Blicher-Mathiesen, G., Olesen, J.E. & Jung-Madsen, S. (red). 2020. Opdatering af baseline 2021. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 140 s. - Teknisk rapport nr. 162
http://dce2.au.dk/pub/TR162.pdf
In the beginning of 2019, The Danish Environmental Protection Agency (MST) commissioned an update of the baseline prepared for the 2nd generation of river basin management ("Establishing baseline 2021" from 2014), which was subsequently re-evaluated in 2015 (Reassessment of baseline, Jensen et al., 2016) prior to the adoption of the Food and agriculture package. In this context, the term baseline covers the effect of measures already adopted (instruments etc.) and other developments in agriculture that may affect the loss of nitrogen from arable land. This report evaluates the conditions and assumptions made in the "Reassessment of baseline" from 2016 and, based on this, the baseline effect was updated overall for the six-year period 2013-2017/2018 as were the expectations for the effect for 2013-2021. Measures adopted in the Food and agriculture package in 2015 to counteract the effects of phasing out the sub-optimal fertilisation standards, including MFO, wetland projects, additional catch crops and their alternatives, etc. are not included in the update, nor were they included in the Reassessment of baseline.
The present report estimates an overall change in nitrogen loss (nitrate leaching) from the root zone in 2021, which varies between an additional leaching of 5,310 tonnes N/year and a reduction in leaching of 2,930 tonnes N/year, corresponding to an average additional leaching of approx. 1,190 tonnes/year compared to the reference year 2012. However, the 2018 status shows total additional leaching between 3,300-8,840 tonnes N/year, on average approximately 5,970 tonnes N/year.
The fact that a significant decrease in additional leaching has not yet been seen up to the year 2018 is mainly due to the fact that the expected reduction in atmospheric deposition resulting from all EU countries having committed themselves to reducing nitrogen emissions to the air has not yet occurred. As the reduction requirements are statutory, it is assumed in this report that the countries will reach the established emission ceilings.
In the Reassessment of baseline, the overall baseline effect was estimated to be in the range between additional nitrogen leaching of 4,300 tonnes N/year and reduction in nitrogen leaching of 350 tonnes N/year; additional leaching of 1,975 tonnes N/year on average. This means that in the current update, the overall effect is estimated to be approximately 785 tonnes less than previously estimated in the Reassessment of baseline.
The reason for this is notably that the present report has estimated a greater positive effect of ecology as a result of larger areas with organic farming as well as a lower estimated effect of increasing fertiliser standards to the economic optimum. The decreased effect of changing fertiliser standards is justified by the new calculation in this report involving more realistic crop distribution and taking into account the fact that the fertiliser standards are not fully exploited. However, it is extremely difficult to accurately distinguish the effects of the decline in arable land, norm changes from sub-optimal to economically optimal nitrogen norms and the annual increase in the economically optimum norm, change in crop distribution and yield trend.
All in all, this update of the baseline calculation predicts a lower level of nitrogen leaching in 2021 than was expected in the Reassessment of baseline in 2015. However, this estimate is highly dependent on the evolution of the atmospheric deposition and whether the forecasts for the emissions developments prevail, including the EU countries being able to comply with the agreed upon emission ceilings for atmospheric nitrogen emissions.
Overall, this update of baseline 2021 shows that consumption of commercial fertilizers and leaching of nitrogen will be reduced due to decline in cultivated area and increased share of organic farming. In addition, the expected decline in atmospheric deposition will also reduce leaching. Conversely, baseline elements such as increasing yields, combined with increased fertilizer norms and additional fertilizers, allowed by going from below- to economically optimal norms, will increase the use of commercial fertilizers and increase leaching.
The effect of the baseline elements up to 2018 therefore shows increased nitrogen leaching, among other things because the expected reduction in atmospheric deposition has not yet occurred and because baseline 2021 does not include the effect of targeted catch crops, MFO etc.. The last mentioned mitigation elements contribute to compensate for the increased leaching caused by the use of additional fertilizers to meet the economically optimal nitrogen standards.
Looking at the period 2012-2015, which is the period before consumption of the additional fertilizer by going from below to economically optimal norms, it can be difficult to see the positive effect in the trend of the nitrogen load to coastal waters of the two baseline elements decline in the cultivated area and increased proportion of organic cultivation. This may be because by a limited size effect of the two measures, which can be overshadowed by large year-to-year variation in, among other things precipitation and temperature that may counteract or even temporary increased the nitrogen load, as shown for the years 2012-2015. In addition, delays in nitrogen turnover in the agricultural soil and in water transport pathways from the fields to coastal waters can be significant. Regional estimates of the flow-weighted total N and nitrate concentration in the discharged water calculated for catchments with gauging stations show that the year-to-year variation is large in the two regions of Funen and Zealand, and that changes in the flow-weighted concentrations therefore should be seen over a number of years, if the effect of measures on nitrogen load into coastal waters should be evaluated
