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In the Nitrate Vulnerable Zones farmers are required to implement measures to reduce the nitrogen (N) surplus. Nevertheless, in some cases the status of the water bodies show that the effect of these measures remains insufficient despite the global decrease in N surpluses. The present work aims to contribute with a method that produces an appropriate indicator for the N mitigation measures effectiveness for reducing groundwater nitrate pollution. The Global Risk Index (GRI) results from overlaying the agricultural N surplus hazard and aquifer vulnerability. It includes both irrigation activity and precipitation contribution to water recharge calculated at the municipality level. It integrates a range of regional datasets combined with monitored nitrate (NO3−) concentrations in groundwater under a GIS framework. Results show that the pollution status of the Tagus Vulnerable Zone (TVZ) aquifers has been aggravating in spite of the overall reduction in the N surpluses that resulted from the implementation of the Nitrates Directive measures. Twelve years after the TVZ designation, the GRI indicates high and moderate NO3- pollution risk, respectively in 33 % and 66 % of the territory. Scenario analysis indicates the potential of targeted measures for ending high risk areas and reducing moderate risk areas to 13 %. This supports that N mitigation measures must be reformulated and spatially targeted according to site specific hazards and vulnerabilities.

Agricultural activities are responsible for most of the nitrogen (N) inputs that degrade water quality. To elucidate the drivers leading to N pressures on water, we examined the resulting state of surface waters in terms of N concentrations, the impact of this on water quality status and policy responses to these constraints across different climatic and management conditions. Portugal and Denmark were chosen as contrasting case studies for the Driver-Pressure-State-Impact-Response (DPSIR) analysis. Our results showed reductions of 39% and 25% in the use of mineral fertilizer in Portugal and Denmark, respectively, between 2000 and 2010. The N surplus in Portugal varied between 15 and 30 kg N ha−1 between 1995 and 2015. In Denmark, in 2015, this amount was 70 kg N ha−1, representing a 53% decrease from the 1990 value. The average amount of total N discharged to surface waters was 7 kg ha−1 for mainland Portugal in 2015 and 14.6 kg ha−1 for Denmark in 2014. These reductions in the N surplus were attributed to historical policies aimed at N pressure abatement. In Denmark, N losses are expected to decline further through the continuation or improvement of existing national action plans. In Portugal, they are expected to decline further due to the expansion of Nitrate Vulnerable Zones and the introduction of targeted policies aimed at improving N use efficiency and reducing losses to water.

Although environmental impacts of biochar are well characterized, impacts on soil quality, nutrient availability and crop productivity, still remain a challenge due to the diverse response of different soil types to different types of biochar, namely those obtained at low temperature. The impact of an alkaline woody biochar (two doses 5% and 10%) obtained at 280°C, on soil enzyme activity, soil microbial respiration rate, mineral nitrogen (N) availability and ammonia volatilization was studied in one conventionally and one organically managed soils, with and without the addition of urea or composted farmyard manure. Biochar additions had different effects on soil enzyme activity in both soils, suggesting lower decomposing microbial activity processes promoted by biochar. Both soils showed a similar decreasing trend regarding soil respiration rates for all treatments, and significant relationships were observed between the treatments with different rates of applied biochar, but not constant for the entire incubation period. Urea application increased soil mineral N concentrations, especially nitrate concentrations when biochar was applied as well. Biochar decreased ammonia volatilization from conventionally managed soil fertilized with urea, but did not have a significant effect when compost was added to the organically managed soil. Biochar altered microbial behavior in soil, and was affected by previous soil management. So, the impact of biochar produced at low temperatures on soil biological processes is similar to those obtained at high temperature, thus proving that there is no need to increase the energy expenditure to produce biochar, to obtain a good product.