A free online tool to calculate three nitrogen-related indicators for farming systems

Reactive nitrogen (N) is a key agricultural input, essential for crop growth and production, but excess N in the environment causes problems for human and ecological health. One of the most promising solutions for reducing environmental impacts of excess N levels and feeding a growing population is to improve N efficiency of farming systems i.e., increase the ratio of their N output to N input. Assessing promising solutions involves calculating N efficiency, which is not trivial. For this reason, a free online tool was developed - the SyNE calculator, https://www.nefficiencycalculator.fr/en/ - to allow farmers, farm advisors, researchers, and policy makers to calculate three N-related indicators of farming systems: SyNE, an N efficiency indicator; SyNB, an N balance indicator; and RNE, a relative N efficiency indicator. After entering information about a farming system, the SyNE calculator produces two main outputs: first, values of the three indicators (SyNE, SyNB, and RNE) and those of related variables (N inputs, N losses during production and transport of inputs, N outputs, and change in soil N); second, a downloadable diagram showing these values. The main advantages of this tool are that it (i) simplifies N indicator calculation, using the same scientific framework for all farming systems, and (ii) includes many reference values that are difficult to obtain (e.g., N losses during production and transport of inputs). Furthermore, this tool allows advanced users to modify the values and equations used to calculate the three N-related indicators. The SyNE calculator is currently available for farms producing dairy cattle, beef cattle, and field crops; in the near future, it will be available for farms producing pigs and broilers. If used, this online tool will contribute to the development of N efficiency evaluation by farmers, farm advisors, and researchers, which may result in improved agricultural N management practices.