APEX MODEL APPLICATIONS FOR THE MEDITERRANEAN CROPPING SYSTEMS SIMULATION Roberto Orsini 1 , Evelyn Steglich 2 , Luca Doro 3 , Paolo Trobbiani 1 , Marco Toderi 1 , Martina Perugini 1 , Giacomo De Sanctis 4-5 , Giovanna Seddaiu 3 , Jimmy R. Williams 2 , Pier Paolo Roggero 3* 1 Dip. di Scienze Agrarie, Alimentari ed Ambientali, Università Politecnica delle Marche, Ancona, Italy 2 Texas AgriLife Research, Blackland Research and Extension Center, Temple, Texas 3 Dip. di Agraria, Università degli Studi di Sassari, Italy 4 MIPAAF, Dip. politiche competitive del mondo rurale e della qualità, via XX Settembre, Roma, Italy 5 INRA, AgroClim, Domaine Saint-Paul, Site Agroparc, Avignon, France. * pproggero@uniss.it Abstract The Agricultural Policy/Environmental eXtender model (APEX) extends the EPIC (Environmental Policy Integrated Climate model) capabilities for applications at the microcatchment scale. The research described aims to calibrate APEX to simulate industrial-cereal cropping systems in order to identify management strategies capable of reducing the environmental impact in relation to hypothetical scenarios of climate change and to develop mitigation strategies that allow for direct agricultural activities towards sustainable production. Good correlations between observed and simulated values were obtained for crop productivity as shown by the low Root Mean Square Error (RMSE) obtained. APEX provided valuable results on the runoff quantification, in particular for the higher levels. In the analyzed context APEX can be a useful tool for environmental planning and implementation of sustainable cropping systems. Keywords APEX, runoff, microcatchment, hilly landscape Introduction The Agricultural Policy/Environmental eXtender model (APEX) has been developed for applications at the microcatchment scale (Williams and Izaurralde, 2006). APEX extends the capabilities of EPIC (Environmental Policy Integrated Climate model) (Williams et al., 1984, 1989; Williams, 1995) offering the possibility of dividing the microcatchment into homogeneous subareas from the standpoint of the climate and soil characteristics to simulate surface and subsurface water flow and the transport of nutrients, sediment and pesticides from the different subareas to the catchment outlet. The APEX model was used at the regional scale in Texas to assess the influence of organic fertilizer management on water quality (Flowers et al., 1996) and at the national scale for planning of water erosion control vegetation zones (Arnold et al., 1998). The research described aims to evaluate the ability of APEX to simulate central Italian industrial-cereal systems in order to identify management strategies capable of reducing the environmental impact in relation to hypothetical scenarios of climate change. Materials and Methods APEX has been applied on a microcatchment of the coastal hills of Marche region (Central Italy) located in Serra dè' Conti (AN), named Spescia (80 ha of total agricultural surface, 70 ha of arable land, 43° 33' N, 13° 04 'E ). Spescia has been continually monitored since 1998 for the following variables partly used as model input: - agricultural practices (sowing date, timing and rate of fertilizer applications, depth and type of tillage, weed control applications, harvest date); - crop yield and N and P contents of the yield; - surface and subsurface water quality; - weather parameters characterization (ASSAM Regional agrometeorological service); - physical, chemical and hydrological soil characteristics (Corti et al., 2006). In the decade 1998-2007 the cropping system common in the microcatchment was based on rotation of durum wheat or grain legumes (pea and faba bean) with spring-summer cycle crops (sunflower, sugar beet and maize) (Orsini et al., 2008). For the application of APEX Spescia was divided into homogeneous subareas based on hydrological, soil and cultivation technique characteristics. To this end 15 subareas have been identified. They are characterized by a single outlet interconnected, compatible with the existing drainage network, with the outlets hierarchically lower. The degree days accumulated by the crops in the individual sub- areas together with biometric information obtained from experiments conducted in similar contexts have been considered for the crop calibrations. Results and Discussion During the field monitoring period an average of 857 mm (err. st. = ± 57 mm) of precipitation was observed. The thermal trend was characteristic of the Mediterranean environment with cold winters (minimum average temperature: 3.4 °C) and hot summers (average maximum temperature: 24.7 °C). APEX simulated the production of main crops in rotation well (Fig. 1). With regard to runoff, an overestimation was detected particularly when heavy summer rainfall occurred. In fact, the soil fractures present at that time of the season ensure rapid water infiltration thus reducing the runoff (Fig. 2).