The International Harvester 15 Series Combines were launched in 1968.

When International Harvester introduced the 15 series combines in 1968 the company had been building self-propelled combines for 26 years and had over a half century of experience in the combine business.  The 15 series were the most luxurious combines from IH to date.  The series included the 315, 615, 715, 815 and 915. The combines had space age features inside roomy air-conditioned cabs equipped with an electronic digital monitoring system and gauges and controls were positioned for easy operation. In the decade of the 1970's IH combines grew up. IH introduced its "Big Mouth" combines with 48 inch wide cylinders on the the 815 and 815 combines. The 915 was IH's largest combine to date offering the power and capacity to handle an 8 row corn head. IH was also ready to meet the smaller operators needs in the 1970's with a range of combines that shared IH big combine features in a smaller package.

 

The IH 315 was the a new multi-crop combine with hydrostatic drive.  It was long on power and capacity with a 72 hp engine, 42 inch wide separator and 70 bushel dual grain tanks.  IH 315 combines could be matched with 10 1/2, 13 or 14 foot grain platforms and 2 row wide or 3 row wide or narrow corn heads.  Cabs were optional.  Rice special 315 models were available.

IH 315 Combine

IH 615 Combine

Offered from 1968 to 1975 the 615 combine was available in conventional belt-drive or hydrostatic drive. Many of IH's proven combine features were standard on the 615.  One of the biggest new features found on the 615 was the all new Quick-Attach grain and corn heads.  A new variable speed cylinder and fan was added to the 615 to improve the combines threshing quality. The 80hp 615 was available with an IH C-263 gasoline engine or a diesel IH D-282 engine. IH 615 combines were built to handle 10, 13, 15 ft grain heads and 2 and 3 row corn heads with settings from 28 to 40 inches. The 615 came from the factory with an 83 bushel grain bin. 

IH 715 Combine

In 1971 International introduced the 715 combine. It can be considered a 615 combine plus.  The 715 shared many features with the smaller 615 and offered several upgrades including larger grain handling capacity with standard 96 bushel grain bin and more horse power with an IH C-301 gasoline engine rated at 107 hp or a the 95 hp IH D-301 diesel engine.  The 715 was equipped to handle grain heads from 10 to 20ft and several variations of 2, 3 and 4 row corn heads with 28 to 40 inch settings.

IH 815 Combine

The International Harvester 815 combine was announced in 1968. Eight grain headers were available for the 815, ranging from 10 to 24 ft. In addition, corn heads could be purchased in 4 and 5 row sizes. IH offered both gasoline and diesel engines including the V-304 or V-345, V-8 gasoline styles and the D-407 or D-414, six-cylinder diesel engines. The 815 and 915 combines were the first IH combine to offer a turret hydro swing auger. This new auger allowed the operator to position the grain spout hydraulically where he needed it while unloading to distribute truck loads evenly.  The unloading spout was 11 ft high and made clearing even the largest trucks and wagons easy.

IH 915 Combine

Monitor control was first introduced on the big 915 combine in 1968.  This feature provided a reliable means of monitoring combine functions.  The 915 was a big step up in combine capacity for IH with a 150 hp DT414 engine and a standard 146 bushel grain bin. The 915 was the first combine from IH that could handle an 8 row head. Unloading all 146 bushels was not a problem on the 915. The 12 inch turret hydro swing auger standard on the 915 and 815 combines could crank grain out of the bin at 1.9 bushels per second. In less than 80 seconds a farmer could have the truck full and be back in the field harvesting.

IH 915 Combine Rice Combine and Edible Bean Combine

The 15 series rice combines were well suited for big rice operations. The IH 915 rice combine offered a 116 bushel bin, the 815 rice 106 bushels and the 715 rice 65 bushels.  The rice combines included the standard equipment found on the corn and grain IH combines with extras such as a spike tooth cylinder and concave in place of a rasp bar, raised leveling auger, feed conveyor divider sheet, special mud shields and an adjustable guide wheel axle.  The 15 series models listed above were also offered as an edible bean combines. The edible bean combines offered a bucket type grain elevator, special slow/high speed variable cylinder drive, stone retarder, perforated screens and a raised leveling auger on the 116 bushel 915 to prevent scuffing.

IH 453 Hillside Combine 

From 1970 to 1978 International offered the 453 Hillside Combine. The 453 was the predecessor of the 403 Hillside. The Hillside Combine was the one IH combine that did not receive 15 series upgrades and styling. It would not be  until 1980 that IH would offer a large modern hillside combine. The 453 was an efficient way to harvest grain in rough sloping terrain. IH offered the only 4-way leveling combine on the market. Not only did the 453 level on sidehills but it also leveled up and down hill as well.  Because the 453 leveled fore and aft as well as side to side, grain would not spill out or bunch up in the grain pan.  The 453 was available with both diesel and gasoline engines rated at 122 hp. Its 80 bushel grain bin could handle input from a 16 1/2 and 18 1/2 ft grain heads.

IH went big in the 1970's  with the15 series. The Axial-Flow combine would be the biggest innovation in IH combines in the late 70's.

Follow the IH Axial-Flow Combine Story on Part IV

Precision Agriculture: Global Positioning System      GPS

Donald Pfost and William Casady, Extension Agricultural Engineers
Kent Shannon, Associate Director of the Missouri Precision Agriculture Center
University of Missouri-Columbia

Note: Mention of companies does not imply recommendation or endorsement by the University of Missouri over other companies not mentioned.

GPS technology

Global Positioning System (GPS) receivers provide a method for determining location anywhere on the earth. Accurate, automated position tracking with GPS receivers allows farmers and agricultural service providers to automatically record data and apply variable rates of inputs to smaller areas within larger fields.

 A GPS receiver can be compared with a simple AM or FM radio. A GPS receiver "listens" for the signals that are broadcast from the satellites of the United States Department of Defense (DOD) Global Positioning System. Orbiting around the earth at an altitude of 12,550 miles, these satellites are in predictable locations; hence, we refer to the system of satellites as the GPS constellation.

 Each satellite broadcasts almanac information containing the position of all satellites in the constellation. GPS receivers use the almanac to determine the position of the satellites. Minor variations in the orbits of the satellites occur due to gravitational forces from the sun and the moon. The DOD continuously monitors the satellites and adjusts the almanac information to represent the actual orbits of the satellites.

 The broadcast signals also contain a precisely timed predictable code that a GPS receiver can use to determine how long the signal required to reach the receiver. A microprocessor within a GPS receiver uses these delays and the position of the satellite to calculate the distance to each satellite, and then uses this information to determine location through triangulation.

 Triangulation is a mathematical method for locating points on a plane in three-dimensional space. If the distances to each of three satellites and your approximate location on the earth are known, the GPS receiver can calculate its terrestrial position. If information from four satellites is available, elevation can also be determined.
 
 

Range determination factors

Each GPS satellite continuously broadcasts two radio signals on separate L-band frequencies (the L-band is from 1,000 to 2,000 MHz). The L1 signal (transmitted at 1575.42 MHz) carries two codes, a Coarse/Acquisition (C/A) code and a Precision (P) code. The L2 signal (transmitted at 1227.60 MHz) carries only the P code, which is encrypted so only the military and other "authorized" receivers can interpret it. The use of both the L1 and L2 signals and their P codes produces what is called the Precise Positioning Service (PPS) and is available to the U.S. and allied military, U.S. government agencies and authorized civilian users. The system available for all civilian use accesses only the L1 signal and the C/A code and is known as the Standard Positioning Service.
 
 

Accuracy

The accuracy obtained generally depends on five factors: 1) proper installation, 2) the degree of technology used in the receiver, 3) the number and location of satellites, 4) errors introduced by selective availability (SA), atmospheric conditions, the troposphere, the ionosphere, and multipathing - radio signals bouncing off objects in the area, and 5) differential corrections.
 
 

Installation

GPS antennas should be mounted on the centerline of a combine, tractor or truck and above any part of the machinery that might obstruct a line of sight to a satellite. If the cab is centered and the top of the cab is above other portions of the machine, a cab-top mounting may be the best location. However, on a steep side slope, a high mounting point will result in an error in position calculation due to the offset in horizontal position.

 GPS and DGPS receivers may have separate antennas but usually there will be a combination antenna so that both are centered at the same location.

 A delay of several seconds often occurs in agricultural applications such as yield monitoring, spraying and fertilizer application.

Example: If the antenna on a sprayer traveling 10 mph is mounted 30 ft ahead of the booms and a rate change at the controller is effected at the boom two seconds later, the rate change will occur when the booms reach the location of the antenna where the change was made. At any other ground speed, the rate change at the booms will not occur at the same location as the controller. A time adjustment must usually be factored into the system to compensate for time delays in sensing or product application.

 Electrical interference can result from electrical storms, power lines, 2-way radios, nearby radio transmitters, electric motors, microwave towers, cellular phones, vehicular electrical equipment such as alternators and ignition systems on spark-ignition engines, and other sources. Changing the position of the antenna or adding noise suppression kits may reduce interference problems from alternators and ignition systems. Follow the instructions for installation of the GPS equipment, making sure that all connections are tight.
 
 

Technology

Low-cost receivers receive signals from one satellite at a time and require more time to determine the location than a receiver capable of receiving four signals simultaneously. Usually, seven to 10 satellites are in view at any one time and more sophisticated receivers will produce the most accurate location.

Reacquisition time is the time it takes to get an accurate position fix after a short-time loss of satellite signals; this may occur for a variety of reasons, including traveling near trees or buildings and losing the 'line of sight' to satellites. Reacquisition time is important for most agricultural applications and, especially, for guidance with applicators and aircraft. New technology in GPS receivers has shortened reacquisition time. Receivers that can track 8-12 satellites are less susceptible to acquisition loss.
 
 

Satellite constellations

Using triangulation to calculate position, small errors in distance can cause large errors in position. The error in calculating position through triangulation increases when the satellites are close together. The best accuracy is produced when the receiver can pick up signals from many widely dispersed satellites (Figure 1).
 
 

Selective availability and other errors

To prevent an enemy from using GPS satellite signalsfor determining locations on earth, the DOD "scrambles" the signals sufficiently to introduce an error of about 100 meters in an uncorrected location calculation. The term for this is "selective availability" (SA). Atmospheric, tropospheric and ionospheric conditions, however, also cause distortions or errors in calculating distance; natural errors due to these conditions are not easily or reliably predicted. Hence, even in the absence of SA, differential corrections will still be required to accurately calculate position.

 Multipathing, the phenomenon that creates distorted television signals is caused by signals that bounce off of other objects before reaching the antenna (Figure 2). Multipathing cannot be corrected by differential corrections.
 
 

Differential corrections

Stationary GPS receivers are used to calculate the total error due to SA, variable atmospheric conditions and other factors. The concept is simple. A stationary receiver always has a known location; because the actual positions of the satellite and the receiver are known, the true range (distance) is known. The distance calculated by the receiver using the broadcast signals is known as the pseudorange, which is generally in error due to the combined sources of all errors. The difference between the true range and the pseudorange is the error and is known as the differential correction (Figure 3).
 
 

Differential correction data can be purchased and used at a later time in a process known as post processing to correct the errors in recorded data. However, the most common approach is to connect a differential corrections receiver to a GPS receiver to provide real-time corrections (Figure 4).
 
 

Many units incorporate GPS receivers and differential corrections receivers into the same unit. These are often referred to as differentially-corrected GPS (DGPS) receivers. Differential corrections signals are available from the Coast Guard or Army Corps of Engineers and through commercial sources, which, for a fee, will provide signals from a satellite or a land-based tower. Where these sources aren't available, or for special applications, a private differential corrections source can be installed.

 Some of the newer DGPS receivers combine the capability of receiving differential signals from both the Coast Guard beacons and from a satellite service. Refer to Table 1 for a comparison of features of Coast Guard and satellite-based differential corrections sources.

 Table 1. Comparison of Coast Guard and satellite differential correction sources by feature.

Coast Guard signals

The Coast Guard signals are broadcast in the frequency range of 285-325 kHz (just below the usual AM-radio band) where radio waves travel as ground waves and are not limited to line-of-sight reception like FM-radio stations.

 The signals are series of pulses similar to those of the GPS satellites. Referred to as Minimum Shift Keying modulation, the signal is less sensitive to electrical interference and noise than AM-radios.

Missouri has free access to correction signals from Coast Guard beacons located near St. Louis (@ 322 KHz), Kansas City (@ 305 KHz), Tulsa (@ 299 KHz), Rock Island (@ 311 KHz), Memphis (@ 310 KHz) and Omaha (@298 KHz).

 The range of the Coast Guard beacons is approximately 150 miles in good weather (electrical storms cause interference). Accuracy decreases with distance from the transmitter. This service is expected to become the choice of many agricultural users, especially in Missouri where several signals are available.

 A disadvantage of the Coast Guard differential corrections signal is the rate at which the beacon transmits or repeats messages. Most Coast Guard sites broadcast at 200 bits per second. At this broadcast rate, the age of a satellite's differential correction can be as old as four seconds. For some applications, such as guidance, this update rate may be unacceptable. For guidance applications, update rates of two to ten times per second may be required.

 Typical Coast Guard beacon receivers have two channels. One channel receives the differential correction and the other is searching for the best incoming signal. This helps to ensure against loss of a DGPS signal if at least two beacons are within range.
 
 

Satellite-based correction signals

For the user, one of the simplest types of differential corrections signals is transmitted from a geostationary satellite. Companies such as Omnistar, Accqpoint and Racal provide this service.

 The typical annual user's fee ranges from $500 to $800. The correction signal is available throughout most of North America. The accuracy of high quality receivers is generally considered to range from one to three meters RMS. Interference from man-made sources is minimal.

 Satellite-based signals may have an advantage for operation around trees and buildings since the satellite is nearly overhead at most locations and within the DGPS receiver's line-of-sight.
 
 

Land-based correction signals

Several commercial land-based correction signal services are also available for a fee. Some companies put up their own transmitters to broadcast correction signals; these include SatLoc, Mobile Data and CSI.

 Some commercial service providers piggyback correction signals onto commercial FM radio station transmitters. These sub-carriers include Pinpoint Communications, DCI and others.
 
 

Private GPS receiver and radio transmitter

GPS users not covered by Coast Guard or commercial sources of differential corrections can install a stationary receiver and transmitter to provide their own differential corrections source. Few users in Missouri will choose to buy and install their own fixed GPS receiver and transmitter since the Midwest has other choices available.
 
 

Cost vs. accuracy

The accuracy attainable with GPS depends partly on how much you are willing to spend, ranging from approximately $100 to $100,000. A low-cost (from $100 to $500) GPS receiver without DGPS capability may be sufficiently accurate for some crop scouting applications, for navigating highways or for locating your favorite fishing spot on a lake. The RMS horizontal accuracy may be about 50 yards.

 The cost for a basic DGPS receiver suitable for most agricultural applications is about $3,000 to $5,000 and provides RMS accuracy of at least three meters with a typical accuracy of one meter, which is sufficient for yield monitoring and grid soil sampling.

 If you need a GPS receiver for guidance (for spraying, fertilizer application, etc.), the cost may be up to $25,000. Such systems provide accuracy down to a few inches. Since sprayers and fertilizer spreaders can travel fairly quickly, lower quality GPS equipment may not update position quickly enough to be used for guidance or control, although GPS systems with high update rates and accuracies in the range of one foot or less are becoming available at lower prices.

 The annual subscription cost for some differential correction services varies with the level of service (accuracy). Some providers offer three levels of service, e.g., one provider has a premium service for better than 1 meter accuracy, intermediate service for accuracies in the range of 5 meters and a basic service for accuracies in the range of 10 meters. Typical approximate costs may be $600, $250 and $75 per year, respectively, depending on the level of service.
 
 

Accuracy of GPS units

Accuracy of GPS units may be stated in a variety of statistical terms, which one is used may not be specified. Most statistical definitions of GPS accuracy assume that position errors are random in nature and follow a normal distribution. One measure of accuracy is the Circular Error Probable (CEP). This term applies to horizontal position estimates. A CEP of 1 meter is interpreted to mean that 50 percent of the position estimates will be within 1 meter of the actual position; the other 50 percent can be anywhere in the universe.

 Two frequently used accuracy terms are the RMS (also known as one sigma) and 2DRMS (also known as two sigma). The acronym RMS stands for root mean square and is approximately equal to the standard deviation (SD). If the calculated positions were normally distributed about the true position, then 68 percent of the computed positions would be within +/- one standard deviation and 95 percent would be within +/- two SD's of the true position (2DRMS).

 When comparing the accuracy of GPS units, make sure that the accuracies are specified in the same terms (CEP, RMS or 2 DRMS).
 
 

Coordinate systems

Several coordinate systems are in use for mapping and may cause problems with compatibility between software systems. Users frequently need to transform position data into a plane (flat) coordinate system, either to merge them with another data set, to plot a map of the GPS results, or to perform further calculations for such parameters as area, distance or direction (plane coordinate systems are usually easier to work with than geodetic coordinates). When using data and maps from several sources, coordinates must be based on the same datum. The coordinate system differences, which are caused by a different reference frame, ellipsoid and data adjustment, are significant (up to several hundred meters) and cannot be ignored.

 Several commercially-available software programs produced by well-known GIS vendors treat the coordinate shifts incorrectly. The National Geodetic Survey provides software (LEFTI and NADCON) at a nominal charge to compute datum shifts. Boundary coordinates on older paper copies of soil maps should be converted to the preferred datum (probably WGS84) before they are digitized.

GPS receivers can usually report position information in more than one format. The most common format is lat/lon (latitude and longitude). Lat/lon coordinates are recorded in angular units of degrees, minutes and seconds. One second of latitude is equal to about 30 meters. GPS receivers may display lat/lon in degrees plus minutes to four decimal places (instead of minutes and seconds). Most geographic information system (GIS) software is capable of using more than one format and may automatically convert lat/lon coordinates to a coordinate system such as Universal Transverse Mercator (UTM) or State Plane Coordinates (SPC) to calculate distances in meters or feet.

UTM and SPC systems project portions of the earth's curved surface onto a flat map and report locations as actual distances from a reference point in meters and feet, respectively. Hence, no conversions are necessary to calculate distance or area.

 Commercial software available from several GPS vendors will compute UTM or state plane coordinates from GPS data. These coordinates are usually based on the WGS-84 datum and thus are in the NAD-83 system. If these must be transformed to NAD-27, it is advisable to do the NAD-83 to NAD-27 transformation in geodetic coordinates, and then make the conversion to plane coordinates as the final step.
 
 

Universal Transverse Mercator Coordinates

The UTM coordinate system is a worldwide system originally adopted by the U.S. military in 1947, and since has been widely used by civilian mapping in many countries. The UTM system is consistent throughout the world and one set of equations will allow calculation of coordinates at any location. The world is divided into 60 zones each spanning 6 degrees in longitude and extending north and south from a latitude of south 84 degrees to north 84 degrees.

State plane coordinate system

In the 1930s, the U.S. Coast and Geodetic Survey established a plane coordinate system for each of the 48 states. One to five zones were established in each state with a Lambert Conformal or a Traverse Mercator projection. The specific projection and the size of the zone was selected to fit the geometry of the state and to keep distortions at or below one part in 10,000.
 
 

Summary

Together, the Global Positioning System and GPS receivers provide the means for determining position anywhere on the earth. Developed by the U.S. DOD and used for many purposes, GPS has also made precision farming a reality. A typical configuration for on-farm agricultural applications includes a GPS receiver and antenna, a differential corrections receiver and antenna, and cables to interface differentially-corrected GPS data from the receiver to other electronic equipment such as a yield monitor or a variable rate controller.

 GPS can provide accurate position data when installed and operated properly, but can produce false readings under poor conditions. Use similar statistical measures for comparing the performance characteristics of various receivers. Few, if any, receivers will provide accurate position estimates 100 percent of the time. Even in the absence of intentional dithering of signals known as selective availability (SA), differential corrections receivers are necessary to account for other sources of error to provide the accuracy required for precision farming.
 
 

Glossary

Anywhere fix: The ability of a receiver to start position calculations without being given an approximate location and approximate time.

 Bandwidth: The range of frequencies in a signal.

 C/A code: The standard (Coarse/Acquisition) GPS code. A sequence of 1023 pseudo-random, binary, biphase modulations on the GPS carrier at a chip rate of 1.023 Mhz. Also known as the "civilian code".

 Carrier: A signal that can be varied from a known reference by modulation.

 Carrier frequency: The frequency of the unmodulated fundamental output of a radio transmitter.

 Carrier phase GPS: GPS measurements based on the L1 or L2 carrier signal.

 Channel: A channel of a GPS receiver consisting of the circuitry necessary to receive the signal from single GPS satellite.

 Clock bias: The difference between the clock's indicated time and true universal time.

 Code phase GPS: GPS measurements based on the pseudo-random code (C/A or P) as opposed to the carrier of that code.

 Control segment: A world-wide network of GPS monitor and control stations that ensure the accuracy of satellite positions and their clocks.

 Differential positioning: Accurate measurement of the relative positions of two receivers tracking the same GPS signals.

 Dilution of precision: The multiplicative factor that modifies ranging error. It is caused solely by the geometry between the user and his set of satellites. Known as DOP or GDOP.

 Dithering: The introduction of digital noise. This is the process the DOD uses to add inaccuracy to GPS signals to induce Selective Availability.

 Ephemeris: The predictions of current satellite position that are transmitted to the user in the data message.

 Geometric Dilution of Precision (GDOP): See Dilution of Precision.

 Ionosphere: The band of charged particles 80 to 120 miles above the earth's surface.

Ionospheric refraction: The change in the propagation speed of a signal as it passes through the ionosphere.

 L-band: The group of radio frequencies extending from 1000 MHz to 2000 MHz. The GPS carrier frequencies (1227.6 MHz and 1575.42 MHz) are in the L band.

 Meter: a metric measure of length equal to 3.28 feet.

 Multipath error: Errors caused by the interference of a signal that has reached the receiver antenna by two or more different paths. Usually caused by one path being bounced or reflected.

 Multi-channel receiver: A GPS receiver that can simultaneously track more than one satellite signal.

 Multiplexing channel: A channel of a GPS receiver that can be sequenced through a number of satellite signals.

 P-code: The Precise code. A very long sequence of pseudo-random binary, biphase modulations on the GPS carrier at a chip rate of 10.23 MHz which repeats about every 267 days. Each one-week segment of this code is unique to one GPS satellite and is reset each week.

 Precise Positioning Service (PPS): The most accurate dynamic positioning possible with standard GPS, based on the dual frequency P-code and no SA.

 Pseudo random code: A signal with random noise-like properties. It is a very complicated but repeating pattern of 1's and 0's.

 Pseudorange: A distance measurement based on the correlation of a satellite transmitted code and the local receiver's reference code, that has not been corrected for errors in synchronization between the transmitter's clock and the receiver's clock.

 Satellite constellation: The arrangement in space of a set of satellites.

 Selective Availability (SA): A policy adopted by the Department of Defense to introduce some intentional clock noise into the GPS satellite signals thereby degrading their accuracy for civilian users.

 Standard Positioning Service (SPS): The normal civilian positioning accuracy obtained by using the single frequency C/A code.

 Static positioning: Location determination when the receiver's antenna is presumed to be stationary on the earth. This allows the use of various averaging techniques that improve accuracy by factors of over 1,000.
 
 

References

GPS: A Guide to the Next Utility. 1993. Trimble Navigation Ltd., P.O. Box 3642, Sunnyvale, CA 94088-3642.

 Differential GPS Explained. 1996. Trimble Navigation Ltd., P.O. Box 3642, Sunnyvale, CA 94088-3642.

 The Precision-Farming Guide for Agriculturalists. 1997. John Deere Publishing , Dept. 374, John Deere Road, Moline, IL 61265-8098. Phone 1-800-522-7448.

 The State of Site-Specific Management or Agriculture. 1997. Published by: the American Society of Agronomy, Inc.; the Crop Science Society of American, Inc.; and the Soil Science Society of American, Inc.

 Target Farming: A Practical Guide to Precision Farming Concepts and Technology. 1996. Written and published by Ron Johnson, A.Sc.T., 511 Haslam Cres., Saskatoon, Sask S7S 1E7 Canada, Phone and Fax: 306-665-1610

Agricultural Landowners' Lack of Preference for Internet Extension

Jennifer L. Howell
Pierce Cedar Creek Institute
Hastings, Minnesota
howellj@cedarcreekinstitute.org

Geoffrey B. Habron
Department of Fisheries and Wildlife
Department of Sociology
Michigan State University
East Lansing, Michigan
habrong@msu.edu

Background

Given the increase in Internet use among many different segments of U.S. society (U.S. Department of Commerce 2002), Extension professionals and agricultural educators express an increasing desire to inform farmers about improved management practices and other issues via the Internet (Hall, Dunkelberger, Ferreira, Prevatt, & Martin, 2003; O'Neill, 1999). In the 1990s, research indicated limited experience and perception of the Internet for educational communication purposes.

For example, a 3-year longitudinal study determined that while the percentage of respondents who used the Web to gain Extension-related information increased from 1.4% to 10%, the vast majority of respondents did not rely on that information source (Suvedi, Campo, & Lapinski, 1999). Farmers rated Internet-delivered instructional technologies much lower than traditional instructional techniques (Trede & Whitaker, 1998). Gloy, Akridge, & Whipker, (2002, p.18) suggests that, "At this point, it appears that the Internet might be a compliment rather than a substitute for traditional information sources."

Recent trends suggest that the Internet may now provide a more useful communication strategy. In 2001 an estimated 54% of U.S. population utilized the Internet, with children and teen-agers comprising the most frequent users (U.S. Department of Commerce 2002).

Rural Internet use grew 24% annually between 1998-2001, equalizing the level of urban use at 53% (U.S. Department of Commerce 2002). However, rural users often lack choices of service providers (Malecki, 2003) and access to high-speed connections (Malecki, 2003; U.S. Department of Commerce, 2002).

Between 1998-2001, Internet use increased 25% annually for homes with less than $15,000 annual income (U.S. Department of Commerce 2002), suggesting that even limited income homeowners continue to overcome such economic constraints. Farmers who utilize precision agriculture and other technologically driven production strategies may not view the Internet as a hurdle, but may view the Internet as the best way to obtain cutting-edge information (Ferguson, 2002). Therefore, evidence suggests that Extension needs to continue to embrace the use of the Internet (Hall et al., 2003; O'Neill, 1999; Tennessen, PonTell, Romine, & Motheral, 1997).

Methods

In order to obtain information about the role of communication preferences of Michigan's agricultural landowners with respect to watershed conservation, a random sample of residents from four agricultural watersheds was asked to complete a survey instrument titled "A Survey of Landowner Watershed Information Needs." In the Spring of 2001, 922 survey instruments were mailed to landowners in four agricultural watersheds within the state of Michigan: the Lake Macatawa, the Gun River, the North Branch Flint River, and the Upper Thornapple.

Watersheds were chosen based on level of watershed conservation activity and existing Extension contacts. The Lake Macatawa and Gun River included Total Maximum Daily Load (TMDL) and Clean Water Act Section 319 planning and implementation activities. Both watersheds also included Extension staff who participated actively in watershed activities. In contrast, few watershed conservation activities occurred in the Upper Thornapple and North Branch North Branch Flint River watersheds.

The design enables longitudinal comparison where more changes in landowner attitude and behavior are expected in active watersheds than less active watersheds. Names and addresses of landowners were retrieved from county geographic information systems (GIS) or Equalization offices for each of these watersheds.

The survey, including both open- and closed-ended questions, was developed using many question items derived from previous, peer-reviewed and field-tested studies from agricultural communication professionals in order to ensure validity and reliability. Once the survey questions were formulated, the survey instrument was peer reviewed by a number of Extension agents and water quality professionals before it was mailed to agricultural landowners.

In the questionnaire, participants were asked to report demographic information such as age, education level, income, farm operation, farming status, and farm size. Respondents also identified how often they participated in Extension programs and which communication strategies they preferred to learn about watershed conservation issues. In addition, respondents provided information about their Internet access location and how often they use the Internet for management decisions.

Survey methodology followed Dillman's Total Design Method (Salant & Dillman, 1994). The survey instrument was initially mailed to the sample of agricultural landowners in May of 2001. A reminder postcard was sent to the sample population approximately 3 weeks later. About 4 weeks following the second mailing, non-respondents were mailed a second copy of the questionnaire. Respondents completed and returned 403 of the 922 survey instruments, providing an overall response rate of 43.7%.

Survey Data Analysis

Data were analyzed using SPSS 10.0.7 statistical software for social statistics (SPSS, 2000). Statistical analysis consisted of Pearson's correlation (r), Pearson's Chi-square test of independence (X²), and One-way Analysis of Variance (F-test) depending on the nature of the variables tested. Relationships between two ordinal variables were analyzed using Pearson's correlation. Comparisons between means were examined using ANOVA, while differences between proportions were assessed using Pearson's Chi-square test of independence. The homogeneity of variance was then tested using Levene's statistic.

In all cases, Levene's statistic was greater than 0.05, indicating that one would fail to reject the null hypothesis that the variances are equal and that ANOVA could be used. If differences between groups were detected using ANOVA, Bonferroni's Post Hoc test was used to determine which means differed significantly. Bonferroni's Post Hoc test uses a more stringent confidence level for each interval than other multiple comparison procedures, ensuring the overall confidence level is acceptably high.

Non-Response Analysis

Because the study did not obtain a 100% response rate, differences between respondents and non-respondents could threaten external validity. To address representativeness, the research team specifically compared early and late respondents on Likert-type scale items and demographic information. (Lindner, Murphy, & Briers, 2001). Because late respondents tend to be similar to non-respondents (Miller & Smith, 1983; Pace, 1939), demographic data and responses to Likert-type scale questions from early respondents were compared to data from late respondents. If no differences are found, then respondents are said to adequately represent the sample (Miller & Smith, 1983).

Results

Of the 29 variables tested for non-response bias, only 2 came out significant between early and late respondents. Compared to non-respondents, respondents implement higher cover crop use and less frequent manure application on the same field (r=0.245, p=0.005 and r=0.195, p=0.028, respectively).

Overall, the most preferred communication strategies were written methods such as newsletters, printed bulletins, and fact sheets. The least preferred communication strategies were computer and Internet methods such as software, e-mail, and World Wide Web pages (Figure 1).

Of all the communication strategies presented to respondents, 76.6% of respondents preferred written communication strategies such as newsletters, printed bulletins, and fact sheets to learn more about watershed conservation. Most (57%) of the respondents preferred personal, face-to-face communication strategies such as farm meetings, workshops, field days, demonstration tours, visits to resource offices (Extension or conservation district), personal visits to their homes by resource persons, and visits to a university to learn more about watershed conservation. In addition, 39% of respondents preferred media sources such as newspapers, televisions, radios, and video tapes to learn more about watershed conservation, while 18.7% of respondents preferred computer or Internet sources such as software packages, e-mail, and World Wide Web pages to learn more about watershed conservation.

Figure 1.
Survey Respondents' Preference for Traditional or Technological Communication Strategies to Learn About Watershed Conservation Practices

Note: Percentages add up to more than 100% because respondents were asked to indicate all communication strategies that applied.

Watershed Results

Results indicate that watershed residence had no significant effect on agricultural landowners' preference for communication strategies. Overall, respondents from all four watersheds had a higher preference for written materials than all other communication strategies. There is no statistical difference (Table 1) in preference for communication strategies among watersheds (written communication strategies, X²=0.997, p=0.802; personal communication strategies, X²=4.503, p=0.212; media, X²=2.401, p=0.493; and computer/Internet, X²=5.480, p=0.140).

Demographic Explanatory Factors

Age

Table 2 demonstrates the influence of age on communication strategy preference. There is a statistical difference between age groups and preference for written communication strategies, media, and computer or Internet methods of learning about watershed conservation issues. Results specifically indicate that age has a significant effect on respondents' preference for computers and Internet for learning about watershed conservation issues. Younger age groups have a higher preference for computer-based resources than older age groups.

Education Level

Table 3 demonstrates the influence of respondents' education level on respondents' preference for communication strategies to learn about watershed conservation issues. A statistical relationship exists between respondents' levels of education and preference for computers or Internet as communication strategies (r=0.303, p=0.000). As level of education increases, so does respondents' preference for computers and Internet as a communication strategy.

Gross Annual Income Level

Table 4 demonstrates the effect income level has on respondents' preference for communication strategies to learn about watershed conservation issues. There is a statistically significant difference between level of income and respondents' preference for computers and the Internet as communication strategies. Specifically, as respondents' gross annual income level increases, so does their preference for computers and the Internet to learn about watershed conservation issues.

Role of Internet Access

32.2% of respondents did not have Internet access. Of all respondents with Internet access, 47.4% of them had Internet access in their home, 23.2% of respondents had Internet access at their business, 17.5% of respondents had Internet access at a local school or library, and 13.6% of respondents had Internet access at a friend's or relative's home (Figure 2). Regardless of Internet access, the majority of respondents (74.6% of respondents with Internet access and 77.8% of respondents without Internet access) still preferred written materials such as newsletters/mailers and printed bulletins/fact sheets than the other communication strategies.

Figure 2.
Internet Access Locations

* Note: Percentages do not add up to 100% because respondents were requested to indicate all locations where they had Internet access.

However, access to the Internet significantly affects respondents' preference for computers and the Internet. Survey respondents with Internet access expressed a significantly higher preference (27.5%) for computers and the Internet than did landowners without Internet access (1.6%, X²=18.607, p=0.000) (Table 5). In addition, results indicate that the location of Internet access has a significant effect on respondents' preference for the Internet as a communication strategy. A significantly higher percentage of respondents preferring the Internet had Internet access in their homes (X²=16.948, p=0.000), their business (X²=9.502, p=0.002), or at a local library or school (X²=4.813, p=0.028) than did respondents who did not prefer the Internet as a communication strategy.

Discussion

Overall, survey respondents preferred traditional written communication strategies such as newsletters, printed bulletins, and fact sheets. These findings are supported by research conducted by Gloy et al. (2000) that revealed the strong importance of farm publications as communication tools. In addition, respondents expressed the least amount of preference for technological communication strategies such as computers, e-mail, and the Internet. These findings mesh with results by Tavernier, Adeaja, Hartley, and Schilling (1996) that indicate the lack of preference by farmers for modern communication technology.

Despite an overall lack of support for the Internet, it is important to know whether preference for innovative communication strategies is related to farmers' demographic characteristics. Results indicate that respondents' preference for computers and the Internet as communication strategies to learn about watershed conservation issues is related to respondents' age, level of education, and gross annual income level. Younger, more educated farmers demonstrate a greater appreciation for modern sources of information (Hall et al., 2003; Riesenberg & Gor, 1989). The youngest respondents in the current study indicated a significantly higher preference for computers and the Internet than did older respondents.

Because one would expect younger farmers to be more inclined to utilize modern technology (Kolodinsky, Cranwell, & Rowe, 2002; U.S. Department of Commerce, 2002; Tavernier et al., 1996), one could argue that while farmers currently prefer traditional written communication strategies over computers and the Internet to learn about watershed conservation issues, farmers may prefer technological communication strategies in the future. In support of these findings, Suvedi et al. (2000) illustrated that farmers' use of Internet sources in Michigan increased from 1.4% to 10.0% between the years 1996 and 1999.

Results also indicate that level of education is positively correlated to respondents' preference for written materials and computers. According to Gloy et al. (2000), higher levels of education are expected to be positively related to the usefulness of information received from all information sources. In addition, higher levels of education should increase the usefulness of information received from the sources that deliver the most sophisticated information (Gloy et al., 2000).

Results from this study resemble results from other studies (Richardson & Mustian, 1994; Bowen & Escolme, 1990). According to Richardson and Mustian (1994), college graduates were found to have a significantly higher preference for method demonstration and videotapes than did persons who have less than a college education. Bowen and Escolme (1990) discovered that three-fourths of farmers who used computers had at least some college education.

Additionally, gross annual income levels are positively correlated with respondents' preference for computers and the Internet. These results are consistent with previous research (Tavernier et al., 1996) where farmers with high gross annual incomes (more than $100,000/year) increasingly adopted computer technology. Further, those who adopt high technology precision agriculture are also more likely to utilize Internet communication (Ferguson, 2002). This derives in part from the suggestion that more profitable farmers have a greater capacity to purchase the newest and most expensive technology (Tavernier et al., 1996).

Not only are farmers' preferences for computers and Internet related to demographics such as income and education level; farmers have also been reluctant to adopt computers and innovative technologies due to lack of convenient Internet access (Hall et al., 2003; Samson, 1998; Tavernier et al., 1996; Iddings & Apps, 1992). Regardless of whether respondents had Internet access, the majority of respondents still preferred written materials to the Internet to learn about watershed conservation issues. These results suggest that even if agricultural landowners have Internet access, they will likely still express a higher preference for more traditional or written communication strategies. However, having access to the Internet at home or work does significantly increase one's preference for the Internet as a communication strategy.

Extension Implications

Based on previous direct experience research such as the Technology Acceptance Model (TAM) and user acceptance studies focusing on individual differences (Irani, 2000), subjects with greater prior experience with a technology will more likely use it than those who lack experience (Figure 3). Previous research indicates that Internet experience and perceived usefulness were the strongest predictors of behavioral intent to use Internet communication tools (Irani, 2000). Therefore, understanding the factors that influence attitude and user perceptions toward technology is a critical need (Irani, 2000). The Technology Acceptance Model states that increased perceptions of ease of use and technology usefulness lead to increased use (Figure 3).

Figure 3.

The Technology Acceptance Model (Hubona & Geitz, 1999)

If information technology and telecommunications are to satisfy the informational needs and extend the capabilities of the farmer, both the technology and the dissemination strategy must be sufficiently flexible to adapt themselves to the farmers' way of working (Wilde & Swatman, 1996). Extension should organize seminars, institutes, and workshops to train farmers in computer applications for agriculture (Bamka, 2000; O'Neill, 1999; Findlay, Zabawa, Morris, & Oben, 1993). For example, incorporating youth to work with senior citizens significantly improved the seniors' perceptions of their comfort and skill levels regarding Internet use up to six months after training (Kolodinsky et al., 2002).

However, a need exists to determine the actual effectiveness of Web sites both with and without training sessions to help guide participants through the program. Technical training (Bamka, 2000; O'Neill, 1999) and application to real needs emerge as crucial aspects to reach beyond the innovators and early adopters (Hall et al., 2003; Ferguson, 2002; Carr, 1999).

If farmers perceive technology as difficult to learn, too time consuming to use, or in some way presenting a threat, they probably will not use it (Carr, 1999). Therefore, in addition to providing training sessions to introduce farmers to the benefits of using the Internet as a communication strategy, educators must specifically address reasons why farmers are hesitant to utilize the Internet as a communication strategy on an individual needs basis (Hall et al., 2003). This is particularly important if a strong desire exists among specialists to provide data via Web sites because they prove to be more time and cost efficient than newsletters and brochures.

Acknowledgements

The United States Department of Agriculture, Cooperative States Research, Extension and Education Service, National Integrated Water Quality Program provided funding for the research. The Survey Research Center at Michigan State University processed our mail surveys. We appreciate the helpful comments of Murari Suvedi at Michigan State University and three anonymous Journal of Extension reviewers.

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This article is online at http://www.joe.org/joe/2004december/a7.shtml.

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