N. Ferreiro-Domínguez

Sewage sludge fertiliser use: Implications for soil and plant copper evolution in forest and agronomic soils

Fertilisation with sewage sludge may lead to crop toxicity and environmental degradation. This study aims to evaluate the effects of two types of soils (forest and agronomic), two types of vegetation (unsown (coming from soil seed bank) and sown), and two types of fertilisation (sludge fertilisation and mineral fertilisation, with a no fertiliser control) in afforested and treeless swards and in sown and unsown forestlands on the total and available Cu concentration in soil, the leaching of this element and the Cu levels in plant. The experimental design was completely randomised with nine treatments and three replicates. Fertilisation with sewage sludge increased the concentration of Cu in soil and plant, but the soil values never exceeded the maximum set by Spanish regulations. Sewage sludge inputs increased both the total and Mehlich 3 Cu concentrations in agronomic soils and the Cu levels in plant developed in agronomic and forest soils, with this effect pronounced in the unsown swards of forest soils. Therefore, the use of high quality sewage sludge as fertiliser may improve the global productivity of forest, agronomic and silvopastoral systems without creating environmental hazards.

Farmers’ reasoning behind the uptake of agroforestry practices: evidence from multiple case-studies across Europe

Potential benefits and costs of agroforestry practices have been analysed by experts, but few studies have captured farmers’ perspectives on why agroforestry might be adopted on a European scale. This study provides answers to this question, through an analysis of 183 farmer interviews in 14 case study systems in eight European countries. The study systems included high natural and cultural value agroforestry systems, silvoarable systems, high value tree systems, and silvopasture systems, as well as systems where no agroforestry practices were occurring. A mixed method approach combining quantitative and qualitative approaches was taken throughout the interviews. Narrative thematic data analysis was performed. Data collection proceeded until no new themes emerged. Within a given case study, i.e. the different systems in different European regions, this sampling was performed both for farmers who practice agroforestry and farmers who did not. Results point to a great diversity of agroforestry practices, although many of the farmers are not aware of the term or concept of agroforestry, despite implementing the practice in their own farms. While only a few farmers mentioned eligibility for direct payments in the CAP as the main reason to remove trees from their land, to avoid the reduction of the funded area, the tradition in the family or the region, learning from others, and increasing the diversification of products play the most important role in adopting or not agroforestry systems.

Spatial similarities between European agroforestry systems and ecosystem services at the landscape scale

Agroforestry systems are known to provide ecosystem services which differ in quantity and quality from conventional agricultural practices and could enhance rural landscapes. In this study we compared ecosystem services provision of agroforestry and non-agroforestry landscapes in case study regions from three European biogeographical regions: Mediterranean (montado and dehesa), Continental (orchards and wooded pasture) and Atlantic agroforestry systems (chestnut soutos and hedgerows systems). Seven ecosystem service indicators (two provisioning and five regulating services) were mapped, modelled and assessed. Clear variations in amount and provision of ecosystem services were found between different types of agroforestry systems. Nonetheless regulating ecosystems services were improved in all agroforestry landscapes, with reduced nitrate losses, higher carbon sequestration, reduced soil losses, higher functional biodiversity focussed on pollination and greater habitat diversity reflected in a high proportion of semi-natural habitats. The results for provisioning services were inconsistent. While the annual biomass yield and the groundwater recharge rate tended to be higher in agricultural landscapes without agroforestry systems, the total biomass stock was reduced. These broad relationships were observed within and across the case study regions regardless of the agroforestry type or biogeographical region. Overall our study underlines the positive influence of agroforestry systems on the supply of regulating services and their role to enhance landscape structure.

Sewage sludge stabilisation and fertiliser value in a silvopastoral system developed with Eucalyptus nitens Maiden in Lugo (Spain)

Copper (Cu) is one of the heavy metals with highest proportion in sewage sludge. In Europe, sewage sludge should be stabilised before using it as a fertiliser in agriculture. Depending on the stabilisation process, sewage sludge has different Cu contents, and soil Cu incorporation rates. This study was undertaken to examine the effect of fertilisation with different types of sewage sludge (anaerobic, composted, and pelletised) on the concentration of total and available Cu in the soil, the tree growth, the pasture production, and the concentration of Cu in the pasture when compared with control treatments (i.e. no fertilisation and mineral fertilisation) in a silvopastoral system under Eucalyptus nitens Maiden. The results of this experiment show that an improvement of the soil pH increased the incorporation and the mineralisation of the sewage sludge and litter, and therefore, the release of Cu from the soil. Moreover, the concentration of Cu in the pasture and the levels of Cu extracted by the pasture improved when the soil organic matter decreased because the high levels of organic matter in the soil could have formed Cu complex. The composted sewage sludge (COM) increased a) the soil variables studied (pH, total Cu, and available Cu) and b) the Cu extracted by the pasture, both probably due to the higher inputs of cations made with it. In any case, the levels of Cu found in the soil never exceeded the maximums as set by Spanish regulations and did not cause harmful effects on the plants and animals. Therefore, the use of COM as an organic fertiliser should be promoted in silvopastoral systems established in edaphoclimatic conditions similar to this study because COM enhanced the productivity of the system from a viewpoint of the soil and the pasture, without causing any environmental damage.

Agroforestry in the European common agricultural policy

Agroforestry is a sustainable land management system that should be more strongly promoted in Europe to ensure adequate ecosystem service provision in the old continent (Decision 529/2013) through the common agricultural policy (CAP). The promotion of the woody component in Europe can be appreciated in different sections of the CAP linked to Pillar I (direct payments and Greening) and Pillar II (rural development programs). However, agroforestry is not recognised as such in the CAP, with the exception of the Measure 8.2 of Pillar II. The lack of recognition of agroforestry practices within the different sections of the CAP reduces the impact of CAP activities by overlooking the optimum combinations that would maximise the productivity of land where agroforestry could be promoted, considering both the spatial and temporal scales.

Integrating belowground carbon dynamics into Yield-SAFE, a parameter sparse agroforestry model

Agroforestry combines perennial woody elements (e.g. trees) with an agricultural understory (e.g. wheat, pasture) which can also potentially be used by a livestock component. In recent decades, modern agroforestry systems have been proposed at European level as land use alternatives for conventional agricultural systems. The potential range of benefits that modern agroforestry systems can provide includes farm product diversification (food and timber), soil and biodiversity conservation and carbon sequestration, both in woody biomass and the soil. Whilst typically these include benefits such as food and timber provision, potentially, there are benefits in the form of carbon sequestration, both in woody biomass and in the soil. Quantifying the effect of agroforestry systems on soil carbon is important because it is one means by which atmospheric carbon can be sequestered in order to reduce global warming. However, experimental systems that can combine the different alternative features of agroforestry systems are difficult to implement and long-term. For this reason, models are needed to explore these alternatives, in order to determine what benefits different combinations of trees and understory might provide in agroforestry systems. This paper describes the integration of the widely used soil carbon model RothC, a model simulating soil organic carbon turnover, into Yield-SAFE, a parameter sparse model to estimate aboveground biomass in agroforestry systems. The improvement of the Yield-SAFE model focused on the estimation of input plant material into soil (i.e. leaf fall and root mortality) while maintaining the original aspiration for a simple conceptualization of agroforestry modeling, but allowing to feed inputs to a soil carbon module based on RothC. Validation simulations show that the combined model gives predictions consistent with observed data for both SOC dynamics and tree leaf fall. Two case study systems are examined: a cork oak system in South Portugal and a poplar system in the UK, in current and future climate.

Global and European policies to foster agricultural sustainability: agroforestry

Agroforestry is a sustainable land management system recognized worldwide but not implemented in a extensive form in temperate and developed countries. Agroforestry has been promoted in the last decades at global level as it provides more efficient and sustainable farming systems. This review aims at summarizing the main research findings explaining why agroforestry is a sustainable land management that fulfils and is affected by different Global, Pan-European and European policies as well as how innovation is currently fostered in Europe, therefore linking research, policy and innovation. This review specially targets researchers and policy makers working in integrated land systems. There is a global and European recognition of the role that agroforestry can play to provide products but also to deliver highly important ecosystem services. However, the promotion of agroforestry practices at European level is still not well addressed by the Common Agricultural Policy. The clear identification of agroforestry practices, the link of management plans to establish agroforestry pursuing a final eligible tree density for the Pillar I payments should be addressed as initial steps to foster agroforestry in Europe. There is a lack of knowledge transfer that promotes agroforestry at field level, which should be approached by using stakeholder integration within the policy development as it is currently done by the EIP-Agri.