Before the advent of large agricultural machinery, farmers had to plow behind a mule and harvest by hand. While this was back-breaking work, it gave the farmers an in-depth knowledge of the land's soils, landscape, and yield potential. Farmers adjusted their fertilizer applications to compensate for low and high yielding areas of the field. They knew how to manage site-specifically because the application of seed, agrochemicals, or organic matter was done manually. As the scale of agricultural machinery grew in the 20th century, farmers lost the ability to address the specific needs of individual areas within fields. Instead, production systems moved to larger fields fertilized or planted at rates representing field averages. Now, technological breakthroughs in communications, miniaturization of computer technology, development of sensors and detectors, and public access to GPS allow us to better address within-field variability with precision agriculture.
Precision agriculture is a catch-all term for techniques, technologies, and management strategies aimed at addressing within-field variability of parameters that affect crop growth. These parameters may include soil type, soil organic matter, plant nutrient levels, topography, water availability, and pest pressure. In turn, this allows us to maximize production efficiency and minimize environmental side effects by applying resources only where they are needed and at the amounts needed (Vellidis et al., 2001, 2003).
At the very core of precision agriculture is the network of satellites called the Global Positioning System or GPS. A GPS receiver/antenna can be placed on any piece of agricultural machinery and can provide accurate location information in terms of latitude and longitude. By linking GPS to yield monitoring devices, soil and pest sampling, remote sensing, and information such as topography, soil type, water patterns, previous and current cultural practices, a grower can create maps showing how these parameters vary within a field. The maps allow the grower to individually, rather than uniformly, manage areas within a field. These maps are most useful when stored in a Geographic Information System (GIS).
Using a GIS, a farmer can organize, manipulate and analyze the information about a particular field or a whole farm. A GIS can take layers of input, such as a weed infestation map, and create an output layer, such as a control map for herbicide application, which can then be used to direct herbicide application only in those areas infested with weeds.
Essential components of precision farming are yield monitors - sensors installed on harvesting equipment that dynamically measure spatial yield variability. Yield monitors for grain combines have been available for several years. Yield monitors for other crops, including cotton, have just recently been introduced to the market and are being evaluated by researchers. Yield maps are extremely useful in providing a color-coded visual image to a farmer clearly showing the variability of yield across a field. Coupled with GPS and an on-board computer, crop yield is recorded each second as the harvester travels the field. A yield map depicts yield for each location within a field. This provides the grower important information about the effects of management practices immediately after the growing season as well as information to guide future management decisions. With good record keeping, yield maps can be quickly converted to profit maps (Figure 1).
Another important component in precision agriculture is variable rate application (VRA). VRA refers to the ability to vary crop inputs according to need. This may be a change in fertilizer, pesticide, or irrigation rates from one area of the field to the next. Information such as soil nutrient concentrations is gathered from soil sampling. Using GPS, soil samples are geo-referenced and a map of nutrient levels is made in the GIS. Nutrient requirements are calculated for each area represented by a soil sample and a control map for fertilizer application is created. Using this control map, fertilizer rates are varied across the field as needed rather than applied uniformly. It is also possible to vary irrigation water, seeding rates on planters, and pesticide applications.
Fundamental to the philosophy of precision agriculture is the concept of matching inputs to needs. If a part of a field needs more fertilizer, give it more fertilizer. If a section of crop needs harvesting early, harvest it early. These are simple, common-sense ideas. However, like many good ideas, there is a significant gap between theory and implementation. In-field management zones are currently the most practical way to implement the theory of precision agriculture.
For more detailed information on precision agriculture, please visit our educational materials where you will find presentations covering 15 topics important to precision agriculture.
Precision Agriculture and Food Safety
Because agricultural commodities are now routinely traded and transported across the globe, there is increasing concern among consumers, regulators, and elected officials about food safety. Accurately knowing the ultimate source of the food supply can ensure improved quality and accountability. Having the ability to detect the presence of mycotoxins and other dangerous agents in food shipments without expensive destructive testing would greatly improve food safety. Commonly used sampling techniques are often destructive and grossly overestimate or underestimate toxin levels.
The same techniques, technologies, and management strategies used in precision agriculture can be applied to improving food safety by allowing seamless incorporation of "traceability of origin". Because a fundamental principle of precision agriculture is to attach traceable geographic coordinates to all farm activities associated with food production, it becomes a matter of associating those records with any product sent to market to have a complete history of the product available to regulatory agencies like the Food and Drug Administration (FDA) and public health agencies like the Centers of Disease Control (CDC) which investigate food-borne disease outbreaks. Traceability of origin can also be an extremely valuable tool to custom agents at ports of entry who are assigned the initial responsibility of authorizing the entry of commodities.
An important growth sector of precision agriculture is the development of biological and electronic sensors with the ability to detect minute amounts of organic and inorganic compounds in the air. Almost all living organisms exude a unique mix of organic volatile compounds in trace amounts. The mix of compounds is as unique as the human fingerprint. Sensors which sample the air and identify the presence of organic volatiles can be used as sentinels (Rains et al., 2000, 2001).
Under conventional agricultural applications, these sensors would detect the presence of plant disease or destructive insects. In food safety applications, the sensors can be used to detect naturally occurring toxins commonly known as mycotoxins in grains, fruits, vegetables, and commodity storage facilities or dangerous pathogens that threaten our food supply. Perhaps even more importantly, these sensors can be used to safeguard against food stuffs inoculated with pathogens or other dangerous agents. One example often debated in food safety circles is the contamination of animal feed (which are shipped all over the planet) with a pathogen that would result in a pandemic in livestock. Such a pandemic would have a devastating effect on the economy of any stricken nation. The recent mad cow disease outbreak in Europe, Canada, and the United States is an example of how animal feed contamination can have severe economic and human health impacts.
Adoption of Precision Agriculture
Precision agriculture (PA) adoption rates are dramatically different across the globe with the highest adoption rates in the United States and the European Union. The corn belt is the most intensive user of PA technology in the U.S. However usage in California and the southeast is rapidly increasing. In these areas, farmers are actively using PA technology and practices and business have started up that market PA equipment and services. In fact, all three U.S. partners have been the source of spin-off PA companies.
In the EU, the largest users of PA are the United Kingdom, Denmark, Sweden, and Germany. The Mediterranean nations (Greece, Spain, and Italy) are far behind in the adoption of PA where it is still mostly relegated to research projects at universities. Nevertheless, a few established agribusiness are beginning to offer PA services to farmers. In Greece for example, Papaeconomou Agrochemicals (www.pap-agro.gr) has been offering various PA services to its clients since 2001. This occurred only because the company's CEO conducted his Ph.D. on PA at a US university.
The United States and the European Union are under great pressure from the World Trade Organization (WTO) and from each other to reduce agricultural price support programs and allow their farmers to compete openly on the world market. Consequently, US and EU farmers face many common issues – how to compete in the global market while farming under the constraints of high input costs, high labor costs, and restrictive environmental and food safety regulations. Precision agriculture provides the tools and techniques to greatly improve the efficiency of production and make US and EU farmers more competitive. Deterrents to adoption have been the relatively high capital investment and steep learning curve needed for most PA-related equipment. As more users enter the market, prices have begun to decline. For example, a good quality GPS receiver cost more than $2000 just 5 years ago. Today, the same quality receiver can be purchased for under $500. However, the lack of proper training opportunities with which producers can overcome the steep learning curve remains an important deterrent to adoption. This obstacle can be overcome with trained professionals who can promote and facilitate the use of PA across national boundaries for the benefit of agriculture, food safety, and the environment.
References
Rains, G.C., M.D. Alessandro, and W.J. Lewis. 2001. Identification and detection of volatile compounds from sensing plant stress. ASAE Paper No. 011069. St. Josephs, MI: ASAE.
Rains, G.C., T. Meiners, K. Takasu, D.M. Olson, W.J. Lewis, J.H. Tumlinson, Y. Cardoza. 2000. Development of a programmable whole-organism wasp sensor for monitoring crop conditions from volatile chemicals. ASAE Paper No. 003062 St. Josephs, MI: ASAE.
Vellidis, G., C.D. Perry, J.S. Durrence, D.L. Thomas, R.W. Hill, C.K. Kvien, T.K. Hamrita, and G.C. Rains. 2001. The peanut yield monitoring system. Transactions of the ASAE 44(4):775-785.
Vellidis, G., C.D. Perry, G. Rains, D.L. Thomas, N. Wells, C.K. Kvien. 2003. Simultaneous assessment of cotton yield monitors. Applied Engineering in Agriculture 19(3):259-272.