Sources of N2O in organic grass-clover pastures.

Organic farming practises, and in particular dairy production systems based on grass-clover pastures are becoming increasingly abundant within Danish agriculture. Grass-clover pastures may provide a mitigation option to reduce grassland nitrous oxide (N2O) emissions (Velthof et al. 1998). The objectives of this work was to examine the relationship between N2O emissions and transformations of inorganic N in organically managed grass-clover pastures of different ages. Results from the project will be used for calibration of the FASSET whole-farm nitrogen transformation model

Conservation agriculture and climate change

This chapter review aims at developing a clear understanding of the impacts and benefits of conservation agriculture (CA) with respect to climate change, and examining if there are any misleading findings at present in the scientific literature. Most of the world’s agricultural soils have been depleted of organic matter and soil health over the years under tillage-based agriculture (TA), compared with their state under natural vegetation. This degradation process can be reversed and this chapter identifies the conditions that can lead to increase in soil organic matter content and improvement in soil health under CA practices which involve minimum soil disturbance, maintenance of soil cover, and crop diversity. The chapter also discusses the need to refer to specific carbon pools when addressing carbon sequestration, as each carbon category has a different turnover rate. With respect to greenhouse gas emissions, sustainable agricultural systems based on CA principles are described which result in lower emissions from farm operations as well as from machinery manufacturing processes, and that also help to reduce fertilizer use. This chapter describes that terrestrial carbon sequestration efficiently be achieved by changing the management of agricultural lands from high soil disturbance, as TA practices to low disturbance, as CA practices, and by adopting effective nitrogen management practices to provide a positive nitrogen balance for carbon sequestration. However, full advantages of CA in terms of carbon sequestration can usually be observed only in the medium to longer term when CA practices and associated carbon sequestration processes in the soil are well established