Precision Soil Sampling
Soil sampling is an important step in site-specific crop management as soil variability is often directly correlated to variations in yield. Traditional soil sampling consists of collecting and compositing random samples from across a field resulting in a uniform application of fertilizer and lime. This broad application often leads to an over- or under-application of plant nutrients. Precision soil sampling is accomplished by geo-referencing soil samples from the area which the sample was taken using a Global Positioning System (GPS). This allows growers to manage field variability by optimizing nutrient and lime inputs on a site-specific basis. Precision soil sampling is accomplished through either zone or grid sampling methods.
Guidance
The advent of GPS has permitted manufacturers to develop systems which help farmers “guide” their equipment when traversing fields in order to maintain the desired path. These guidance systems reduce application overlap or skips, improve in-field efficiency, and the ability to work at night leads to cost savings for producers. Guidance has been one of the most adopted PA technologies to-date by farmers, custom applicators, and others. These systems come it two basic forms: manual and automated guidance.
Manual Guidance
The equipment guidance system that is the simplest and least expensive for farmers to adopt is the lightbar. Lightbar guidance systems require the operator to still drive the vehicle with the lightbar providing navigation cues to the driver based on the GPS location and swath width of the equipment. Newer lightbar systems feature last-pass-guidance, color screens and as-applied mapping. These systems are most frequently used for spraying and fertilizer applications as well as for harvesting hay. Units typically provide 4” to 12” pass-to-pass accuracy.
Automated Guidance
Auto-steer guidance systems work along the same principle as lightbar systems, but they actually steer the machinery instead of the equipment operator. In this case, the vehicle drives itself allowing the operator to concentrate on other operational functions or relax. The operator must manually turn the equipment at field ends. Assisted steering devices can provide 2” – 12” accuracy depending on the GPS correction utilized for the application. Auto-steer systems utilizing Real-time kinematic (RTK) can provide year-to-year repeatable accuracy to the sub-inch level. Applications for RTK auto-steer guidance include planting, harvesting, installing drip irrigation and controlled traffic patterns.
Variable Rate Technologies
Variable-rate technology (VRT) describes any technology which enables producers to vary the rate of crop inputs. VRT combines a variable-rate (VR) control system with application equipment to apply inputs at a precise time and/or location to achieve site-specific application rates of inputs. A complement of components, such as a DGPS receiver, computer, VR software, and controller are integrated to make VRT work. A site-specific approach allows growers to apply products only where they are needed in a field. Varying the application of inputs can reduce input and labor costs, maximize productivity, and reduces the impact over-application may have on the environment. Examples of VR applications for agriculture include fertilizer, lime, seeding and pesticides.
GPS/GIS
The Global Positioning System (GPS) and Geographic Information Systems (GIS) provide farmers with the capabilities to manage field variability on a site-specific basis. GPS is a constellation of 24 satellites orbiting 12,660 miles above the Earth that is used for determining latitude and longitude (position). When installed on agriculture equipment, a GPS receiver provides position information for soil sampling, crop scouting, applying inputs, planting, harvesting and other applications. A GPS receiver allows farmers to continually return to the same location in a field.
A GIS retrieves, stores, and analyzes spatial data and can be used to generate field and prescription maps for application of crop inputs. GIS data and maps are used for management decisions such as management zone creation, variable-rate application, planting decisions, and targeted soil sampling. Delineated management zones in GIS are used to site-specifically manage cropland according to measured field and/or crop variation. Farmers are able to use GIS to produce detailed harvest reports, determine trends from harvest to harvest, and compare production capabilities of different varieties and crop inputs. Agriculture GIS software can also serve as valuable accounting, record keeping, and decision support tools for farmers.
Yield Monitoring
Yield monitors use GPS, GIS, a computer, and sensor technologies to accurately measure the amount of crop harvested at a specific location and time. Yield monitors are installed on harvesting equipment and are used on a variety of crops including corn, wheat, soybeans, sugar beets, potatoes, and cotton. In addition to measuring yield, these systems allow for the recording of crop moisture, elevation, variety, and a number of other harvest variables. Yield monitors use sensors to measure the crops’ mass or volume and are found to be accurate to +/- 3% of actual harvested amounts, but require routine calibration to maintain accuracy. The volume or mass measurements are recorded in the on-board computer to produce indirect yield measurements. GPS provides the field location for each measurement. The location and yield data are recorded onto a storage device and transferred to a desktop AgGIS package for processing, viewing, and analysis. Maps depicting yield variations across fields can be developed and used to provide farm management decisions to improve crop productivity.
Remote Sensing
Remote sensing obtains information about an object without directly contacting it. In an agricultural environment, information about the soil or crop is usually gathered from a plane-based, satellite-based, or agricultural equipment-based sensing device. Data collected can range from a simple color photograph to the crop’s emission of electromagnetic energy. Remotely sensed data can provide farmers real-time information regarding their crop condition, allowing them to respond and make corrective or other management decisions to maximize crop production. Data can be collected for an entire field with remote sensing as compared to traditional scouting methods which only provides single point or partial field coverage during the growing season. Data collection over multiple dates during the season allows farmers to monitor both positive and negative trends in crop progression. Examples of remote sensing tools used in agriculture include aerial photographs, near-infrared (NIR) date, and thermal imagery. Integrating remotely sensed data into a GIS can reveal information about soil characteristics and general crop health that can be a valuable tool for site-specific management.
