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1. Study site description

1.1 Geographical location

The Cértima River, located in north-central Portugal, is a sub-tributary of the Vouga River, a watercourse that drains into the Atlantic Ocean via the Ria de Aveiro coastal lagoon. The Cértima River has a total length of 43 km, from its headwaters on the west flank of the Buçaco mountain range to its outlet at Requeixo. It drains an area of about 540 km² that ranges from 4 to 563 m in elevation. In its lower section, the river valley opens broadly to form one of the largest natural freshwater lakes of the Iberian Peninsula (approximately 5.3 km²) - the Pateira de Fermentelos Lake - which is considered a sensitive wetland and is classified as a RAMSAR site.

1.2 Main farming systems and typical agricultural management activities in the study area

The land cover in the Cértima River Basin consists of a mixture of agricultural lands (44%), forest plantations (48%) and built-up areas (7%) (CLC, 2006; INE-EA, 2011). While forest plantations are dominated by pure and mixed stands of Pinus pinaster and Eucalyptus globulus, the agricultural lands are predominantly permanent crop lands and, in particular, vineyards (27%). The arable lands make up a heterogeneous and complex pattern of annual croplands where mainly potato, corn, oat are cultivated, together with annual and permanent pastures. Animal rearing in the Cértima River Basin is dominated by chicken farms (95%), rabbit (2.2%), pig (1.5%), and cow (0.5%) farms.

Land use practices continue to be highly traditional, involving frequent soil mobilization, limited crop rotation, and excessive use of fertilizers and phyto-pharmaceuticals (INE-EA, 2011). In recent years, however, several of the wine producers that pertain to the Bairrada winegrowing region are increasingly adopting protective and integrated agricultural practices; first and foremost to improve and promote the quality of their products. These integrated agricultural practices comprise, in essence, a substantial reduction in the frequency of soil mobilization operations, including reduced soil erosion risk, sustainable use of fertilizers for ensuring normal plant development, and minimized application of pesticides and herbicides for promoting biodiversity and limiting pollution of soils in downstream aquatic and flood zone habitats (DGPC, 2005).

1.3 Characteristic soils and soil quality monitoring practice

The soils in the Cértima River Basin are dominated by Humic Cambisols in its eastern, upland areas and by Podzols in western parts (Cardoso et al., 1971, using the FAO-2006 classification). These Humic Cambisols are developed from Ordovician schists, whereas the Podzols are formed on modern-age alluvial sands and clays. There is no regular monitoring program for soil quality in place in the Cértima River Basin, in spite of the Portuguese Environmental Agency being officially responsible for evaluating soil fertility and contamination.

1.4  Previous research and innovation actions on soil improvement and monitoring

Following earlier work focusing on surface water quality and the WFD (Cerquieira et al., 2005; Ferreira et al., 2009; Serpa et al., 2014), the nationally-funded VITAQUA project has been studying soil contamination by agri-chemicals including soil erosion and associated transport of agri-chemicals in the vineyards of the Cértima River Basin. To this end, the “São Lourenço” experimental research basin was instrumented with a hydrometric station (including automatic sampler), various rainfall gauges and various runoff plots, and is being monitored on a 1 to 2-weekly basis since 2011.

More recently, an innovative field experiment with biochar was started in a vineyeard within the research station of the Vitivinicola da Bairrada (EVB), Anadia. The motivation for this experiment was two-fold, i.e. i) vineyards of the Bairrada region are increasingly experiencing water stress in the dry growing season, and ii), biochar has been found to improve soil infiltration and water holding capacity, thereby not only increasing plant-available water but also reducing soil erosion risk. The experiment’s objectives are therefore to assess the effects of biochar on soil hydrology, soil quality and crop production. Since March 2013, data is being recorded on soil moisture content, soil water potential, soil temperature, and soil electric conductivity. In addition, crop physiological variables such as chlorophyll fluorescence, stomatal conductance, leaf pigment content and hydric stress have been monitored on three occasions. Also, grape yield and aboveground vine biomass data, have been collected by personnel of the EVB (testimony of the interest of both the EVB and the DRAP-C). Finally, a time series of soil samples is being analysed for eco-toxicological effects of applied biochar, in terms avoidance/survival of earthworms, isopods, and springtails.

2. Participation of stakeholders in the iSQAPER research programme

The local stakeholders listed in Table 1 were involved throughout the duration of iSQAPER in a number of research tasks including: providing experimental sites for the soil quality assessment and agricultural management practice evaluation; testing and evaluating SQAPP; attending demonstration workshops.

Table 1: Local stakeholders involved in the iSQAPER research programme

3. Research tasks

Soil quality assessment and agricultural management practice evaluation

Based on WOCAT database (www.wocat.net), iSQAPER selected 18 promising agricultural management practices (AMPs) with potential to improve soil quality (»Agricultural management practices in the iSQAPER study sites). Thirteen examples of a number of these AMPs were identified in the Cértima study site that conformed to the following criteria:

1. the promising management practice has been implemented for at least 5 years;
2. at least 2 different soil types are represented; and
3. at least in 2 different first level Farming Systems (arable, permanent, grazing) are represented.

For each AMP plot, nearby control plots were also identified where the practice has not changed.

Table 2: AMPs identified in the Cértima study site. Climatic region: Mediterranean temperate

*Note: see »Assessing effect of management practices on soil quality - experimental framework for the full list and descriptions of the 18 promising agricultural management practices.

A first field campaign was conducted in 2016 to evaluate the soil quality in each of the paired AMP-control plots, using visual soil assessment methods (»Visual soil and plant quality assesment) plus chemical and physical assessments. The results from this and all the other study sites were combined to determine which AMPs can be shown to have a proven positive effect on soil quality, see »Assessing effect of management practices on soil quality - experimental results.

Those practices that are innovative for Portugal were also described and added to the WOCAT database

• »Minimum tillage in Mediterranean vineyards [Portugal]

The soil assessment campaign was repeated in 2018 on the two paired plots highlighted in green in Table 2 (3.2: Sludge from domestic wastewater treatment plant / Mulching and 3.7: Water diversion and drainage) with laboratory-based measurements added to the visual soil assessments. The aim was to investigate

• how measurements of soil quality parameters obtained from the visual assessments compared to those obtained from laboratory measurements;
• if different AMPs affected different soil quality parameters in different ways;
• and what impact the AMPs had on the principal soil threats.

For details of the assessment analysis methods and the results from this and all study sites see »Impact of promising agricultural management practices.

As a result of this extended analysis, the example of residue maintenance/ mulching that was exemplified in Plot 3.2 (in which sewage sludge is applied to maize) was finally selected to demonstrate the positive impact management practice can have on soil quality (see »Demonstration events in the study sites).

Soil properties
Soil threats

This practice addresses soil organic matter decline. Laboratory analysis shows that when sewage sludge is applied to the soil, organic carbon almost doubles, NPK levels are higher and bulk density is much lower. However, higher levels of copper have also been observed which may be a residue from previous land use.

SQAPP development, testing and evaluation

Of the 90 stakeholders who took part in the evaluation of the beta version of SQAPP, 12 were from the Cértima study site. Participants were asked a series of questions relating to their expectations of SQAPP and the relevance of the soil parameters included in SQAPP, the assessment of soil threats and the suitability of the app's recommendations to their local context. The feedback and comments were combined with those from the other study sites and used in the further development of SQAPP. For details of the responses from all study sites see »Stakeholder feedback and SQAPP development.

Demonstration workshop

On 29 October 2019 a demonstration event was organised in the Cértima study site to present the major findings of iSQAPER to stakeholders and to demonstrate the application and incorporation of sewage sludge as a management practice of proven benefit to soil quality. The event was attended by 32 participants.

The results from this demonstration event and those held in the other study sites are summarised in »Demonstration events in the study sites.

A leaflet describing the AMP sewage sludge incorporation was prepared to accompany the demonstrations.

 »Sewage sludge incorportation, Portugal

4. Long-term impact of iSQAPER's research programme in the study site

Taking account discussions with the stakeholders and feedback from the various research tasks and events in which they took part, it is anticipated that the iSQAPER research programme could have a lasting legacy in the Cértima study site as indicated in Table 3.

Table 3: Activities in which iSQAPER's research programme could potentially have a lasting impact in the Cértima study site