Abstract
BackgroundNitrogen (N) as a key input for crop production has adverse effects on the environment through emissions of reactive nitrogen. Less than 20% of the fertiliser nitrogen applied to agricultural land is actually consumed by humans in meat. Given this situation, nitrogen budgets have been introduced to quantify potential losses into the environment, to raise awareness in nutrient management, and to enforce and monitor nutrient mitigation measures. The surplus of the N soil surface budget has been used for many years for the assessment of potentially water pollution with nitrate from agriculture.ResultsFor the 402 districts in Germany, nitrogen soil surface budgets were calculated for the time series 1995 to 2017. For the first time, biogas production in agriculture and the transfer of manure between districts were included in the budget. Averaged for all districts, the recent N supply to the utilised agricultural area (UAA) totals 227 kg N ha−1 UAA (mean 2015–2017), among them 104 kg N ha−1 UAA mineral fertiliser, 59 kg N ha−1 UAA manure, 33 kg N ha−1 UAA digestate, 14 kg N ha−1 UAA from gross atmospheric deposition, 13 kg N ha−1 UAA biological N fixation, and 1 kg N ha−1 UAA from seed and planting material. The withdrawal with harvested products accounts for 149 kg N ha−1 UAA, resulting in an N soil surface budget surplus of 77 kg N ha−1 UAA. The N surpluses per district (mean 2015–2017) vary considerably between 26 and 162 kg N ha−1 UAA and the nitrogen use efficiency of crop production ranges from 0.53 to 0.79 in the districts. The N surplus in Germany as a whole has remained nearly constant since 1995, but the regional distribution has changed significantly. The N surplus has decreased in the arable farming regions, but increased in the districts with high livestock density. Some of this surplus, however, is relocated to other districts through the transfer of manure.ConclusionsThe 23-year time series forms a reliable basis for further interpretation of N soil surface surplus in Germany. Agri-environmental programmes such as the limitation of the N surplus through the Fertiliser Ordinance and the promotion of biogas production have a clear effect on the N surplus in Germany as a whole and its regional distribution.
Highlights
Nitrogen (N) as a key input for crop production has adverse effects on the environment through emissions of reactive nitrogen
We present the methodology and the results of N soil surface budget calculation for the district administrative units (Nomenclature des unités territoriales statistiques, NUTS 3 level, “Kreise”) in Germany for the time series 1995 to 2017
At present, the largest input of 104 kg N ha−1 a−1 is made with mineral fertiliser followed by organic fertilisers from livestock and biogas production with nearly 89 kg N ha−1 a−1 (Table 2)
Summary
Nitrogen (N) as a key input for crop production has adverse effects on the environment through emissions of reactive nitrogen. Less than 20% of the fertiliser nitrogen applied to agricultural land is consumed by humans in meat Given this situation, nitrogen budgets have been introduced to quantify potential losses into the environment, to raise awareness in nutrient management, and to enforce and monitor nutrient mitigation measures. It is a big challenge to produce enough food for the growing global population while at the same time minimising the emission of reactive N to the environment Given this situation, agriculture N budgets have been introduced to clarify the nutrient flows, to quantify the potential N losses, to indicate the pressure on environmental media, to raise awareness in nutrient management, and to enforce and monitor nutrient mitigation regulations in practice [5]. The reduction in N budget surplus and in groundwater nitrate concentration in Denmark illustrates the success that can be achieved if effective measures are taken [9]
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