Effect of Good Agricultural and Environmental Conditions on erosion and soil organic carbon balance: A national case study

Pasquale Borrelli,Keith Paustian,Panos Panagos,Arwyn Jones,Brigitta Schütt,Emanuele Lugato

doi:10.1016/j.landusepol.2015.09.033

Abstract

Since, the Common Agricultural Policies (CAP) reform in 2003, many efforts have been made at the European level to promote a more environmentally friendly agriculture. In order to oblige farmers to manage their land sustainably, the GAEC (Good Agricultural and Environmental Conditions) were introduced as part of the Cross Compliance mechanism. Among the standards indicated, the protection of soils against erosion and the maintenance of soil organic matter and soil structure were two pillars to protect and enhance the soil quality and functions. While Member States should specifically define the most appropriate management practices and verify their application, there is a substantial lack of knowledge about the effects of this policy on erosion prevention and soil organic carbon (SOC) change. In order to fill this gap, we coupled a high resolution erosion model based on Revised Universal Soil Loss Equation (RUSLE) with the CENTURY biogeochemical model, with the aim to incorporate the lateral carbon fluxes occurring with the sediment transportation. Three scenarios were simulated on the whole extent of arable land in Italy: (i) a baseline without the GAEC implementation; (ii) a current scenario considering a set of management related to GAEC and the corresponding area of application derived from land use and agricultural management statistics and (iii) a technical potential where GAEC standards are applied to the entire surface. The results show a 10.8% decrease, from 8.33Mgha−1 year−1 to 7.43Mgha−1 year−1, in soil loss potential due to the adoption of the GAEC conservation practices. The technical potential scenario shows a 50.1% decrease in the soil loss potential (soil loss 4.1Mgha−1 year−1). The GAEC application resulted in overall SOC gains, with different rates depending on the hectares covered and the agroecosystem conditions. About 17% of the SOC change was attributable to avoided SOC transport by sediment erosion in the current scenario, while a potential gain up to 23.3Mt of C by 2020 is predicted under the full GAEC application. These estimates provide a useful starting point to help the decision-makers in both ex-ante and ex-post policy evaluation while, scientifically, the way forward relies on linking biogeochemical and geomorphological processes occurring at landscape level and scaling those up to continental and global scales.

Highlights

Land degradation due to soil erosion is an old threat (Chapline, 1929; Ayres, 1936) which has turned into a major agricultural and environmental problem worldwide (Lal, 2014)
The high soil erosion rates reflect the heterogeneity and propensity of the landscape to erosion, where locally the annual average rainfall erosivity can be as high as 6200 MJ mm ha−1 h−1 year−1 ( = 1558 MJ mm ha−1 h−1 year−1) and the slopes on cultivated land can exceed the 15% (13.9% of the study area)
Moderate and high erosion values are simulated for 15.4% and 16.5% of the study area, respectively. These soil loss classes typically occur in hilly areas of transition towards the Apennine regions and where the rain hits the ground with high energy (e.g., Friuli Venezia Giulia (ITH4), such as in Liguria (ITC3) and Campania (ITF3))

Summary

Introduction

Land degradation due to soil erosion is an old threat (Chapline, 1929; Ayres, 1936) which has turned into a major agricultural and environmental problem worldwide (Lal, 2014). P. Borrelli et al / Land Use Policy 50 (2016) 408–421. 2015; Oldroyd, 2015), soil erosion and land degradation remain significant threats for most agricultural lands (Bai et al, 2008) and constitute a limiting factor for the per capita food production growth in several locations especially in the African countries (Nachtergaele et al, 2010; FAO, 2015). Erosion rates accelerated by unsuitable land-use and management (Felix-Henningsen et al, 1997) affect soil fertility and productivity by reducing the water infiltration, water-holding capacity, organic matter, nutrients and organic biota (Morgan, 2009). The soil is still moved by erosion carrying nutrients, pesticides, and other harmful farm chemicals into the receiving stream (Hodgkin and Hamilton, 1993; Novotny, 1999)

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