Atfarm’s agronomic calibration based on the N-Sensors target rate algorithm.
Atfarm uses data from Sentinel 2 satellites to calculate a vegetation index which we call N-Sensor biomass index. Based on more than two decades of research at Yara’s research center Hanninghof in Dülmen, robust calibrations for this index were developed to estimate the nitrogen uptake of a crop canopy by its spectral reflectance. This was done to develop the N-Sensor and 20 seasons in the market show high precision of these calibration curves.
In Atfarm we run these, and the follow-up calculations per pixel of the selected field on a 20 by 20-meter grid (note: on very large fields, grid size can vary).
After estimating the nitrogen uptake of the canopy, the algorithm addresses higher N rates to areas with lower N uptake, and lower rates for areas with higher N uptake. This is best used early in the season when the crop still can compensate growth differences, e.g. through promotion of tillering.
Biomass Cut-Off: For the agronomic calibration algorithm, a biomass cutoff is implemented. This 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.
Protein dressing: For the last dressing, at later growth stages (in cereals from GS37 – flag leaf visible onwards), we recommend using the Protein dressing function. This algorithm addresses more N to areas with higher biomass. This ensures consistent protein concentrations and prevent protein dilution in high yielding areas.
Leveling versus boosting algorithm for crops & regions where we don’t have a N-Sensor calibration:
Leveling: The leveling algorithm addresses higher N rates to areas with lower biomass, and lower rates for areas with higher biomass. This is best used if nitrogen is the growth limiting factor and you want to make sure all areas in your field have enough nitrogen.
Boosting: The boosting algorithm addresses higher N rates to areas with higher biomass, and lower N rates for areas with lower biomass.
- This is best used if other factors (e.g. water availability) limit your crop growth and yield potential.
- It is also recommended for protein dressings to assure homogeneous protein levels across your fields.