AgroGreen-SUDOE Visualisation Tool

This visualisation tool is an invitation to a journey. A journey through the agricultural systems of the SUDOE territory (Spain, Portugal and south-west France), with a special focus on the Garonne and Tagus river basins.

The journey is divided into several stages, initially looking at the system as a whole, with an overview of the importance of nitrogen as a key crop nutrient and a source of multiple environmental problems associated with agricultural production. This will be followed by stops at key points in the system, looking closer at the nitrogen flows that drive the system, some alternative management options, the agricultural production obtained, and the air and water pollution we can expect.

 The journey begins 

The farming systems of the SUDOE territory cover a cropland area of more than 20 million hectares. Cereal crops such as maize, wheat and rice, horticultural crops, industrial crops such as sugar beet and, finally, woody crops such as olive groves and vines stand out. These are crops which, in addition to sustaining the economy of many people, make up the landscape of this territory.

Agricultural activities ensure quality food and raw materials. However, some of these activities can also give rise to environmental problems such as the emission of greenhouse gases and the release of pollutants into water and the atmosphere, thus putting the health of ecosystems and people at risk.

Since the start of its activities in 2020, the AgroGreen-SUDOE project has sought to co-design, together with the main actors involved (farmers, decision-makers, and researchers), alternative crop management strategies that lead to lower environmental impacts and, consequently, allow us to move towards more sustainable agri-food systems. The aim is to explore alternatives and possible changes in the way we fertilise, irrigate and even eat. These changes seek to reduce the possible environmental impacts linked to agricultural production, but without neglecting their effects on agricultural productivity and the economic benefits for farmers. Showing these results is the purpose of this journey.

Agricultural systems are particularly sensitive to climate change. These effects can be particularly pernicious in areas with a Mediterranean climate, such as the SUDOE territory. In these areas, the proportion of dry years could increase, as well as the intensity of droughts. Furthermore, the way in which agricultural production can affect the environment also depends on changes in climate. To be sensitive to this, we have made all of our analyses for a wet and a dry year.

Nitrogen is an essential element for life as it is part of the proteins and DNA of all living things. Plants need this nutrient to develop normally. Similarly, animals need to ingest an adequate amount of protein, rich in nitrogen, including all the essential amino acids. For this reason, the availability of nitrogen is essential in food production.

GRAFS stands for "Generalised Representation of Agri-Food Systems". It is a tool, developed by the METIS laboratory of the Sorbonne University, quantifies nitrogen flows between crops, livestock, humans and the natural environment. As you can see in the figure below, the four main components are: cropland, including arable crops in rotation, some of which are nitrogen-fixing legume crops, and permanent crops such as olives and vines; grassland, permanent or semi-natural, for use as livestock feed; livestock systems; and human population centres, including their food consumption. The main nitrogen inputs to crops include synthetic and manure fertilisation, other forms of organic fertilisation such as sewage sludge, atmospheric N deposition, and N fixation by legumes.

In the alternative scenarios explored in the AgroGreen-SUDOE project we have focused on changes in fertilisation practices, more efficient irrigation technology, increased nitrogen fixation by legumes, and finally changes in human diet towards options close to the Mediterranean diet. These changes lead, in all the cases studied, to lower environmental impacts in the form of pollutant emissions into the atmosphere and water.

In the AgroGreen-SUDOE project we have taken as a starting point the recent reality of farming systems in 2017 (dry) and 2018 (wet). Based on this reference situation, which we call the "baseline scenario", we have compared changes in crop management with a focus on fertilisation, irrigation and the presence of legumes in the rotations. These alternative scenarios are the result of co-creation with the different actors in the territory and can lead to lower environmental impacts linked to agricultural production.

AgroGreen-SUDOE scenario. Within synthetic fertilisers, in this scenario we propose not to use urea, as it is the fertiliser with the highest ammonia emissions generated after its application on the surface of agricultural soils. All synthetic fertilisation is done with calcium ammonium nitrate (CAN) and irrigation water is applied using drip irrigation. In addition, all manures are incorporated into the soil within 24 hours after application. In this scenario, green maize is replaced by alfalfa, aiming for an increase in biological nitrogen fixation. The reduction in nitrogen application by eliminating the use of urea is compensated by increased efficiency and biologically fixed nitrogen, so that yields in this scenario become similar to those of the base scenario.

In the "Extensification" scenario, a 50% reduction of synthetic nitrogen inputs is realised, following the recommendation of the EU farm to fork initiative, the crop and fertiliser mix is the same as in the baseline scenario. In addition, a transition towards a Mediterranean diet is proposed, with a 30% reduction in animal protein intake.

Finally, as a combination of the two previous scenarios, the "AgroGreen+Extensification" assumes of reducing synthetic nitrogen inputs by 50%, replacing the rest of the synthetic N with CAN, immediate incorporation of manure into the soil, replacing green maize with alfalfa, and transition to a Mediterranean diet.

In the remainder of the journey (a few stops to go), we will compare the impact on different pollutants and greenhouse gases of applying one scenario or the other.

Next, we show the GRAFS for the entire SUDOE territory in a dry year, first, and a humid one below. In both cases you can compare, by clicking on the arrow on the right, the result of the base scenario with the alternative scenarios evaluated in AgroGreen-SUDOE. In addition to the results for the SUDOE space as a whole, you can find the detailed GRAFS for each province of the territory below.

Nitrogen first enters the cropping systems mainly through synthetic fertilisers and also from the fixation of legumes such as soybeans, lentils or alfalfa. Once the crop is produced, it can be used for direct human consumption or as livestock feed. The majority of the nitrogen consumed by animals ends up in manure, which apart for some losses is then used as fertiliser for crops. In some of our alternative management scenarios we have envisaged a reduction in fertilisation, which can lead to lower crop yields. In the map below you can see, for each scenario, the reduction in synthetic fertiliser input, the impact on crop yields and the economic impact compared to the base scenario.

Throughout the journey of nitrogen, from the time it is applied to crops until it reaches our plates in the form of plant or animal protein, there are many losses to the environment that pose a threat to the environment and a waste of the fertiliser resource.

One of the most important loss pathways is ammonia that is emitted into the atmosphere. This ammonia reacts with other compounds in the air, resulting in suspended particles that affect human health when inhaled and ecosystem health when deposited on the surface of leaves or on the soil. Another loss pathway foris leaching of nitrate to deep soil layers and groundwater or surface water. This is the main cause of serious environmental problems such as eutrophication of river and coastal waters, which can cause harmful algal blooms and loss of biodiversity, as well as nitrate contamination of aquifers. Contamination of aquifers is of particular concern in Mediterranean regions where drinking water supply is sometimes very limited. A third loss pathway, quantitatively smaller but environmentally important, is nitrogen emitted in the form of nitrous oxide, which is a potent greenhouse gas.

Ammonia emitted into the atmosphere can react with other compounds and lead to the formation of suspended particulate matter (PM). The microscopic PM and ammonia itself cause significant impacts on public health and ecosystems. This is why we focus on the concentration of these pollutants in the atmosphere. The chemical transport model CHIMERE, widely used in international scientific studies, has been the tool used to evaluate the reductions in pollutant concentrations achieved by implementing the different scenarios.

This stop focuses on the potential contamination of water by compounds such as nitrates, which are responsible for environmental problems such as eutrophication and public health risks. The presence of nitrates in groundwater and surface water in high concentrations led, in the 1990s, to the development of specific European regulations to mitigate them. The Water Framework Directive led to the declaration of areas vulnerable to nitrate pollution in the EU territory, with 50 mg of N per litre being the established limit.

The results shown are derived from the estimation of diffuse sources of nitrogen —those "sources of water pollution without a specific point of origin such as those linked to agricultural production"— based on the net nitrogen surplus calculated at the provincial scale (NUTS2) by the GRAFS model for cropland, permanent crops and grassland. This information was taken to the scale of the Garonne river basin in France and Tagus river basin in Spain and Portugal. N exceedances were transformed into nitrate concentrations in agricultural areas, considering long-term runoff. Diffuse sources of nitrogen were calculated at the river basin scale, coupling these annual mean nitrate concentrations with the water fluxes (groundwater and groundwater) simulated by the SWAT model.

In addition to the nitrate concentration in the cultivated areas of the catchments under study in the SUDOE territory, we calculated the nitrate concentration within the watercourses as a result of a cascade of processes affecting nitrogen fluxes from agricultural soils, through riparian zones and also along the drainage network. For this purpose, the pyNuts-Riverstrahler model was used. This river model takes into account a combination of natural constraints (hydromorphological, climatic, etc.) and constraints linked to human activities (sewage treatment plants, diffuse agricultural pollution, construction of reservoirs). For nitrogen, the aquatic processes simulated are mainly denitrification (which occurs in riverside wetlands, but also in the deep parts of dams-reservoirs generally rich in organic matter) and the nitrification of ammonium discharged into aquatic systems by wastewater treatment plants (and which can lead to the production of nitrite and N2O). The impacts of reservoir dams are taken into account by the possible retention of nitrogen calculated from the characteristics of the dams and the flows of the regulated dams.

We have focused our work on the Tagus and Garonne hydrographic basins as they are the most important within the SUDOE space studied in the project. Below we show the impact of the different scenarios on water pollution by nitrates in the area of ​​these basins, both in their territory and in the river currents that confirm them.

Over the past three years, AgroGreen-SUDOE has allowed us to be in places with people we never expected. On a day-to-day basis, everything seems very ordinary and normal, but when you stop for a moment and think back, you realise what a beautiful journey it has been: Madrid, San Fernando de Henares, Coruche, Lisbon, Toulouse, Bordeaux, Donostia, and all the places where we once stopped to rest a little, to have a coffee, to talk and laugh, by the side of the road.  The following texts  not only tell the scientific part and some of the most important activities that have taken place around AgroGreen-SUDOE in the last years, but also want to be a small tribute to the people who made this beautiful project possible. To them, thank you, merci, gracias, obrigado.

In close and synergic collaboration with farmers in the area, we have sought to create a  nutrient calculator  as a tool to help them make decisions regarding fertilisation, taking into account the possible environmental impacts linked to this crop management practice. This tool also serves as a field notebook in that it allows fertilisation data to be recorded for each farm.

 _{Contact:    ALBERTO SANZ COBEÑA (Coord.) | agrogreen.ceigram@upm.es    CEIGRAM  | C/Senda del rey 13, 28040 MADRID} 

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