VRA, short for Variable Rate Application, means that the spray output does not remain the same everywhere during spraying. The application is based on field information and on what is needed at that specific location. This fits within precision agriculture: using field information to better determine what is needed per field, zone or plant. For growers who want to work more precisely with applications such as desiccation, fertilisation, growth regulation, crop protection and row spraying, VRA is becoming increasingly important.
Within WEED-IT, VRA can be applied in different ways. With WEED-IT AQRATE the focus is on accurate PWM nozzle control and prescription-map-driven spray output. With WEED-IT QUADRO, VRA can also be based live on Crop Density Data (CDD). The sensor measures chlorophyll fluorescence; that value provides a practical indication of the amount of green leaf material and biomass in the crop. Based on this, the system can determine live which spray output is needed in that specific location. Field information can also come from satellite images, soil maps or drone images.
With a fixed spray output, a field is treated as if every square metre is the same. In practice, that is rarely the case. There are differences in crop density, soil type, organic matter, moisture status, biomass and weed pressure. Yet an average spray output is often chosen for the entire field.
Variable Rate Application turns this into a more flexible application. The spray output can vary based on prescription maps or real-time information from the field. The goal is not simply to spray less, but to spray better. In places where less is needed, less is applied. Where more is needed, more is applied, always within the maximums that apply to the product. As a result, the standard or base spray output normally used across the whole field can often be reduced. This has benefits for the crop and the soil.
A short distinction is important here. For crop protection products, dosage is the amount of product per hectare, as stated on the product authorisation label. For liquid fertilisers or growth regulators, it is the set amount of product per hectare. Spray output is the amount of spray solution per hectare. With PWM nozzle control, it is mainly the spray output that can be varied. The dosage or product concentration in the tank mix remains the starting point, but in places where the spray output is reduced, the crop or soil also locally receives less product solution.
A sprayer does not always operate under exactly the same conditions. Speed changes and bends require correction. Without accurate nozzle control, this can affect the actual spray output per hectare and the distribution in the crop or on the soil.
For the user, this is a recognisable problem. You set the machine correctly, but in practice the situation changes continuously. This can create areas with too much or too little spray output. In bends, for example, too much product can end up on the inside of the bend, with visible crop damage as a possible result.
Field example: in this bend, too much herbicide has ended up on the inside. As a result, beet plants have been severely damaged or died off locally.
The example above mainly shows why PWM nozzle control is important. PWM ensures that the right amount ends up in the right place, even when speed, bends or nozzle positions require correction. VRA adds the decision rule: which spray output do you want in which location, based on field information? The combination of PWM and VRA makes prescription-map-driven or live variable spray output reliable and controllable with WEED-IT AQRATE and WEED-IT QUADRO.
WEED-IT uses PWM technology, short for Pulse Width Modulation. This allows the spray output per nozzle to be adjusted without the pressure constantly having to change as well. That is important, because stable pressure helps keep droplet size and coverage constant.
With prescription-map-driven VRA, the desired spray output per zone is determined in advance. In combination with WEED-IT DASH prescription maps can be used to carry out applications at a detailed level. DASH is required for this; WEED-IT AQRATE and WEED-IT QUADRO are now supplied with DASH as standard. This makes VRA not just a theoretical possibility, but a practical way to control the spraying strategy per field.
With live VRA using WEED-IT QUADRO, CDD (Crop Density Data), the measured chlorophyll fluorescence per 25 x 25 cm, is translated directly into a spray output per nozzle. The user setting determines how many l/ha correspond to a certain CDD value. The system then automatically adjusts the spray output while driving.
With WEED-IT QUADRO, CDD data is mapped during every spraying operation. This creates an additional layer of field information that can be used directly for live VRA and later help users better understand variation within a field. WEED-IT can also combine variable spray output with spot or row recognition, so that the question of where to spray and the question of how much output is needed are controlled together.
The reason for using VRA is often the variation within a field. Crop stand, biomass, soil and weed pressure are not the same everywhere. Lower product use can be an important benefit of VRA, but it is not the whole story. For many growers, it is mainly about using products more optimally: sufficient effect, less risk of crop damage or growth suppression, better support for crop growth and yield, and more careful application towards the soil. This is relevant not only for crop protection, but also for applications such as desiccation, liquid fertilisation, growth regulation and row spraying.
One example is VRA with prescription maps for soil herbicides. On lighter soil types, a lower spray output may be sufficient for good weed control, while limiting growth suppression in the crop.
Spot spraying based on a prescription map is not the same as VRA, but it can be combined with VRA. A drone can, for example, accurately determine the position of volunteer potatoes in sugar beet or onions, or broad-leaved dock in grassland. The sprayer with WEED-IT then executes the prescription map site-specifically and can vary the spray output per location when needed.
Live VRA based on CDD is interesting when the measured amount of green leaf material and biomass can be used directly to determine the desired spray output. This can, for example, help with the variable application of liquid nitrogen in cereal crops. Because WEED-IT QUADRO records CDD data during every spraying operation, it also creates an up-to-date picture of variation within the field.
VRA is not a separate spray mode, but a way to control spray output within the chosen spraying strategy. In a full-field application, spray output can vary per zone. With spot spraying, detection or a prescription map determines where spraying takes place. With row spraying, row recognition determines where the spray output should end up. In combination with VRA, the required spray output can then be determined per location, target or row.
The WEED-IT spray modes help users choose the right way of working for different situations in the field.
WEED-IT AQRATE and WEED-IT QUADRO can both play a role in this. WEED-IT AQRATE focuses on accurate PWM nozzle control and prescription-map-driven spray output. WEED-IT QUADRO also makes live VRA possible based on CDD. This makes variable spray output part of a more practical and more controllable spraying process.
VRA is especially relevant for growers, contractors and companies that want to get more out of their existing sprayer. It is for users who want more control over spray output, want to adapt their application more closely to field variation and want to work more precisely in desiccation, fertilisation, growth regulation, row spraying or crop protection.
Within the WEED-IT product range VRA is relevant for companies that want to know not only where they are spraying, but also exactly how much is being applied and on the basis of which field information.
That makes WEED-IT interesting for those who want to progress step by step in precision spraying. Depending on the application, this can be done with prescription maps, live measurements, individual PWM nozzle control, spot or row recognition, or a combination of these.
The move towards VRA comes from a practical need. Growers do not want to apply more than necessary, but they also do not want to risk an insufficient result in places where more is needed. Variable spray output helps them find that balance more effectively within the variation of a field.
With WEED-IT, VRA becomes concretely applicable in the field. The combination of prescription maps, PWM nozzle control, individual nozzle control, spot and row recognition, and live CDD makes it possible to work more accurately without constantly having to make manual adjustments.
VRA stands for Variable Rate Application. It means that spray output during spraying can vary based on field information, prescription maps, live measurements such as CDD or a combination with spot or row recognition.
For crop protection products, dosage is the amount of product per hectare, as stated on the product authorisation label. For liquid fertilisers or growth regulators, it is the set amount of product per hectare. Spray output is the amount of spray solution per hectare. With PWM nozzle control, it is mainly the spray output that can be varied; as a result, the amount of product solution received locally can change.
WEED-IT can carry out VRA with prescription maps and, with WEED-IT QUADRO, also live based on CDD. Variable spray output can also be combined with spot and row recognition. WEED-IT QUADRO maps CDD data during every spraying operation. WEED-IT AQRATE and WEED-IT QUADRO accurately control spray output at nozzle level, while pressure and droplet size remain stable.
No. Spot spraying and VRA answer different questions. Spot spraying determines where spraying takes place: only on a detected or predefined target. VRA determines how much spray output is desired in a specific location. In WEED-IT, both can be combined, for example with spot or row recognition where spray output is controlled variably per location.
Because it helps align applications such as desiccation, fertilisation, growth regulation, row spraying and crop protection more closely with differences within a field. Spray output can be adapted to crop stand, biomass, soil or weed pressure. This has benefits for the crop and the soil.
Yes. VRA can be applied with prescription maps, where spray output per zone is controlled based on predefined field information. With WEED-IT, this can be done at a resolution of up to 25 x 25 cm; coarser is always possible. WEED-IT DASH is used for prescription-map-driven application. Prescription maps can also be combined with site-specific applications, such as spot or row spraying.
Would you like to know how VRA fits into your spraying strategy? Explore the possibilities of WEED-IT and discover how variable spray output can give you more control over your application in the field.
