Caldeirão, Portugal

Study Site Trials

The SICS selected for trialling in this Study Site are described below:

General Treatment Category	Study Site Trials
Soil-imrpving crops, Crop rotations,	1. Bico da Barca - Organic rice in rotation with perennial lucerne - Conventional rice monoculture (Control); Organic rice in rotation with perennial Lucerne (2 years of rice + 2 years of Lucerne)
Cover crops	2. Loreto – Conventional grain corn in succession with legumes winter cover - Conventional grain corn with Forage Pea as a cover crop in winter; Conventional grain corn with Red Clover as a cover crop in winter; Conventional grain corn with Yellow Lupine as a cover crop in winter; Conventional grain corn with Balansa Clover as a cover crop in winter; Conventional grain corn with Arrowleaf Clover as a cover crop in winter; Conventional grain corn with no cover crop in winter (fallow- control)
Fertilisation/amendments	3. São Silvestre - Conventional grain corn fertilized by urban sludge - Grain corn receiving urban sludge fertilization; Grain corn receiving conventional mineral fertilization (control)

Study Site poster 2018; EGU 2019 Study Site poster (download)

SICS 1 :- Rotation system - Bico da Barca – Organic Rice in rotation with perennial lucerne (two years of rice + 2 years of Lucerne)

Read this fact sheet in Portuguese here

SICS1b

Key findings

SICS improves soil fertility in terms of soil organic matter content
SICS using the Nitrogen biological fixation avoid any mineral nitrogen fertilization and is a very conservative technic in term of nutrient leaching and groundwater pollution.
SICS does not increase weed burdens, thus leaving corn yields unaffected. Blind seeding and rotation with perennial lucerneare efficient techniques in terms of weed control, with a significant seed bank reduction.

SICS 2 :- Succession system - Loreto - Principal crop (grain corn ) integrated in a succession of legumes (clover, pea, trefoil….) used as green manure.

Read this fact sheet in Portuguese here

SICS4c

Key findings

In general, all six legume cover crops showed good adaptation to Mediterranean conditions, yielding large amounts of dry biomass (up to 8 ton/ha for some clovers species).
The overall median N-P-K nutrient uptake over the 2 study years considering all the species was 176-20-172 kg/ha with clover species presenting generally the best performances.
The capacity of the legume cover crops to provide green manure services enabled a general reduction of about 35% of N, 50% of P, and 100% of K supplied generally by mineral fertilizers for a grain corn production of 12t/ha.
Legume cover crops effectively controlled weeds, although only in the second year of the study. Three clover species (crimson, balansa, arrowleaf) performed best in terms of weed control due to early establishment and/or high biomass production in later growth stages, and thus continuous competition with weed species.
Legume cover crops incorporation into the soil leaded through the two years experiment to a slight depletion of the soil organic matter content generally more severe for the less fertile soils. However, large fluctuations in soil organic matter content in legume cover crops plots between soil sampling occasions were observed for the LCC plots, but not for the fallow control plot, reflecting important modifications in soil nutrient cycles due to incorporation of large LCC biomass with high decomposition potential.
No differences were found between treatments and in term of pH, Nitrogen, available phosphorus and potassium or exchange base (K+, Mg2+,Na+,ca2+), soil compatibility, infiltration capacity, or biodiversity (earthworm).

SICS 3 :- Organic fertilization system - São Silvestre - Organic fertilization system from urban origin (sewage sludge)

Read this fact sheet in Portuguese here

SICS3c

Key findings

After 3 consecutive years of urban sludge application in the agricultural field, soil fertility was significantly improved. Almost all the parameters analyses in this study show a positive impact of the urban sludge application. It improved pH, SOC content, Total Nitrogen, Available Phosphorus and Potassium, exchangeable cations (Ca2+ and K+) and also Earthworms density.
Under urban sludge application, extremely high values of Phosphorus and Potassium were identified, especially Phosphorus.
Under urban sludge application, any relevant increase of heavy metal concentration in the soil was identified. The concentrations maintained were much lower than the limits defined by the national law for sludge application or fertilizer application in general.

Geographical description

The study areas are located in the Lower Mondego river valley, an alluvium plane situated in Central Portugal. The valley is roughly east-west oriented and 40 km long (from the Coimbra city to the estuary near Figueira da Foz) and bordered by gently sloping hills. The floodplain covers about 15.000 ha of fertile land and has traditionally been used for irrigated agriculture.

The entire valley is between 0 and 25 meters above sea level. Soils are modern alluvial soils, with a texture from silt-loam to sandy-clay-loam. The climate is Mediterranean, characterized by rainy winters and dry summers, more precisely a Csa climate under the Köppen climate classification, " Hot-summer Mediterranean climate ". The annual average temperature is 16.1ºC, with smooth variations. The annual average precipitation is 922 mm, essentially concentrated between October and March.

The Baixo Mondego valley is mainly dedicated to a monoculture of irrigated corn grain and flooding rice. The eastern part is mainly used for corn, while the western area, closer to the river mouth, is used mainly for rice.

Map

Cropping systems

Conventional tillage is practised with various passes of heavy machinery. Disc harrow passes for straw stubble incorporation, furrow plough passes for soil inversion, chisel and rotary tiller passes to prepare seedbed.

In 1970, the hydro-agricultural exploitation project of the Mondego Valley started that affects about 12.300 ha (total irrigation perimeter). It considers the development and restructuration of the agricultural system which involves: property reparcelling, soil levelling and the creation of new irrigation and drainage systems. To date, about 6.700 ha are equipped. Irrigation is principally performed with surface furrow irrigation systems, by gravity fed. Soils are levelled and water flows passively on furrows opened between each line of maize. Compared to pressurized systems (sprinkler and drip), surface irrigation systems require lower capital investment. However, some farmers also use pivot irrigation systems.

Production is based on expensive production factors: mineral fertilizers to compensate for the important soil nutrient exportation after harvesting, pesticides for pest control problems driven by intensive monoculture.

Soil improving cropping system and techniques currently used

Concerning rice cropping systems, the DRAP-Centro is currently monitoring a long term experiment (for about 10 years) that involves a cropping system composed of organic rice in rotation with perennial lucerne (two years of rice followed by two years of lucerne). The introduction of a legume in the rotation provides an increase of the nitrogen available for rice production and is beneficial for pests and weeds control.

Concerning maize cropping systems, some farmers use organic amendments such as urban sludge, but it is a very controversial issue. A small number of farmers have introduced legumes or a mix of legumes and gramineous as cover crops during the winter, but it’s not a very common technique.

External drivers or factors

Institutional and political drivers

As previously stated, part of the SoilCare effort made by the Portuguese (ESAC) team will be a consequence of the implementation of the forthcoming new priorities set by the Common Agriculture Policy. In addition, the new reading made of the Water Framework Directive will imply an increase of the water price for agriculture.

Societal drivers

There is an ongoing tendency to shift from the traditional to the organic systems which is pushed by a younger and urban population fringe. This implies that the organic farming systems are gaining territory.

Bio-physical drivers

Being under a wet Mediterranean type of climate, the Portuguese study areas are affected by water shortages that occur during the vegetative growth season. The absence of proper irrigation systems and the proper water amounts for irrigation have an overwhelming effect on crop productivity.