Suchergebnisse

In semiarid agroecosystems of the Ebro valley (NE Spain) soils are characterized by low soil organic matter (SOM) and a weak structure. In this study we investigated the individual and combined effect of tillage system (no-tillage, NT; reduced tillage, RT; conventional tillage, CT) and cropping system (barley–fallow rotation at the Peñaflor site, PN-BF and continuous barley at the Peñaflor site, PN-BB) on soil organic carbon (SOC) storage as well as the physical protection of SOM fractions by soil aggregates in three long-term experimental sites. In both cropping systems, total SOC content was more than 30% higher in NT compared with CT in the 0- to 5-cm depth. The suppression of fallowing in the PN-BB cropping system led to a greater SOC stabilization only in NT. In all the three sites, greater proportion of water-stable macroaggregates (>250 µm) was found under NT than under CT in the 0- to 5-cm depth. Macroaggregate organic C concentration (250–2000 µm) was greater in NT compared with CT in the BB cropping system, but did not differ with tillage treatment in the PN-BF rotation. Greater proportion of microaggregates within macroaggregates in NT compared with CT was only found in the Agramunt site (AG). However, greater C stabilized inside these microaggregates was observed in AG, Selvanera site (SV), and PN-BB in the 0- to 5-cm depth. The results of this study demonstrate that in the semiarid Mediterranean agroecosystems of the Ebro valley, the adoption of NT together with the suppression of long-fallowing period can significantly increase the amount of SOC stabilized in the soil surface and improve soil structure and aggregation. ; This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (Grants AGL2001-2238-CO2-01, AGL 2004-07763-C02-02 and AGL2007-66320-CO2-02/AGR) and the European Union (FEDER funds). ; Peer reviewed

The GHG (greenhouse gas) mitigation potential from the agricultural sector is set to increase in coming decades. Much of the agricultural mitigation potential lies in developing countries where systems are dominated by smallholder farmers. There is therefore an opportunity for smallholders not only to gain environmental benefits from carbon friendly practices, but also to receive much needed financial input, either directly from carbon financing, or from development agencies looking to support carbon friendly activities. However, the problem remains of how to quantify carbon gains from mitigation activities carried out by smallholder farmers. Landscape-scale quantification enables farmers to pool resources and expertise, which can put participation in carbon markets and access to other funding sources, within their reach. Therefore, funding agencies, governments and NGOs are increasingly recognizing the benefits of taking a landscape approach to GHG quantification. This paper gives an overview of approaches that have been taken to date for landscape-scale GHG quantification, covering both measurement and modelling and the reliance of one upon the other. The discussion covers ground-based measurement approaches for carbon stock changes in biomass and soils, methods for measuring GHG flux and the application of remote sensing techniques. Computational approaches for estimating carbon stock changes and GHG emissions are discussed, in addition to the use of more complex dynamic ecosystem models. This is followed by an analysis of some of the resources that are available for those wishing to do GHG quantification at the landscape scale in areas dominated by smallholders. This analysis is intended to provide an aid to funding agencies, government agencies, NGOs, academics and others. Information for this section comes from questionnaires distributed to selected resource developers.