Fruit tree orchards have a historical and economic importance for Mediterranean agriculture, notably in Spain. Fruit tree orchards have the potential to mitigate global warming by sequestrating carbon (C) and providing renewable fuels. Actually, there is few information on the benefits of organic practices. Therefore, we analyzed the greenhouse gas contribution of 42 pairs of organic and conventional perennial cropping systems, including citrus, subtropical trees, other fruit trees, treenuts, vineyards, and olives, using life-cycle assessment (LCA). The assessment was based on management information from interviews and involved the estimation of soil carbon sequestration, specific Mediterranean N 2 O emission factors, and the consideration of coproducts. Results show on average a 56 % decrease of greenhouse gas emissions under organic versus conventional cropping, on an area basis. On a product basis, greenhouse gas emissions decreased by 39 % on average. These findings are explained mainly by C sequestration in soils, which is due in turn to higher C inputs by cover cropping and incorporation of pruning residues.

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The use of non-renewable energy in farming, a factor which considerably reduces its energy efficiency, continues to increase. Moreover, there is growing worldwide concern regarding the emission of greenhouse gases and their effect on our climate, which is directly related to the use of fossil energy. All this creates a need for energy studies on changing tendencies in the management of agricultural systems, among which we find that of organic farming. This article uses energy balances to evaluate the contribution of organic farming to the increase of energy efficiency in Spanish agriculture. To achieve this objective, comparative studies were carried out on 78 organic crops and their conventional counterparts. Primary data were obtained via direct surveys carried out at farms distributed across the whole of Spain. The results indicate that non-renewable energy efficiency is higher in organic farming, whilst the consumption of this type of energy is lower. For this reason, although certain qualifications are made regarding the factors which can influence these results, an increase in the land area dedicated to organic farming would considerably improve the energy sustainability of Spanish agriculture.

Agriculture is a major driver of climate change, particularly when all indirect emission sources are accounted for. Mitigation options targeted on one process are often proposed, ignoring their secondary effects on the overall greenhouse gas balance. Integrative methodologies such as life cycle assessment (LCA) are often applied without adjusting emission factors to specific site characteristics. Here, we used LCA to calculate the global warming potential of 38 pairs of organic and conventional herbaceous cropping systems and products in Spain. Crop products included rainfed cereals and pulses, rice, open-air vegetables, and greenhouse vegetables. We used data from farmer interviews and published conversion factors. Our results show that the emission balances were dominated by fossil fuel use rather than by direct field emissions. Organic management reduced crop emissions by 36-65 %, with the exception of rice showing an increase of 8 % due to methane generation. Productbased emissions of organic crops were also lower by 30 % on average, except for rice.