According to our experience gained from fertiliser consultancy, determining the correct timing and quantity of N applications for cereals (for the second, third and possibly fourth application) and winter oilseed rape (autumn fertilisation) remains a considerable problem in practice. As a result, the N requirement of the plant is not covered at the right time with the right quantities. In the past (before the current Fertiliser Ordinance), attempts were made to compensate for this with high N fertiliser quantities, resulting in poor N efficiency.

N monitoring is a tried and tested method for determining the right time and the right amount of N application in cereals. This involves measuring the N nutritional status of the crops in a field at a defined point every two days (N tester or rapid nitrate test) and thus mapping the N dynamics of the crop over time. The evaluation of these records makes it possible to determine the correct fertilisation time and helps to determine the correct amount of fertiliser (adjusted according to german fertiliser ordinance).

Unfortunately, in practice, although N-testers or other tools have been procured, N-monitoring is often not used continuously, not across the board and sometimes even incorrectly. The reasons for this are varied, cannot really be influenced and range from time expenditure to logistics and qualification problems up to ignoring and doubting the test results. In winter oilseed rape, N monitoring is not possible at all as the N concentration in the leaves of a plant varies greatly and therefore no reliable values of the N nutritional status can be recorded.

This is not practical, especially in light of the current Fertiliser Ordinance and the implementation of the WFD. In addition to the resulting inappropriate conventional fertilisation, the agronomic calibration of plant sensors (YARA N-Sensor, ISARIA, Greenseeker, etc.) for site-specific N fertilisation is therefore not always optimal and could be significantly improved.

The aim of the project is to create a farm- and region-specific N fertilisation advisory system as software that records information relevant to crop production (e.g. N uptake, soil moisture, soil temperature, etc.) using daily measurements from rugged, simple field sensor stations and to derive field-, farm- and region-specific parameters for more qualified, adapted N fertilisation. This alleviates the operational problems of N measurement mentioned in the problem description and opens up further possibilities for N consulting for organisations, consultants and regions.

Using several field sensor stations can make it easier to fertilise the right amount of N at the right time. For a region (several farms with stations), this provides the opportunity to make qualified statements about the N status of the crops.

The EXAgT Observatory since 2022


  • Monitoring the condition of the crops by measuring the N uptake twice a day.
  • Collecting weather data from a nearby weather station, e.g. from the DWD or from our partner Pessl Instruments.
  • Visualisation of the temporal development of the data and transmission by e-mail to the farmer/advisor.
  • Based on this information, the farmer makes the decisions regarding adapted N fertilization (time and amount of application), an automation of the decision-making process is prepared and possible.
2022 measurements
Drone flight with multispectral sensor

Regarding the EIP Agri project

Our EIP-AGRI project “Development of a farm- and region-specific N-fertilisation advisory system based on stationary field sensor stations and drones to derive an adapted N-fertilisation in accordance with the Water Framework Directive (WFD) and the new Fertiliser Ordinance (DüV)” has a duration of three years (2018 – 2021) and is funded by the Saxon State Office for Environment, Agriculture and Geology. The project is in accordance with the directive of the Saxon State Ministry of the Environment and Agriculture for the promotion of agriculture, European Innovation Partnerships (EiP AGRI) and knowledge transfer including demonstration projects within the framework of the development programme for rural areas in the Free State of Saxony (Funding Directive Agriculture, Innovation, Knowledge Transfer Directive LiW/2014). Part: European Innovation Partnership “Agricultural Productivity and Sustainability” (EIP AGRI) of 15 December 2014.