Journal of Nematology 30(4):431-435. 1998. © The Society of Nematologists 1998.
Precision Farming and Precision Pest Management: The Power of New Crop Production Technologies 1 R. MACK STRICKLAND, DANIEL R. Ess, AND SAMUELD. PARSONS 2 Abstract: The use of new technologies including Geographic Information Systems (GIS), the Global Positioning System (GPS), Variable Rate Technology (VRT), and Remote Sensing (RS) is gaining acceptance in the present high-technology, precision agricultural industry. GIS provides the ability tO link multiple data values for the same geo-referenced location, and provides the user with a graphical visualization of such data. When GIS is coupled with GPS and RS, m a n a g e m e n t decisions can be applied in a more precise "micro-managed" m a n n e r by using VRT techniques. Such technology holds the potential to reduce agricultural crop production costs as well as crop and environmental damage. Key words: agriculture, geographic information systems, GIS, global positioning system, GPS, management, nematode, remote sensing, review, RS, variable rate technology, VRT.
Persons involved with production agriculture today e n c o u n t e r myriad new technologies which generate information that may e n h a n c e m a n a g e m e n t decisions. Such technology generates large amounts of data. The ability to m a n a g e and correctly i n t e r p r e t these data are critical to their use and adoption. In this p a p e r we provide a basic description o f the technologies available for p r o d u c t i o n agriculture in the categories of the Global Positioning System (GPS), Geographic Information Systems (GIS), Remote Sensing (RS), Variable Rate T e c h n o l o g y (VRT), and Precision Farming (PF). GLOBAL P O S I T I O N I N G SYSTEM
The Global Positioning System (GPS) is a network of satellites, controlled by the U.S. D e p a r t m e n t of Defense, designed to help ground-based units d e t e r m i n e their realtime location using latitude and longitude coordinates. For agricultural applications, GPS is being used for machine guidance a n d c o n t r o l (variable-rate-input applications, described later) and data collection during harvesting operations, soil sampling, and field scouting (Morgan and Ess, 1997). The GPS consists o f three segments. T h e
Received for publication 14 October 1997. 1 From the syanposium "Nernatology in the Information Age" presented at the Annual Meeting of the Society of Nematologists, 19-23 July 1997, Tucson, AZ. 2 Professor, Assistant Professor, and Professor, Agricultural and Biological Engineering Department, 1146 Agriculture and Biological Engineering Building, Purdue University, West Lafayette, IN 47907-1146. Contact author: R. Mack Strickland. E-mail:
[email protected]
first is composed o f 24 satellites (21 operational, 3 spares) orbiting 20,200 km above the Earth and providing line-of-sight signals and 24-hour coverage. T h e satellites travel in one of six orbital planes and make complete orbits in slightly less than 12 hours. Each satellite transmits a Pseudo R a n d o m Noise (PRN) code that tells precisely where it was when it sent the signal and the precise time the signal was sent. T h e second segm e n t of the system consists of ground-based control centers that calculate the orbit of each satellite a week or so into the future, p r e d i c t i o n o s p h e r i c conditions over that time, and upload the data to each satellite's computer. By consulting its clock and the e p h e m e r i s , the satellite d e t e r m i n e s a n d transmits its l o c a t i o n continuously. T h e third segment of the GPS is a signal receiver that typically sees three to eight satellites at any instant, determines their positions, then calculates distances to the receiver based on the time difference between signal transmission and reception. T h e receiver requires a m i n i m u m o f 3 satellites for two-dimensional (latitude and longitude) positioning and 4 for three-dimensional (latitude, longitude, and altitude) positioning. T h e a n t e n n a for a GPS receiver needs a clear line of sight. Any field obstruction that can block sunlight (trees, buildings, steep slopes, etc.) can also block a GPS signal (Lange, 1996). Equipped with a GPS receiver, an observer can navigate or collect positional information while stationary or moving. Sources of error in a GPS position estimate may include one or m o r e o f the fop 431
432 Journal of Nanatology, Volume 30, No. 4, December 1998 lowing factors: (i) atmospheric-ionospheric effects that may delay radio transmissions; (ii) multi-path e r r o r due to signal reflections from nearby objects; (iii) ephemeris, defined as orbital position in relation to time; and (iv) Selective Availability ( S / A ) - - a D e p a r t m e n t o f Defense-induced clock shift. For most applications in agriculture it is necessary to correct for S/A and o t h e r error factors to reduce the position e r r o r from 100 m or m o r e to somewhere in the 1-to-5-m range. Differential GPS (DGPS) accomplishes this task by using two or m o r e GPS receivers working together simultaneously. O n e reference receiver is located at a precisely known location (base station) and computes a continuous stream of position data. Differences between the actual and c o m p u t e d position can be d e t e r m i n e d to p r o d u c e a corrected data set (the differential correction). The second receiver (mobile unit) is used to compute position data in the field. Most of the error in the position estimation of the mobile unit can be removed by applying the differential correction transmitted to it from the base station because the two receivers will experience essentially identical errors for any given mom e n t in time. A mobile DGPS unit must have two r e c e i v e r s - - o n e for GPS signals, one for differential correction data. I t is possible for end users to set up, operate, and maintain their own differential correction base station. However, because o f the high initial cost, most choose to use one of three services currently available. Systems that utilize U.S. Coast Guard (USCG) Beacon correction signals cost $1,500 to $5,000, with no annual fee. Characteristics of this system include: free correction signal, lowerf r e q u e n c y signals that travel outward as g r o u n d waves to a 320-kin (200-mile) radius, the digital frequency-modulated (FM) signal that is less sensitive to noise than AM radio, service areas near coastal and inland waterways, a n d signal o u t a g e s c o n t r o l l e d by USCG. A second service option is subscription to an FM sub-carrier. Such systems cost $1,500 to $3,500, with a $75 to $900 annual fee. Characteristics of FM sub-carrier systems include: a correction signal that must be
p u r c h a s e d , h i g h e r - f r e q u e n c y signals that travel as space waves to an 80-km (50-mile) radius, the FM-band signals that are less susceptible to atmospheric interference, and signal outages controlled by the local FM station. T h e third option is a satellite-based system, with a cost o f $3,000 to $7,000 and an annual fee o f $600 to $1,500. Satellitebased system characteristics include: a correction signal that must be purchased; widearea coverage, including the c o n t i n e n t a l United States, Mexico, and m u c h o f Canada, that is not affected by obstructions as are radio links; and signal outages controlled by the satellite operator. GEOGRAPHIC INFORMATIONSYSTEM
A Geographic Information System (GIS) is a collection of c o m p u t e r hardware, software, and procedures designed to support the compilation, storage, retrieval, analysis, and display of spatially referenced data that can assist planning and m a n a g e m e n t decisions (Aronoff, 1989). A GIS for crop production might include i n f o r m a t i o n f r o m various sources pertaining to field history, input operations, GPS-based yield maps and soil surveys, aerial p h o t o g r a p h y , satellite imagery, a n d pest or p a t h o g e n scouting data. The data are shown spatially (geo-referenced) on top of a base map of the field, allowing layers to be c o m b i n e d to provide accurate analysis of crop health and maturity. Once the base map is in place, the farm manager can collect and input data (e.g., weather, insect and weed problems, nematode densities, seed varieties, and planting populations) to provide information about the current crop, assess treatments, and potentially generate projected harvest maps. All GIS packages have a user interface, database management-creation-data entry capabilities, spatial data manipulation, analysis tools, and display-product generation functions. A GIS can integrate geo-referenced data and p e r f o r m complex spatial queries and analyses of spatial features with attribute data (seed cultivar, population rate, etc.). A system has topological capabilities and can define the locations o f data elements in
Precision Farming Technology: Strickland et al. 433 space with respect to one a n o t h e r but without reference to actual distances. A GIS also can be used to relate new geographical information by integrating data layers to show the original data in different ways and from different perspectives. A GIS can combine both vector and raster data and related attributes, which greatly expands its power and utility. It is important that e n d users understand any limitations associated with GIS data before incorporation into a m a n a g e m e n t plan. Some factors to consider are: (i) m e t h o d o f data collection, (ii) accuracy of the data, (iii) i n t e n d e d p u r p o s e o f the data, (iv) meaning of the attributes, and (v) the person who collected or compiled the data. With the i m p l e m e n t a t i o n o f GIS-related technologies, it is anticipated that e n d users should be able to improve yields, lower production costs, improve the quality o f the crop, and more accurately forecast yields. REMOTE SENSING
Remote Sensing (RS) is the act of detection and(or) identification o f an object, series of objects, or landscape without having the sensor in direct contact with the object (Frazier et al., 1997). Agricultural applications o f r e m o t e sensing generally involve detection of electromagnetic energy p h e n o m ena, such as light and heat. Sensors can measure energy at wavelengths that are beyond the range of h u m a n vision (ultra-violet, near infrared, or thermal infrared) and thus can provide information about subtle changes within a field or crop that could not otherwise be detected or quantified. Digital imagery for RS may be obtained from either an orbiting satellite or from an airplane fly-over, d e p e n d i n g o n the location, type of crops being grown, and desired use of the information. Currently, satellites have the potential to obtain images o f a given area o f interest (field) approximately five to seven times in a 3-week period, with a resolution o f 10 m or less at a cost of $1.25/ ha per time period. T h e r e can be wide variation in results and p e r f o r m a n c e a m o n g satellites, and usefulness may be limited by
cloud cover. Airplanes can provide images based on the specific needs o f the producer, typically at a cost of $15 to $ 3 7 / h a for 16 to 36 images. Airplane imaging can be timed to coincide with critical periods of crop develo p m e n t and can be scheduled a r o u n d bad weather. Imagery from airplane fly-overs is limited to areas where such technology is available. T h r e e types o f resolution (spatial, spectral, and temporal) n e e d to be considered w h e n discussing digital imaging. Spatial r e s o l u t i o n is the distance b e t w e e n data points (e,g., a resolution of 10 m would give 100 data p o i n t s / h a ) . Improvements in spatial r e s o l u t i o n have p a r a l l e l e d improvements in satellite technology. Spectral resolution is the variation of light energy and the m e a s u r e m e n t o f the portions o f such energy reflected, absorbed, and transmitted from an object or location. These differences permit the user to distinguish between different features on an image. Understanding what those differences depict is the critical part. T e m p o r a l resolution refers to repeated imaging o f the same field or crop on successive dates, thereby providing a record of changes over time. How often remotely sensed images are n e e d e d varies greatly with the type of crop grown and how often the grower plans o n p e r f o r m i n g a field operation based on the data received. Therefore, a n o t h e r important factor to consider when deciding on an imagery service provider is the time required before the images are available for use (e.g., a 1-week delay may be acceptable for some crops, but not for others). Remote Sensing has a wide range o f potential applications including detection of crop stress; monitoring variability in crops, soils, weeds, insects, and plant disease; detection o f unusual conditions, such as broken drainage tiles or crop injury during cultivation; yield estimation, which is highly dep e n d e n t on the type and variety o f crop; and GIS applications. Digital imagery provides access to repeated observations of a field during the growing season to help explain c h a n g e s as t h e y h a p p e n a n d while the grower has time to respond.
434 Journal of Nematology, Volume 30, No. 4, December 1998 VARIABLE RATE TECHNOLOGY
Variable Rate Technology (VRT) refers to the instrumentation used for regulating application rates of fertilizer, lime, pesticides, and seed as an applicator travels across a field, based on a decision support system and(or) m a n a g e m e n t plan. VRT resembles a back-to-basics approach to farming, with varying inputs across a field d e p e n d i n g on a n u m b e r of field and p r o d u c t i o n variables. T h e information n e e d e d to support VRT may come from several sources such as GPSr e f e r e n c e d data, RS images, a n d GISgenerated maps. All of the data are used to p r o d u c e a site-specific a p p l i c a t i o n plan based on sound agronomic principles. Current VRT e q u i p m e n t allows the user to m o n i t o r machine functions as mechanical applicators quickly react to changes in field conditions and make adjustments to field operation (seeding rates, fertilizer and c h e m i c a l a p p l i c a t i o n rates, etc.). W h e n coupled with a GPS receiver, VRT provides the controlling mechanism to make adjustments based o n the location o f invisible lines p r e d e t e r m i n e d by the farm manager or e q u i p m e n t operator. VRT provides the opportunity to manage p r o d u c t i o n based on soil type, soil texture, organic matter, nutrient levels, soil pH, weed and insect populations, disease, spatial pattern o f n e m a t o d e populations, desired yield, and o t h e r factors. PRECISION FARMING
Precision Farming (PF) combines the best available technologies to provide the information n e e d e d to make soil and crop mana g e m e n t decisions that fit the specific conditions f o u n d within each field. Precision Farming, also called Site-Specific Farming, uses GPS, GIS, and RS to revolutionize the way data are collected (at resolutions of 1 to 5 m) and analyzed to enable more informed m a n a g e m e n t decisions. Today, the potential exists to have detailed records covering evel I phase of the crop p r o d u c t i o n process, thus e n h a n c i n g sound business decisions. T h e cost of adopting the new technologies, and the time required for their implementation and use, are two factors that n e e d to
be considered when judging the added bene fits for decision making. The use of PF can provide n u m e r o u s benefits: (i) greatly improved ability to identify, diagnose, and communicate crop and field problems; (ii) i m p r o v e d e q u i p m e n t efficiency through better scheduling, sequencing of equipment, planning o f field operations, e q u i p m e n t movement, etc.; (iii) risk r e d u c t i o n t h r o u g h r e d u c e d variability in growing conditions, improved varietal choices, crop rotation, etc.; (iv) improved monitoring and supervision, including better records of field operations, location of e q u i p m e n t , p r o d u c t i o n output, and employee performance; (v) improved records pertaining to p r o d u c t i o n processes, crop conditions, and r e q u i r e d inputs; (vi) increased d o c u m e n t a t i o n o f food safety; and (vii) e n h a n c e d environmental stewardship through more accurate and precise application of chemicals and fertilizer to reduce the potential for leaching and runoff. This last benefit, environmental stewardship, is perhaps the m o s t i m p o r t a n t f a c t o r o f the group. Such stewardship does not h a p p e n automatically b u t must be i n c o r p o r a t e d t h r o u g h o u t the PF decision support system. CONCLUSIONS
GIS, GPS, and RS can provide producers with the m a n a g e m e n t tools to reduce risk. Producers now have simultaneous access to the n u m e r o u s types of data n e e d e d to make more informed m a n a g e m e n t decisions. To better utilize the precision graphical maps that can be generated today, producers must u n d e r s t a n d the information contained in the images and be able to use that information to change the way fields are managed. The ability to use such information is m o r e a function of agronomic skills than of limitations imposed by technology. T h e r e may be practical limits regarding location size that influence whether changes in managem e n t are justified in terms of economic or environmental returns. Some Internet sites with relevance to topics discussed in this article include: GIS:(http://wwwscas.cit.cornell.edu/ landeval/gis.htm) and (http://www. usgs.gov/research/gis/workl.html)
P r e c i s i o n F a r m i n g T e c h n o l o g y : Strickland et al. GPS:(http://www.unavco.ucar.edu/) and (http://www.utexas. edu/depts/grg/ gcraft/notes/gps/gps.html) RS:{http://www.geo.mtu.edu/rs) VRT:(http://nespal.cpes.peachnet.edu/pf/ vrt.stm/) LITERATURE CITED Aronoff, S. 1989. Geographic information s~tems: A management perspective. Ottawa, Ontario: WDL Publications.
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Frazier, B.E., C. S. Walters, and E. M. Perry. 1997. Role of remote sensing in site-specificmanagement. Pp. 149-160 in F.J. Pierce and E.J. Sadler, eds. Th e state of site-specific management for agriculture. Madison, WI: American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. Lange, A. F. 1996. Introduction to differential GPS for precision agriculture applications. In Proceedings of the 1996 Information Agriculture Conference. Atlanta, GA: Potash and Phosphate Institute. Morgan, M. T., and D. R. Ess. 1997. The precisionfarming guide for agriculturists. Moline, IL:John Deere Publishing.
