| Fertilizers

Advances in fertilizer distribution methods and their benefits

Systems that configure the automatic fertilizer distribution controller at a variable or fixed rate have been designed to operate in conjunction with any type of belt distributor and spreading discs

23.10.2017 | 21:59 (UTC -3)

The great evolution of Brazilian agriculture in recent decades has practically doubled the productivity of some crops, although without increasing the size of productive areas to the same extent. Precision agriculture fits into this context, offering producers management tools and detailed monitoring of their crops, surveying details of crops during each stage of the production cycle, in addition to providing increased productivity and reducing the amount of inputs applied.

One of the segments of precision agriculture is the distribution of fertilizers at a variable rate, which is based on recommendation maps for correction and fertilization, generated from historical productivity, treatment processes and laboratory analyzes of the soil. The objective is that each small part of the soil receives the amount of input it needs, and not an average dose as is done in conventional agriculture, obtaining homogeneity of the crop, increased productivity and mainly profitability due to cost reductions.

A variable rate system is basically made up of a broadcast fertilizer spreader and an electronic controller. The distributors are built with a storage tank, spreading discs, gate and can be assembled with or without a conveyor belt. The distributors most used in automated variable rate systems have a conveyor belt, although it is also possible to control the application rate in distributors without it.

The electronic variable rate controller must have a module for receiving signals from American (GPS) and/or Russian (GLONASS) satellites to calculate the geographic position and speed of movement of the distributor (the speed can also be measured through sensors in one of the implement wheels). The controller relates this position to the target rate identified in the recommendation map inserted into the equipment and controls a hydraulic motor to obtain the desired rate.

The target rate is achieved by controlling the belt rotation speed which is measured via a rotation sensor (encoder) coupled to it. After calibrating the system with the desired fertilizer, the controller relates the conveyor speed to the quantity of product distributed. This relationship varies according to the fertilizer to be distributed and the opening of the gate during the calibration process.

The gate may or may not be automated. In the most common case of manual opening, the gate is maintained in a fixed position chosen by the operator, limiting the range of application. The controller will be limited to a minimum and maximum distribution rate determined by the opening of the gate. Gate automation aims to resolve this limitation, as the controller can automatically move it to achieve different application ranges without the need for new calibration.

The product carried by the conveyor out of the tank falls onto the spreading discs, which have the function of distributing the fertilizer evenly. By varying the position of the fins and the rotation of the discs, the width of the application range varies. Distributor manufacturers provide a table that indicates the correct disk configuration for each type of product and desired bandwidth. The discs can be rotated through a coupling to the tractor's cardan shaft or through a hydraulic motor. In the second case, control can be done by an electro-hydraulic valve from the electronic controller or by a manual valve. The electronic control facilitates rotation adjustment and allows greater stability in the movement of the discs and, consequently, greater homogeneity in the application width.

Application recommendation maps are generated in format shapefile and inserted into the electronic controller using a pen drive. O Esrishapefile, or simply shapefile, is a popular type of file that contains georeferenced polygons with target application dose information for different products.

An example of this type of application is the Agronaveda system from the company Agrees, which operates in the configuration of an automatic fertilizer distribution controller at a variable or fixed rate. Designed to operate in conjunction with machines that use conveyor technology and spreading discs as a means of distributing fertilizers, in powder or granule form, the system can be installed on any type of distributor: coupled, trailed or self-propelled. Installation kits are provided for precision agriculture ready and unready distributors. (see box)

The main component of the Agronave system is the on-board computer. The computer has a 5,7-inch color screen, displays the recommendation map during navigation and records the entire application trail, as well as any overlaps. It controls the speed of the belt and, as an option, it can control the speed of the discs, which facilitates the adjustment of the distribution width, and it can control the opening of the gate, which allows greater variation between application rates without the need for new calibrations.

Recommendation maps for variable rate application are inserted into the on-board computer without the need for any prior conversion. The format map shapefile is recorded in the equipment's internal memory. Application and configuration information as well as navigation maps can be downloaded via pen drive directly from the on-board computer for subsequent analysis.

The complete solution has a high level of robustness, being resistant to high temperatures, chemicals, adverse agricultural conditions and overloads (motor starting, short circuit or improper connections). The high-resolution belt rotation sensor at low speeds provides great accuracy in the target rate of fertilizer to be distributed and eliminates mounting problems due to elastic or magnetic coupling.

For an even more precise variable rate application, Agronave offers automatic pilot as a solution. In both versions – electric and hydraulic, the automatic pilot combined with the automatic cut-off of fertilizer distribution minimizes overlaps and application errors, in addition to ensuring that the distributor always runs on the same track throughout the preparation.

BOX

Items used in fertilizer applicators for variable rate application

ITEM	Kit for Distributors prepared for Precision Agriculture	Kit for Distributors NO prepared for Precision Agriculture
On-Board Computer + GPS Antenna	X	X
Encoder 1000 pulses per rotation	X	X
Electrical cabling for installation	X	X
Hydraulic engine		X
Hydraulic Block with Solenoid Valve		X
line filter		X
Supports for fixing items	X	X
Motor/Track Shaft Coupling		X