Greenhouse gases and ammonia emissions from organic mixed crop-dairy systems: a critical review of mitigation options

• Published in: Agronomy for sustainable development Vol. 30; no. 2; pp. 215 - 236
• Main Authors: Novak, S. M., Fiorelli, J. L.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.04.2010; EDP Sciences; Springer Verlag/EDP Sciences/INRA
• Subjects: Agricultural sciences; Agriculture; Agronomy. Soil science and plant productions; Animal productions; Biological and medical sciences; Biomedical and Life Sciences; Cropping systems. Cultivation. Soil tillage; Ecology, environment; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Generalities. Cropping systems and patterns; Life Sciences; Review Article; Soil Science & Conservation; Sustainable Development; Terrestrial animal productions; Vertebrates; Europe; agriculture; carbon storage; manure; livestock; ammonia; mixed crop-dairy systems; soil carbon sequestration; abatement; organic; grassland; greenhouse gas; Grassland; Organic waste; Gas emission; Nitrogen compounds; Immobilization; Review; Inorganic element; Agronomy; Greenhouse gas; Agriculture; Animal production; Non metal; Macronutrient(mineral); Farming animal; Cropping system; Group IVA element; Carbon; Carbon sequestration; Milk production; Ammonia; Soils; Mixed cropping; Inorganic nitrogen; Mitigation measure; Critical study; Livestock
• ISSN: 1774-0746; 1773-0155
• DOI: 10.1051/agro/2009031

Dairy production systems represent a significant source of air pollutants such as greenhouse gases (GHG), that increase global warming, and ammonia (NH 3 ), that leads to eutrophication and acidification of natural ecosystems. Greenhouse gases and ammonia are emitted both by conventional and organic dairy systems. Several studies have already been conducted to design practices that reduce greenhouse gas and ammonia emissions from dairy systems. However, those studies did not consider options specifically applied to organic farming, as well as the multiple trade-offs occurring between these air pollutants. This article reviews agricultural practices that mitigate greenhouse gas and ammonia emissions. Those practices can be applied to the most common organic dairy systems in northern Europe such as organic mixed crop-dairy systems. The following major points of mitigation options for animal production, crop production and grasslands are discussed. Animal production: the most promising options for reducing greenhouse gas emissions at the livestock management level involve either the improvement of animal production through dietary changes and genetic improvement or the reduction of the replacement rate. The control of the protein intake of animals is an effective means to reduce gaseous emissions of nitrogen, but it is difficult to implement in organic dairy farming systems. Considering the manure handling chain, mitigation options involve housing, storage and application. For housing, an increase in the amounts of straw used for bedding reduces NH 3 emissions, while the limitation of CH 4 emissions from deep litter is achieved by avoiding anaerobic conditions. During the storage of solid manure, composting could be an efficient mitigation option, depending on its management. Addition of straw to solid manure was shown to reduce CH 4 and N 2 O emissions from the manure heaps. During the storage of liquid manure, emptying the slurry store before late spring is an efficient mitigation option to limit both CH 4 and NH 3 emissions. Addition of a wooden cover also reduces these emissions more efficiently than a natural surface crust alone, but may increase N 2 O emissions. Anaerobic digestion is the most promising way to reduce the overall greenhouse gas emissions from storage and land spreading, without increasing NH 3 emissions. At the application stage, NH 3 emissions may be reduced by spreading manure during the coolest part of the day, incorporating it quickly and in narrow bands. Crop production: the mitigation options for crop production focus on limiting CO 2 and N 2 O emissions. The introduction of perennial crops or temporary leys of longer duration are promising options to limit CO 2 emissions by storing carbon in plants or soils. Reduced tillage or no tillage as well as the incorporation of crop residues also favour carbon sequestration in soils, but these practices may enhance N 2 O emissions. Besides, the improvement of crop N-use efficiency through effective management of manure and slurry, by growing catch crops or by delaying the ploughing of leys, is of prime importance to reduce N 2 O emissions. Grassland: concerning grassland and grazing management, permanent conversion from arable to grassland provides high soil carbon sequestration while increasing or decreasing the livestock density seems not to be an appropriate mitigation option. From the study of the multiple interrelations between gases and between farm compartments, the following mitigation options are advised for organic mixed crop-dairy systems: (1) actions for increasing energy efficiency or fuel savings because they are beneficial in any case, (2) techniques improving efficiency of N management at field and farm levels because they affect not only N 2 O and NH 3 emissions, but also nitrate leaching, and (3) biogas production through anaerobic digestion of manure because it is a promising efficient method to mitigate greenhouse gas emissions, even if the profitability of this expensive investment needs to be carefully studied. Finally, the way the farmer implements the mitigation options, i.e. his practices, will be a determining factor in the reduction of greenhouse gas and NH 3 emissions.