Using Sensors to Better Adapt Nitrogen Fertilisation to Plants and Soils

European Journal of Agronomy 34, 126462, 2022

To ensure a good harvest while protecting the environment, a nitrogen surplus must be avoided. Agroscope is investigating how the application of nitrogen fertiliser can be better adapted to soil replenishment and the needs of the plants.

Commercial sensor systems such as tractor-, drone- and satellite-based applications are already available at present for targeted nitrogen fertilisation. In order for these systems to be used effectively and efficiently in agriculture, however, further development under practical conditions is essential. In future, satellite-based applications could be used for site-adapted fertilisation, supported by drones and/or tractor-based systems according to need.

Adapting fertiliser application – protecting the soil, water and air

With nitrogen fertilisation, it is important to get the dosage right. This means adjusting the amount of fertiliser both temporally and spatially to the needs of the plants whilst bearing in mind the soil nitrogen supply. Doing this can prevent excess nitrogen from finding its way into the environment, where it can pollute the groundwater as a nitrate or exacerbate the greenhouse effect as nitrous oxide.

To obtain an indicator for the quantity of plant-available nitrogen, the soil-water nitrate content was measured in a winter wheat study. For this, Agroscope experts used suction cups and sensors embedded in arable soil at a depth of between 15 and 45 cm. Because this indicator is not sufficient on its own to determine plant nitrogen uptake, however, the researchers also concurrently analysed multispectral images from a camera drone as well as plant samples in order to measure plant nitrogen content. All these data were linked together to determine the connection between the dynamic processes of soil nitrogen replenishment and N uptake in the plants.

Measuring plant nitrogen uptake with drones

During the growing season, the plants largely absorb the available nitrate in the soil water, but the supply is also replenished in the soil. Weather conditions, for example if water becomes scarce, play a major role here.  The results showed that it is possible to measure plant nitrogen uptake with calibrated multispectral images. Using these in combination with calculation models that determine the nitrogen replenishment in the soil, nitrogen fertilisers can be dosed more precisely, thereby reducing surpluses. 

Link to the video

Digitalisation Enables Targeted Fertilising