A good way to improve the management of nitrogen fertilisation in potato crops is to split the total nitrogen dose recommended at the start of the season, followed by an adaptation of the amount of nitrogen supplement to be added during vegetation development, by determining the nitrogen status of the crop. Sentinel-2 satellites, from the Copernicus programme, allow the use of free images with very interesting spatial (ten metres) and temporal (five days) resolutions to monitor nitrogen status at the plot scale. The STARGATE project tested the combined use of Sentinel-2 data and meteorological data (degree days) to assess this nitrogen status. More specifically, this assessment concerned biomass (tonnes of dry matter per hectare), nitrogen content (% nitrogen in plants), nitrogen absorbed (kg of nitrogen per hectare absorbed by plants) and finally the determination of the index of nitrogen nutrition (INN).
The results of the study demonstrate that these different parameters can be evaluated with good accuracy and are favourable to a methodology using biomass and absorbed nitrogen to determine the INN. Assessment of nitrogen content is therefore not necessary. This study forms the basis of a nitrogen recommendation tool at plot scale intended for farmers.
In practice, the farmer splits the nitrogen supply by applying 70% of a dose recommended at planting. During the development of the vegetation (between 20 and 50 days after emergence), the INN makes it possible to determine if the crop is nitrogen deficient, and, if it is, when it is necessary to apply the nitrogen supplement. Then the estimate of the nitrogen absorbed makes it possible to determine, on the basis of a target yield, the quantity of nitrogen to be supplied for a second application.
The study was based on data collected as part of the BELCAM project over 3 consecutive years (2017-2019). The developed methodology is being integrated on the BELCAM platform.
BELSPO, SR/42/203 – STARGATE agreement