Farm soils

🟫 Farm soils

What kind of ground lies under the crops: whether it is clayey, loamy or sandy, what type of soil it is, whether it is calcareous or acidic and how much organic matter it holds. Everything is measured over farmland (243 thousand km² in Spain, almost half the country) in the layer that gets worked, the top 30 cm, and matched with what is grown on top. Choose a region, a province or a municipality and the whole page, maps included, switches to that area; the page link changes with your choice so you can share it. The data come from a model (SoilGrids), not from tests of each field: they are good for comparing areas.

Spain

The dot map

Each dot is a square with farmland (10 km across for the whole of Spain, 5 km in a region, 2 km in a province and 250 m in a municipality), coloured by the texture, soil type or crop that covers the most farmland in it. Where there is no dot there is woodland or scrub, rock, water or town.

Clayey, loamy and sandy

Texture is the mix of clay, silt and sand in the ground, and it is the first thing a farmer looks at: a clayey soil ("heavy") holds water and nutrients but gets waterlogged, cracks and is hard to plough; a sandy one ("light") is easy to work and warms up earlier in spring, but water and fertiliser drain away; a loamy soil, with the three in balance, is ideal for almost everything. The farm soil of Spain averages 26 % clay, 37 % silt and 37 % sand.

Classes from the soil texture triangle of the US Department of Agriculture (USDA), the ones farm laboratories use in Spain. SoilGrids is a model that smooths out the extremes: very clayey ground (the bujeos, heavy black clays of the Guadalquivir countryside, or the tierras de barro, "mud lands", of Tierra de Campos) shows up as clay loam, and very sandy ground as sandy loam. That is why there are few pure clay or sand classes, and clay loams and clays are best read together as "heavy soils".

Soil types

Besides texture, soil scientists classify soils by how they formed. In the international classification (WRB, from the FAO), Spain's farmland is mostly Luvisols (old soils with clay built up at the bottom, like the red soils of La Mancha and Extremadura), Cambisols (young, little-developed soils), Calcisols (with a layer of limestone, typical of dry Spain), Leptosols (thin soils over rock, on slopes) and Vertisols (clays that swell when wet and crack when they dry, the "black soils" of the Andalusian countryside).

pH and organic matter

54 % of Spain's farmland is alkaline or calcareous (pH 7.5 or higher), against 15 % in the EU: limestone and gypsum underground and scarce rain, which does not wash the salts away, push the pH up. Only the Cantabrian coast, Galicia and the granite and slate west (Salamanca, Cáceres) have acidic soils.

Organic matter (decomposed remains of plants, roots and manure) gives the soil structure, holds water and feeds the crops. With heat, little rain and centuries of ploughing, Spanish farm soil averages 3.4 %, against 5.5 % in the EU. It ranks no. 3 poorest of the 36 European countries compared (the three with the least: Chipre, Hungría, España).

The laboratory samples of the European LUCAS programme (2018) show less organic matter than the model: on the farmland of España, the median of its 2,469 samples is 2.1 %, and 46 % are below 2 % (13 % below 1 %). For organic matter, trust these tests more than the map: SoilGrids gives more carbon than is measured in rain-fed land.

Erosion

Every year rain washes away the fertile layer of fields on slopes, above all ploughed ones, left without plant cover and hit by heavy storms: a centimetre of soil takes centuries to form. According to the model of the European Commission's Joint Research Centre, the farmland of España loses an average of 4.6 tonnes of soil per hectare per year (2016; Spain: 4.6), and 27 % suffers moderate or severe erosion, more than 5 t/ha, which is more than the soil can rebuild.

Erosion estimated with the JRC's RUSLE model (rainfall, slope, soil, crop and conservation practices) for farmland and natural grassland, published by Eurostat; the Balearic and Canary Islands are counted in their province. The signs seen in the field by LUCAS surveyors in 2018 (within 500 m of the point) point the same way: they appear at 8 % of the farmland points of España and there are gullies at 2.6 %; that is a minimum, because a grown crop hides many signs.

Comparing within the area

Provinces of Spain. Click one to see that province's soil here, with the map of its municipalities.

Heavy soils = the six clay loam and clay textures of the USDA triangle (generally more than a quarter clay). For municipalities, farmland and soil come from each 250 m cell within the municipality (CORINE and SoilGrids at their original resolution). Ceuta and Melilla have almost no farmland.

Which soil each crop sits on

Farmland is split according to the CORINE 2018 land-use map. Each crop sits on a different kind of ground: in Spain, dehesa wood-pastures are on the sandy, acidic soils of the west; olive groves and irrigated land on the most clayey soils of the valleys; vineyards on the most calcareous and poorest soils.

Crops from CORINE Land Cover 2018: rain-fed = arable land without irrigation (cereals, sunflower, pulses); irrigated = permanently irrigated arable land (maize, vegetables, cotton...); fruit trees include citrus, almonds and nuts; mixed = small plots of different crops side by side, market gardens and crops mixed with natural vegetation; dehesa = holm oak or cork oak woodland with pasture or crops underneath. CORINE does not map plots under 25 ha, which are added to whatever surrounds them.

Compared with Europe

Same method for every country: the SoilGrids model over CORINE 2018 farmland.

Cyprus, Greece, Spain, Italy and Turkey have the most alkaline farm soils, and Chipre, Hungría, España those with the least organic matter; the north (Ireland, the Nordic countries, the United Kingdom, the Netherlands) has the most acidic and organic ones, with wet meadows and, in some, peat. Countries with at least 1,000 km² of farmland in CORINE (excluding Malta). Below, the LUCAS laboratory samples, which confirm Spain's position.

LUCAS 2018 TOPSOIL (JRC): 0-20 cm samples from cropland and grassland tested in the laboratory; countries with 20 samples or more. As tests rather than a model, they show less organic matter than SoilGrids in southern Europe.

Europe on the map

The same layers for the whole of Europe, with 25 km cells and the same method as in Spain.

Each dot is a 25 × 25 km square with at least 25 km² of farmland according to CORINE 2018, with the soil from SoilGrids. The LUCAS laboratory samples are not drawn one by one: the JRC supplies them under terms of use that do not allow publishing them point by point; below they are summarised by region.

Region by region

Comparing whole countries hides a lot: northern Italy is nothing like the south, nor Andalusia like Galicia. Here, each European region (NUTS 2) with the model, what LUCAS measured where there are at least 10 samples, and the estimated erosion.

2021 NUTS 2 regions (boundaries © EuroGeographics). LUCAS uses the 2016 ones: the few regions that changed between the two versions have no measured figure. Erosion: latest year published by Eurostat.

The list is headed by countries with mountains and plenty of rain (Slovenia, Italy, Austria). Spain is in the upper half: its fields are hit by storm rains, slopes, and olive groves and vineyards with bare soil between the rows. In 2000, 31 % of its farmland had moderate or severe erosion, and in 2016, 27 %.

Sources and notes

• Soil: SoilGrids 2.0 (ISRIC - World Soil Information, CC BY 4.0 licence). Clay, silt and sand, pH in water and organic carbon of the 0-5, 5-15 and 15-30 cm layers (1 km averages for Spain, regions, provinces and Europe, and the original 250 m resolution for municipalities), weighted by thickness; most likely WRB soil group. It is a machine-learning model trained on thousands of soil profiles and satellite, climate and terrain maps: it smooths out the extremes and can be wrong for a particular district. Organic matter = organic carbon × 1.724.
• Farmland and crops: CORINE Land Cover 2018 (Copernicus, European Environment Agency), agricultural classes (2xx), sampled every 250 m.
• Borders: GISCO (Eurostat) for countries and the IGN (Spain's National Geographic Institute) for provinces.
• Laboratory samples: LUCAS 2018 TOPSOIL (European Soil Data Centre, ESDAC, esdac.jrc.ec.europa.eu, European Commission, Joint Research Centre). About 19,000 samples of 0-20 cm from across the EU tested in the laboratory; here, medians and percentages for cropland and grassland by country and by region with 10 samples or more (no Canary Islands). Panagos, P. et al. (2022), 'European Soil Data Centre 2.0', European Journal of Soil Science 73(6), e13315.
• Erosion: Eurostat, aei_pr_soiler, soil loss by water estimated by the Joint Research Centre with the RUSLE model (rainfall, slope, soil, cover and conservation practices) in 2000, 2010, 2016 and 2023, for farmland and natural grassland, by country, region and province (Panagos, P. et al. (2015), 'The new assessment of soil loss by water erosion in Europe', Environmental Science & Policy 54).
• Regions of Europe: GISCO (Eurostat), 2021 NUTS 2 regions (boundaries © EuroGeographics).
• Everything is calculated on a 1 × 1 km grid (250 × 250 m for municipalities) in an equal-area projection (ETRS89-LAEA), so every km² carries the same weight. Soil maps have no historical series: they are a snapshot of today's soil.

Data updated 7 minutes ago