenues in case of compliance or non-compliance with the commitments of the standard were calculated by using Biondi’s methodology and other norms that indicate the technical and economic coefficients to be used in the calculations (EP 496.2 and D 497.4 ASAE standards). With the data related to the unit cost of ploughing a model Partial Least Squares (PLS) has been achieved and validated, and it makes possible to predict the unit cost of this agricultural operation. Finally, the values of the variation of the economic competitiveness gap are reported for each standard.

Development of a fuel consumption equation: Test case for a tractor chisel-ploughing in a clay loam soil

Fuel consumption and tillage draught were measured when chiselling in a clay loam soil in Badjgah Research Station, Shiraz University, Shiraz, Iran. An 81 kW tractor (MF-399) instrumented with a data acquisition system was used to measure fuel consumption, actual forward speed, theoretical forward speed, slip and implement draught. The effects of blade width (5 and 10 cm), tillage depth (10, 15 and 20 cm) and actual forward speed (3, 4 and 5 km h−1) upon fuel consumption were investigated. Fuel consumption was assumed to be a function of wheel numeric, slip, net traction ratio, rolling resistance ratio, chisel-tool aspect ratio and actual forward speed. Collected data were used to model the tractor fuel consumption using dimensional analysis approach. Results were compared to fuel consumption rates as predicted by ASAE Standards (D497.4). The comparisons showed that the standard overestimates fuel consumption by 26–53%. Results from regression (F-test) between predicted and measured fuel consumption data showed that the slopes for fuel consumption with the 5 and 10 cm blade widths were not significantly different from 1:1 line (P ≤ 0.05). Consequently, the fuel consumption rate can be successfully predicted by the model with good accuracy.

Spray Classification for Selected Flat Fan Nozzles

The flat fan nozzles made by Mikolajczak Agro Technology Company (MMAT) (standard RS, and pre-orifice AZ), in the ISO sizes of: 02, 03, and 04 were evaluated. The spray quality parameters: D V10 , D V50 , D V90 , and RS, in the working pressure range of: 150, 300 and 450 kPa, were determined. The coefficient of volume fraction droplets smaller than 100 µm was also calculated. The spray classification of MMAT nozzles was defined according to ASAE standards. This information should be useful for the sprayer operator when making a selection of a field sprayer's working parameters according to the pesticide use guide.

Proctor cone penetrometer for in-situ soil strength studies in Nigeria

A bstract: Investigations of in-situ or laboratory soil strength properties, particularly the resistance of soil to penetration, usually referred to as cone index (CI) are often required in soil tillage and traction studies. ?This helps in the analysis of the interactions of both tillage tools and tractive elements with the soil. ?However, penetrometer, the instrument used for measuring this important parameter (CI), is not readily available in Nigeria. ?Following the recommendations in ASAE standards, a functional proctor cone penetrometer for soft soils has been developed and calibrated. ?The major parts include the handle, made of half-inch galvanized pipe, constructed in such a way that it can be screwed on and off the pressure shaft conveniently, the graduated pressure and penetration shafts made of stainless steel; the spring loaded pressure chamber, and a cone probe. ?The penetrometer was calibrated by applying known forces on the handle while noting corresponding penetrations and displacements on the graduated pressure shaft. ?A performance test was carried out on a clayey loam soil to compare the readings obtained from the developed penetrometer and an imported one. ?The major difference between the two is that while one is very expensive and scarce to come by, the other is produced locally with locally sourced materials and technology. ?The cost of the imported one is ten times more than that of the local one. ?The mean CI obtained for twenty-four random samples on the soil surface for the test area at 18 cm depth was found to be 1.4358 MPa for the local, and 1.5096 MPa for the imported.? Regression analysis of the two sets of values of CI for the local and the foreign showed a strong correlation ( R 2 = 0.779, P <0.05). ?This implies that the locally produced proctor penetrometer is reliable for measurements of CI at 0

SURFACE IRRIGATION PERFORMANCE IN THE UPPER TUNUYÁN RIVER BASIN MENDOZA, ARGENTINA

The irrigated area in the Upper Tunuyan River Basin comprises 41,601 ha with surface irrigation rights. It is, therefore, essential to develop indicators to determine irrigation water use efficiency -which will, in turn, help to detect the main problems and find solutions for the sustainable development of the basin. The overall objective of this study is to obtain information on irrigation water use within the agricultural properties in the command area of the Upper Tunuyan River and to determine the potential efficiencies to be achieved considering possible operational changes and salt balance. Surface irrigation methods, with and without tailwater runoff, prevail in the basin. Walker and Skogerboe's methodology (1987) and the ASAE standards (1999) were used. Soil and irrigation characteristics include: furrow irrigation with runoff; sandy-loam soil textures; 0.87% slopes; soil salinity from 0 to 100 cm: 1.12 dSm -1 ; irrigation water salinity: 0.70 dS m ; managed and unit flows of 53 L s -1 and 1.24 L s -1 m -1 respectively; 123 m long irrigation plots; 7-h application periods; and 5.3 mm h -1 basic soil infiltration. The following results were obtained: on-farm irrigation efficiency; and conveyance, application, storage and distribution efficiencies: 91, 43, 99 and 91%, respectively. Potential efficiency may rise to 68% if plot irrigation management is improved; it may well be higher than 68% if the salt balance is taken into account.

Effect of varying the distance of collectors below a sprinkler head and travel speed on measurements of mean water depth and uniformity for a linear move irrigation sprinkler system

A series of sprinkler irrigation uniformity tests were conducted to determine the effect of collector height and speed on applied water depth and uniformity from a linear move sprinkler irrigation system. Collectors, 102 mm in diameter and 200 mm in height, were set in the field according to the method outlined by ASAE [(2001). American Society of Agricultural Engineers. Test procedure for determining the uniformity of water distribution of center pivot and lateral move irrigation machines equipped with spray or sprinkler nozzles. ASAE Standards, ANSI/ASAE S436.1 MAR01] test procedures. The sprinkler system used in the study was a fixed plate sprinkler head with a 180° wetting pattern. Catch devices were placed to 300, 600, 900, and 1200 mm heights above ground and tested with 15 and 30 m h−1 speeds. The results indicated that mean sprinkler irrigation depths ranged from 45.5 to 51.4 mm and from 21.3 to 25.9 mm for 15 and 30 m h−1 system speeds, respectively. Mean coefficient of uniformity (CU) values for the same speeds ranged from 89.4% to 92.6% and 88.9% to 95.1%, respectively. Both irrigation water depth and CU measurements were significantly affected (p<0.05) by collector height but halving the irrigation system speed, apart from producing the expected doubling in water depth, produced no significant effects. Differences in collector heights could cause differences in irrigation depth and CU values of as high as 10 mm and 6%, respectively.

Development of a Visual Method to Test the Range of Applicability of Thin Layer Drying Equations Using MATLAB Tools

Thin-layer drying equations are important in crop drying simulations. Various drying theories based on semi empirical Newton model or diffusion model are employed to predict crop drying. The Page model that is an empirical variation of Newton model has gained popularity due to its simple form yet robustness. The drying equations summarized in the revised ASAE standards S448 are mostly based on Page's model. The MATLAB based software TLDRY is developed to examine the range of applicability of equations in ASAE S 448 and a number of other thin layer drying equations found in literature. The software proved to be a convenient tool to identify the range of applicability of and potential uncertainties for these equations.

Sorption isotherms for amaranth grains

Compiling of EMC–ERH data for amaranth grains ( Amaranthus cruentus L.) in the range of water activity from 0.029 to 0.979 and temperature from 25 to 90 °C was performed. Included data sets comprised experimental values of EMC–ERH that summarize 78 identified points for desorption, 53 for adsorption and 16 not discerned points that were considered for mean sorption. Five isotherm equations for grains included in the ASAE Standards (Modified Henderson, Modified Chung–Pfost, Modified Halsey, Modified Oswin and GAB) were evaluated for their ability to fit sorption data from the literature ( M e vs. a w for adsorption, desorption and mean sorption). The goodness of fit for each isotherm was quantified through the correlation coefficient ( R 2), the sum of squares (RSS), the standard error of the estimate ( S y ), the mean relative deviation (MRD) and the plots of residuals. The three-parameter GAB isotherm was the best and gave a good correlation ( R 2 > 0.9817, RSS < 0.0293, MRD < 0.1380, S y < 0.0141, and random residuals-plots) for the general data-fit in the range of a w from 0.1 to 0.9, of interest in seed storage and processing. The Modified Halsey equation was rejected because it gave poor statistic parameters of agreement and patterned residual plots. For desorption, the Modified Chung–Pfost model gave the lowest mean relative deviation; the Modified Henderson equation was the second best in describing the EMC–ERH data, followed by the Modified Oswin and GAB models. For adsorption, the GAB equation presented the lesser MRD, followed by the Modified Chung–Pfost, Henderson and Oswin models. When mean sorption data were analyzed, the Modified Chung–Pfost equation was the best. However, when the GAB isotherm was adjusted at each temperature, a higher quality of agreement was obtained compared with the other isotherms, demonstrating the adequacy of GAB model to describe the experimental data of EMC–ERH for amaranth.

Modelling of power and energy requirements for tillage implements operating in Serdang sandy clay loam, Malaysia

Information is required on power and energy requirements for tillage implements. Draught and energy requirement measurements were made with an instrumented tractor for mouldboard ploughing, disk ploughing, disk harrowing and rotary tilling in the Serdang sandy clay loam soil. The effects of travel speed and tillage depth or rotor speed upon the measured draught and power requirements were investigated. Four polynomial draught and power models from orthogonal regression analyses were formulated based on linear and quadratic functions of travel speed and tillage depth or rotary tiller bite length. The predictions by the draught models developed for the mouldboard plough and the disk harrow were within the ranges of draught recommended by ASAE Standards D497.3. A comparison of the draught model for the disk plough and power model for the rotary tiller with the ASAE Standards D497.3 could not be made simply because these guidelines are not listed therein. Four linear fuel consumption models from regression analyses were also formulated based on drawbar power or PTO power as well as equivalent PTO power. Fuel consumption rates predicted by ASAE Standards D497.3 were found to be 17–33% overestimates of the values predicted by the statistical models developed from measurements. However, fuel consumption rates reported by OECD Tractor Test were found to be 94–109% of the values predicted by the models developed. From 37 to 52% of the measured fuel consumption for the various ploughing operations was required to propel the tractor, and the remainder was used for the actual task of working the soil. Finally, average draught, fuel consumption, wheel slip, drawbar power, tractive efficiency and overall energy efficiency for draught implements as well as average PTO power, fuel consumption, wheel slip, wheel power and specific energy for powered implement are presented. The disk harrow was the most energy efficient implement in terms of fuel consumption and specific energy, followed by the rotary tiller, disk plough and mouldboard plough. These obtained results will be helpful to develop comprehensive information on power and energy requirements of tillage implements for the formulation of Malaysian agricultural machinery management database.

A LITERATURE REVIEW OF SWINE HEAT PRODUCTION

Current ASAE standards of heat and moisture production (HP, MP) for swine are primarily based on data collected nearly four decades ago. Feedstuffs, management practices, growth rate, and lean percentage of swine have changed HP and MP considerably in that time period. Literature data shows that lean percent increased 1.55% in the last 10 years, resulting in an increase in HP by approximately 15%. Data were compiled into two categories: prior to 1988, and 1988 to present. Analysis of this data revealed that HP increased 12.4% to 35.3% between the two categories, with the largest differences occurring at higher temperatures. The results also revealed lack of HP and MP data for greater than 90 kg pigs. The HP and MP standards for design of swine housing systems should be updated.

Analysis of field machinery performance based on daily soil workability status using discrete event simulation or on average workday probability

The objective of the study was to develop a simulation model for field machinery operations using a discrete event simulation technique in order to analyse machinery performance based on daily status of soil workability for a series of years ( Daily Work. method), and to compare the results with those from a simpler method based on average probability values of available workdays for operations and seasons ( Aver. Work. method). Timeliness costs with this latter method were estimated using the formula proposed by ASAE Standards, ASAE EP496.2 DEC99. Seven machinery sets were assessed on a 400 ha farm with both methods in terms of total costs (labour+specific machinery+timeliness costs) to find the effect of the methods on assessment of timeliness costs. The model for field machinery operations was developed in the Arena simulation language, allowing simulation of field operations on a real farm for a 20-year period. Completion dates of operations in individual fields were important outputs of the model, which enabled timeliness costs to be estimated in detail. Daily soil workability was inferred by means of moisture thresholds from simulated soil moisture contents from another model (the SOIL-model) and weather data from Uppsala, Sweden. The validity of the machinery model was tested with data from a farm, the daily results of the model had good agreement with the progress of the field operations at the real farm. The assessment of the seven machinery sets revealed that machinery costs were the main component of total costs and, as expected, they increased with machine size. Labour costs and timeliness costs decreased as machine size increased with both methods. The Aver. Work. method estimates resulted in lower timeliness costs for sowing operations than those determined with the Daily Work. method, which was attributed to the fact that former method did not take into account chain effects. Regarding timeliness costs for harvesting operations, the Aver. Work. method was considered inappropriate because of scattered field maturity times in the region of the study where single periods with their own optimum time are difficult to identify. In addition, the ASAE formula was very sensitive to the number of such periods. In contrast, timeliness costs with the Daily Work. method were estimated for sowing and harvesting operations taking into account some management criteria and chain effects were captured on a field basis. They were quantified for sowing and harvesting operations based on a long-term assessment (20 years) and their yearly variability was determined.

Assessment of Iowa farmers' perceptions about auger safety.

A survey of Iowa farmers was conducted to assess the farmers' perceptions and beliefs regarding auger safety and how these perceptions are put into practice. A questionnaire was designed to obtain information on the following auger-related topics: recognition of safe practices and appropriate shielding, personal practices and behaviors, risk perception, and personal beliefs. A random sample of 400 Iowa farmers (arrayed by county) was selected to be representative of Iowa farms. The response to the mailed survey was 23%. Some returned surveys were eliminated because the respondent was retired or did not own/operate augers, resulting in 57 usable questionnaires. Survey responses indicate that the majority of Iowa farmers who participated in this study can correctly identify appropriate shielding for auger intake that meet or exceed ASAE standards. Survey responses suggest that it is common practice in Iowa for youth (age 13 to 19) to operate augers. Iowa farmers in this study perceive the most important contributing factors to auger-related injuries to be operating an auger without shielding, failure to pay attention on the job, moving augers in a raised position, and using hand or feet to redirect the flow of grain. Survey results also indicate that carelessness is perceived to be the leading cause of auger-related injuries, and that auger related injuries can be avoided by having respect for the equipment, being careful, and using common sense. The results also show that the Iowa farmers who participated in this study commonly perform auger-related practices (e.g., moving an auger in a raised position) that they identify as being unsafe.

INSTRUMENT REQUIREMENTS AND METHODS FOR MEASURING VACUUM IN MILKING MACHINES

The instrument specifications given in current international (ISO) and national (ASAE) standards state thatmeasured values should be within 90% of the true amplitude of vacuum change at the various locations in the milking machine.Recommendations are given for the minimum sampling rate and response rate of instruments used to measure vacuum changesfor dry, wet, milkingtime, and cleaningtime tests. These minimum performance requirements should ensure that themeasurement accuracy stated in the ISO and ASAE standards are met.A simple method was developed to measure the response rate of a vacuum recording system. The method can be used, quicklyand easily, by field or laboratory technicians to specify the response rate of their vacuum recording systems. The predominanteffects on response rate of vacuum recording systems are caused by the fittings connecting the electronic vacuum recorderto the measurement point. A major source of measurement error was water or milk in connecting tubes and fittings.Dry and wet tests in the milkline and receiver confirmed previous studies showing that the rate of vacuum change during drytests or in dry parts of the milking machine are much lower than those in wet parts of the machine. The fastest vacuum changeswere measured in the short milk tube and mouthpiece chamber during a liner slip in a milkingtime test. Measurements madein the short milk tube during wet tests corresponded well with those made during wet tests at the teatend of the ISO standardudder.