Traditional farming approaches
Traditional arable management practices have developed towards managing fields in a uniform manner, with pressures from mechanization leading to increases in field sizes. However, it is now widely recognized that soil type and structure can differ over short distances, and this variability increases with field size. Topography, ancient earthworks, drainage patterns, and exposure to shade will all influence the soil characteristics in a particular area. Since differences in the soil affect crops and thus yield, it is clear that more accurate agricultural management has the potential to benefit the farmer financially and the environment.
Economic and Environmental Considerations
Economic analysis of treatment measures and yields is critical to successful agricultural management. The yields of a crop generally increase with increasing fertilization, although the rate of increase tends to decrease as more and more nutrients are added. Eventually, a point is reached where the yield increases do not justify extra fertilizer costs, and maximum economic yields are obtained. When this point varies within fields, spatially variable fertilizer application ensures maximum yields across all fields. Furthermore, excess nutrients can cause quality problems in some crops such as nitrogen in sugar beet and potatoes. Over-application of fertilizers also increases the chance of environmental problems via nutrient leaching and runoff. Similarly, inappropriate application of pesticides to crops can add considerably to farming expenses. Over-application not only adds to the cost of pesticides but also increases the risk of groundwater contamination, and poses a health risk to the operator. Under-application may result in inadequate pest control affecting the yield cost.
Introduction to Precision Farming
"Precision farming" refers to the careful tailoring of soil and crop management to different conditions found in each field. Sometimes known as "prescription" or "site-specific" farming, precision farming applies a combination of new technologies in order to optimize farm inputs, improve efficiency and reduce environmental pollution. Key technologies involved in precision farming include Global Positioning Systems (GPS), Geographic Information Systems (GIS), and Variable Rate Treatment (VRT).
The precision farming procedure can be summarized as follows. Data pertaining to yield and potential yield-affecting factors are initially collected and then analyzed to determine which factors are actually affecting the yield. If yield is being affected, a farm manager decides the type, distribution, and amount of treatment to apply. Remedial measures can then be carried out to ensure that the correct treatment is applied at the required rate and to the appropriate area within a field. In effect, the spatial variability in the field is managed through the manipulation of inputs such as fertilizers and pesticides.
Variable application of inputs may not always increase yields, but simply hold them constant whilst reducing input costs. Precision farming enables the farmer to reap increased profit through better management, and the application of more appropriate/reduced chemical treatments also helps to preserve the environment.
Implementing Precision Farming
Information is required on how and why the field conditions vary i.e. the collection of geo-referenced environmental data (yield and soil sample data) in order to generate yield maps. There are several techniques that allow this but the two main ones is:
Direct Field Attribute Measurement
Manual grid sampling is highly accurate but is both expensive and labor-intensive. An exciting development is that of adapted combine harvesters that have a vehicle positioning system integrated with a yield recording system. Vehicle positioning systems rely on GPS (Global Positioning Systems) technology and a series of military satellites. The GPS alone only provides an accuracy of around 100m. The use of military satellites (or other reference stations) allows this accuracy to be corrected. This allows the vehicle location to be identified within a meter of its actual site in a field and expresses coordinates in terms of longitude and latitude. This technique is known as DGPS (Differential Global Positioning Systems).