Precision Agriculture

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

Data Collection

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).

• Remote Sensing

Remote sensing using aerial photography or satellite imaging provides the opportunity to collect large amounts of data, rapidly and at a relatively low cost. Long-range sensing can be used to determine soil type variation from aerial photos; variations in soil fertility are subsequently estimated. Other applications include assessing crop condition, weed infestation, crop stress, and insect infestation.

Data collection is a continuous process. A minimum of 3 years, and ideally 5 years of harvest data are required before it is possible to establish an agronomic blueprint for a given field. During this time other site-specific historic and observational data should also be collected and mapped probably by hand.

An onboard computer that can be used on a variety of field machines including combine harvesters, tractors, or light vehicles allows yield surveying, area measurements, and control of the machine for targeted application e.g. manures or crop protection sprays.

An important factor in the practical implementation of precision farming is reliable communication between the farm computer, onboard computer, and distributors. A LBS (Land Bus System) is a standardized interface between these devices which allows information exchange and so it is important that equipment purchased for precision farming supports this standard.

Data Analysis

A Geographical Information System (GIS) is a software application that is designed to provide the tools to manipulate spatial data. It is capable of storing, managing, analyzing, and displaying information related to geographical location, generally in the form of a map. The advantage of a GIS over traditional maps is that it allows different maps to be overlaid, producing new maps which highlight the interaction between various field characteristics. By comparing field characteristics to changes in the yield profile, it is possible to understand why some areas of the fields are more productive than others.

Yield maps not only provide information on the harvested crop but can also pinpoint problems that have been caused by the preceding crop. They can quantify financially the problems of increased compaction on headlands, and indicate failings with in-field drainage systems. Finally, information gained from yield maps can be used to assess unproductive area.

Variable Rate Treatment

Variable-rate treatments allow the farmer to utilize field variability information and plan inputs so that the best potential of the field is obtained. Recent development in seed drill technology has resulted in control systems that pass information between the tractor and seed drill. These systems deliver the required rate of seed, adjusting delivery on the move where necessary. Other examples include variable-rate fertilizer spreaders that adjust the application rate according to soil nutrient availability across the field. Herbicide application can also be controlled via flow rate, to match field weed incidence.

Precision farming does not imply any particular management technique. What it does do is allow the farmer a better understanding and greater control over the treatments to fields. The combination of farm machinery and computer technology is an extremely beneficial aid to the decision-making process in agricultural management.

The Pros and Cons

There are many benefits to precision farming but there are also a number of other issues which need consideration before adopting the technology.

Advantages

• GPS allows fields to be surveyed with ease.

• Yield and soil characteristics can be mapped.

• Non-uniform fields can be sub-divided into smaller plots according to their specific requirements.

• Provides opportunities for better resource management and so could reduce wastage.

• Minimizes the risk to the environment particularly with respect to nitrate leaching and groundwater contamination via the optimization of agrochemical products.

Disadvantages

Techniques are still under development and so it is important to take specialist advice before making expensive decisions.

• Initial capital costs may be high and so it should be seen as a long-term investment.

• It may take several years before you have sufficient data to fully implement the system.

• Extremely demanding work particularly collecting and then analyzing the data.

Posted By Niranjoy Yengkhom