The assessment of nitrogen emissions from manure management and their mitigation adopting Short Rotation Coppice Crops

Excess of reactive nitrogen is a matter of great concern, especially in developed coun-tries. Reactive nitrogen can be dangerous to human health, for the environment (eu-trophication, acidification of soils, emissions) and also for agriculture, because of the economic burden related with the disposal of manure, in the past a valuable nutrient, nowadays considered only a problem. Agriculture is responsible for a significant por-tion of nitrogen emissions. Livestock production, concentrated in some European re-gions, is the major contributor for ammonia emission, accounting almost 60% of the total, with losses of reactive nitrogen that occur along the whole manure management chain, from animal houses to storages of slurry and finally the spreading on agricul-tural land. With the increasing concern about the impacts of livestock production on natural resources and public health, international regulations have gone into effect with the objective of mitigating nitrogen emissions (N2O and NH3) to the atmosphere. Italy, in particular the North of the Country, presents a great development of animal husbandry and most of the agricultural land in Po Valley is considered a Nitrate Vul-nerable Zone (NVZ) according to Nitrates Directive 91/676/EEC. However most of the studies on ammonia and nitrous oxide emission from slurry and related mitigation strategies come from north countries of Europe. For this reason, it is a priority to ad-just emission assessments to the particular Mediterranean conditions, and finding mit-igation strategies to limit nitrogen losses in these environments. Therefore, the current Ph.D. thesis was proposed with the aim of giving a contribute in the field of research on nitrogen assessment, with a special regard to emissions of ammonia from slurry management in innovative agricultural systems, such as Short Rotation Coppice Crops. Given the complexity of the issue this thesis has been organized in chapters, 6 that aim at presenting every aspect analyzed during three years of PhD and give an homogeneous framework of this work. In general, the following chapters have these outcomes (general conclusions): Chapter 1: it synthetizes the state of the art on nitrogen losses from slurry chain, that is basically the sum of ammonia emission from storages and nitrogen losses (via leach-ing, emission and denitrification) from the application of slurry on agricultural land. Mitigation strategies (covers, short rotation coppice crops, distribution techniques) are presented, and measurement theories and techniques are introduced. Chapter 2: a new model to simulate ammonia emission from slurry storages is intro-duced. The emission from slurry storages can vary largely depending on climate re-gime and management techniques, that include the type of storage and the adoption of mitigation strategies. Chapter 3: a nitrogen balance, collecting data from field experiments on leaching, emission and nitrogen content of biomass has been done. Forested infiltration areas, where short rotation crops have been established, showed a good performance in the mature stage, whereas in the initial stage of the plantation the advantages were not relevant in comparison with traditional agricultural systems (Permanent meadow, Maize) Chapter 4: a new model that simulates the growth of poplar and willow plantation has been developed. The yield of biomass crops can vary largely depending on soil charac-teristics and climate. The main results of this work consists in the vast ensemble of en-vironmental and biological processes that this model can simulate. The relationship that links ageing of a plantation to biomass yield could be considered theoretical ad- 7 vancement for this category of crop models. To limit the problems that come from ex-cess of reactive nitrogen in the environment, a set of solutions has been proposed in this thesis. These measures should be implemented all together accompanied with pre-cise estimations of the ammonia emissions, on which still there is a great uncertainty.