Yield monitoring systems allow yield variations to be measured while a paddock is being harvested.
Maps which show yield variation are produced by equipping a harvester with a yield monitor, a DGPS and a data logger. Sensors can also be fitted to monitor ground speed and grain moisture. A yield monitor is used to measure grain flow as it is deposited in the grain tank.
Each second or two, while harvesting the crop, the harvester's position in the paddock and the grain flow are recorded in the data logger. Some units can record information on weed levels in crops.
A switch located on the yield monitor is turned on when the harvester moves into a weed patch and then turned off when the harvester moves out of the weeds.
After about a day of harvesting the data logger can be downloaded onto a computer.
Yield maps are then produced using specialised software. There are two types of yield monitors currently available in Australia. One type measures the weight (mass) of grain when it is discharged into the grain tank. Examples of these include the AgLeader, Micro-Trak and John Deere systems.
The other type senses the volume of grain as it is delivered to the grain tank — for example the Satloc and Farmscan units. The Satloc unit measures the volume of grain as it passes up the clean grain elevator. The Farmscan unit uses a turbine to calculate the volume of grain as it flows up the 'bubble up' auger (see picture 3).
The disadvantage of the volume measurement systems is that they assume a fixed density of grain. This means the sensors used on these devices need to be calibrated correctly.
The AgLeader yield monitoring system is manufactured in Iowa, USA.
The system is being imported into Australia and distributed by Pathway Precision Farming Systems in Victoria and Rinex Technology in WA. The AgLeader yield monitoring system is supplied to fit any harvester. The system consists of a mass-flow yield monitor, a moisture sensor and a display-control panel. A PC card is supplied to record data.
The unit comes with a mounting kit and detailed manual.
The AgLeader yield monitor is available from Rinex Technology for about $6,500. The OmniStar DGPS can be hired for the harvest period for $2,700 plus $1.40/ha which includes a yield mapping service.
Buyers also have the option to buy the DGPS unit which provides unlimited use throughout the harvest period.
With this option the yield mapping provided by the company is limited to 2,000 ha. This package costs about $19,000.
AgLeader has also developed a device to mark the location of weeds within a paddock.
The Farmscan yield monitor is undergoing development. The company has released the Satlink 3000 which provides the in-cab control link to Precision Farming technologies. The device links DGPS data together with application maps and provides direct control over variable rate air seeder drives and spray control valves.
New Holland, North America, is completing field tests of its Precision Land Management System which includes an Accu-wave yield monitor sensor and display, DGPS and field mapping software. The system can be fitted to older model New Holland harvesters. The company estimates the new system will be available in Australia by 1998. The firm is also testing a GPS linked robotic windrower which may be a sign of things to come.
The AGCO/Massey Ferguson Fieldstar Precision Farming System is still being developed but versions have been sold in Europe since 1991.
The unit uses a mass grain-flow sensor, moisture sensor, display control panel and a PC card storage system.
The company claims the system has been successful in Europe for a number of years and proved very accurate. The same operator console is used in both the harvester and the tractor.
The yield monitoring system will be available for the Gleaner, Massey Ferguson and Claas harvesters.
The system will be available to Australian growers later this year.
Case IH Corporation
p>Case IH has developed a yield monitoring system known as the Advanced Farming System which is being imported from the US for trial in Australia. The system includes a massflow yield monitor and yield mapping software. Flow and moisture sensors are fitted to the monitor and the system uses satellite DGPS to correct signals.
The GreenStar yield mapping system is manufactured in the US and imported by John Deere for distribution in Australia. The yield mapping system collects positioning and correction data as well as information on yield and moisture.
A mass-flow yield monitor is standard and position signals are corrected using a satellite DGPS. Buyers are provided with a yield monitoring system, computer software called JDMap, and a Windows '95 based program.
The Micro-Trak range of yield monitoring equipment is manufactured in the US and distributed in Australia through Croplands Precision Agriculture. The company provides two options — a yield monitoring kit and a yield mapping package.
The Micro-Trak yield monitoring kit includes a Grain-Trak mass-flow yield monitor and display unit.
The kit costs $4,680 including installation. The yield mapping package includes a Data-Trak logger, PC card reader, a 2MB PC card, yield mapping software and the hire of a DGPS unit for 150 hours. The package costs $4,200 including installation. An optional moisture sensor can be fitted for $1,010.
Richard Barrett, Corrigin, WA, has been using Micro-Trak Grain-Trak since the 1995-96harvest. Richard said the Grain-Trak unit is accurate as long as it is calibrated correctly.
The Satloc yield monitoring system is being imported from the US and distributed in Australia by Gwydir Air at Moree, NSW.
The system includes a yield monitor, moisture sensor, data logger and yield mapping software.
The data logger can also be used to record weed information. The yield monitor has a through-beam photoelectric sensor, fitted to the clean grain elevator, which measures the volume of grain being delivered into the grain tank. This measures the volume of grain by recording the time the light beam is broken by the grain.
A speed sensor is fitted and a switch is provided to stop the sensor when turning on headlands.
The system costs about $8,100 which does not include installation but does include a DGPS receiver.
Handheld GPS receivers
Handheld GPS receivers are not accurate enough for use in precision farming.
The receivers are mainly used as navigational tools by fishermen, outback travellers and others who only need to be within 100-300m of their true position. There is a large range of handheld GPS receivers on the market ranging in cost from about $500-$5,000 depending on quality and features.
The receivers are available from a number of suppliers in the yellow pages listed under GPS. These devices can be used on farms with a differential correction receiver which fits into a backpack. The receiver is powered from a battery in the backpack.