20 Dec 2019

Interview with Prof. Miguel Quemada, Technical University of Madrid

EU Nitrogen Expert Panel showcased its latest publication “Exploring nitrogen indicators of farm performance among farm types across several European case studies” at the 2019 IFS Agronomic Conference written  by Prof. Miguel Quemada et al. on behalf of the EU Nitrogen Expert Panel (EU NEP).  The report demonstrates how the economic and environmental performance of a specific farm regarding different nitrogen indicators is closely related to its type and its management.

In this interview Prof. Miguel Quemada explains the scope of the study as well as its main findings and impacts on scientific discussion about nitrogen management.

  1. What is the new scientific publication of the EUNEP about?

The new publication is about the application of nitrogen indicators to analyze the farm performance in several European countries. Nitrogen indicators are key for characterizing farm performance, because of the role of N in food production and environmental quality. Nitrogen is essential for life and is needed in large quantities for plants and animals, however, excess N produces pollution of water and air and is a threat to the environment. Because of that, four years ago the European N expert Pannel proposed a set of N indicators easy-to-use and robust that can be applied to agriculture and food production systems.

The indicators proposed were ‘nitrogen use efficiency’ calculated as the ratio between the N output and the N input of a system. It is an indicator of resource efficiency.

The N surplus that is calculated as the difference between the N input and the N output, and it is an indicator of the potential environmental impact of the system.

Finally, the N output is an indicator of the system productivity.

The goal of our study was to test these approach in actual farms. So we collected information from more than 1200 farms from 6 European countries and applied the N indicators with the aim of understanding differences in N performance between farm types. We also wanted to derive information for target values, and to identify the factors that influence these indicators.

  1. What are the main findings?

The main achievement of this work is the development of a systematic monitoring protocol of N balance at a farm level. A Guidance document was developed that clearly defined how to account for the different components of the N balance, allowing comparison among the indicators and providing a two dimensional framework to analyze farm performance.

The main findings are that N indicators were related to farm type and management. Arable farms had the highest N use efficiency and N output and the lowest N surplus. In contrast, livestock farms had the lowest N use efficiency and the highest N surplus. Mixed farms, with crop and livestock, had values between the specialized farms. As an example, mean NUE was 61% for arable farms, 28% for dairy and 43% for pig farms. With respect to the N surplus, arable farms had a mean N surplus of 68 kg N/ha whereas dairy farms had 155 kg N/ha.

This work also highlights the importance of externalization on the N indicators of animal farms. Externalization means not accounting for N losses involved either in the production of the feed imported into the farm, or the end use of manure exported out of the farm; and externalization is a fake-way of increasing N use efficiency in farms that are not linked to the territory. We estimated the effect of externalization by recalculating the N inputs with adjusting factors and showed that for instance the mean NUE for dairy farms decreased from 28% before externalization to 19% after, and the N surplus increased from 155 kg N/ha before to 268 kg N/ha after.

  1. Which impact can this paper have on scientific discussions about nitrogen management?

The two dimensional framework proposed for plotting the farms may have a large impact on the scientific discussion. A population of farms is plotted in a Ninput/Noutput framework together with the N indicators; in such a way that a ‘characteristic operation space’ is defined for any farm population, depending on the farm type or region. This space can be used to analyze the effect of environmental policy implementation or to assess the location of a farm relatively to the rest of the farm population. Farms outside the characteristic operating space should change production practices to move into the space. Depending on their current situation, this can be done by increasing N inputs, that means by intensification, or by reducing N inputs, that means by an extensification pathway. In some cases, additional strategies may also be necessary to increase agro-environmental performance of the farms that should follow sustainable intensification pathways. With the two-dimensional framework we can also identify situations with a potential risk of soil mining. That is, farms that export more N than provided with N inputs with the potential of mining soil N and also C, diminishing soil fertility and compromising long-term sustainability.

Another relevant impact expected on the scientific discussion is highlighting what the N input should involved in animal farms. The N input should account for the N required to produce the imported feed or concentrates instead of the actual N imported in the feed, and for N losses associated with manure export or management.

Finally, the ambition of this paper is to contribute to improving efficient N use in food production and to decrease the environmental impact of our agricultural systems. The proposed indicators are suitable for setting realistic targets and monitoring of progress in reaching these goals.

The paper, “Exploring nitrogen indicators of farm performance among farm types across several European case studies” can be downloaded here.