What is Variable Rate Application (VRA)?
The progress of technology is also reflected in agriculture. Precision fertilization is made possible using Variable Rate Application (VRA). With the VRA technology the application rate is precisely adjusted to a location or to the characteristics of an area. This saves materials and costs and better protects our environment.
What type of VRA does Atfarm provide? What differs Atfarm from other tools?
Atfarm uses data from Sentinel-2 satellites to calculate a vegetation index. With the regularly updated satellite images you can create VRA maps for nitrogen for your fields. The VRA maps in Atfarm are based on Yara's N-Sensor target rate algorithm, which makes Atfarm special.
Yara's N-Sensor is a tractor-mounted remote sensing device, that determines a nitrogen demand by measuring the crop's light reflectance. The first N-Sensor (Classic) was introduced in 1999 for use on cereals and more than 250 trials have been carried out until 2010 to refine its performance and to add new programs. Atfarm uses this crop and region-specific calibrations to create the VRA maps for nitrogen based on satellite images.
Nearly all other offered tools use the NDVI (Normalized Difference Vegetation Index) based on red and near-infrared radiation - a technology older than 50 years - and can therefore only detect differences in early growth stages. From shoot development of the plants, this index saturates very rapidly and loses it's informative value.
So far, only the N-Sensor Index developed by Yara can make biomass differences visible during and after shooting and create precise VRA maps for these growth stages.
Which VRA strategies can I select in Atfarm?
After Atfarm's algorithm calculated the nitrogen uptake of the canopy, you can select two strategies:
The Levelling strategy addresses higher nitrogen rates to areas with lower biomass/nitrogen uptake and lower nitrogen rates for areas with higher biomass/nitrogen uptake. This is best used when nitrogen is the growth limiting factor and you want to ensure, that all areas in your field contain enough nitrogen. This strategy is best used early in the season when the crop can still compensate growth differences e. g. through promotion of tillering.
The Boosting strategy addresses higher nitrogen rates to areas with higher biomass/nitrogen uptake and lower nitrogen rates for areas with lower biomass/nitrogen uptake. This is best used when other factors (e. g. water availability) limit your crop growth and yield potential. The Biomass Cut-Off instructs the redistribution algorithm to cut back to the minimum application rate when the biomass measurement falls below a certain level. This ensures nitrogen is not wasted on areas of the field which are not likely to yield due to crop damage, waterlogging etc. Rather than applying very high rates of nitrogen due to the low biomass values it is assumed that the crop is uneconomical to treat and therefore cuts right back.
It's also recommended to use the Boosting strategy for protein dressings to assure consistent protein concentrations and to prevent protein dilution in high yielding areas. The protein dressing is intended for the last dressing at later growth stages (in cereals from GS37 – flag leaf visible onwards).
When creating a VRA map for your field, you can choose the Boosting algorithm only for late growth stages. If you want to choose the Boosting method for earlier growth stages, you can create the VRA map manually and then choose the Boosting method.