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

• Published in: Agronomy for sustainable development 2010-04, Vol.30 (2), p.215-236
• Main Authors: Novak, S. M., Fiorelli, J. L.
• Format: Article
• Language: English
• 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
• 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 quickl