{ "id": "soils-for-coffee", "url": "https://coffearium.org/entries/soils-for-coffee/", "license": "CC-BY-4.0", "title": "Soils for coffee", "summary": "What a soil has to offer coffee roots – depth, structure, drainage, water and organic matter – which soil types coffee grows on in Colombia, Brazil and Kenya, and how soil is sampled and tested.", "domain": "farm-management", "kind": "Concept", "stage": "farm", "topics": [ "science", "sustainability" ], "topicSections": { "sustainability": { "id": "compaction-cover-and-soil-carbon", "label": "Compaction, cover and soil carbon" } }, "lang": "en", "status": "verified", "reviewer": "Coffearium verification pass", "lastVerified": "2026-10-23T00:00:00.000Z", "updated": "2026-10-23T00:00:00.000Z", "added": "2026-10-23T00:00:00.000Z", "brief": [ "A coffee science textbook chapter states that coffee tolerates many soils if they are deep, porous and well drained; most arabica roots lie in the top 0.30 m.1,2", "In Colombia, 52% of coffee plantations stand on soils derived from volcanic ash, which are acid and rich in organic matter.4", "Coffee in the Brazilian Cerrado expanded mainly on Oxisols; two Kenyan reference profiles under coffee are deep, well-drained Nitisols.6,8,14", "Recommended soil pH differs by institute and country, for example 5.0–5.5 in Colombia (Cenicafé) and 6.0–6.5 on a Kerala Agricultural University page, India.3,10", "Colombian guidance samples soil under the trees to 20 cm, five to six subsamples per hectare mixed into one sample of about 1 kg.3" ], "quickFacts": [ { "label": "Main root zone (arabica)", "value": "Top 0.30 m; a circle about 1.50 m across around the stem" }, { "label": "Soil depth (robusta, FAO Ecocrop)", "value": "Optimum 50–150 cm; tolerates 20–50 cm" }, { "label": "Soils named in the sources", "value": "Andic soils from volcanic ash (Colombia); Oxisols (Brazilian Cerrado); Nitisols (Kenyan reference profiles)" }, { "label": "Recommended pH", "value": "5.0–5.5 (Cenicafé, Colombia); 6.0–6.5 (Kerala Agricultural University, India); 5–6.3 (Ecocrop, robusta)" }, { "label": "Organic matter, Colombian ash soils", "value": "Averages of 6–22% by soil unit" }, { "label": "Soil sample (Colombia)", "value": "0–20 cm under the trees; 5–6 subsamples per hectare; about 1 kg composite" } ], "aka": [ "Coffee soils", "Soil requirements of coffee" ], "linkTerms": [ "coffee soil", "soil requirements", "soil profile", "soil sample", "soil sampling", "soil analysis", "soil test", "Andosol", "Andisol", "Nitisol", "Oxisol", "Latossolo", "volcanic soils" ], "related": [ "site-selection-and-climate", "shade-and-agroforestry", "soil-acidity-and-liming", "nutrition-and-fertilisation", "planting-density-and-layout", "irrigation", "overbearing-and-dieback", "coffea-arabica", "coffea-canephora", "branching-and-fruiting-wood" ], "contested": [ "Soil iron and cup quality: in a 2016 Ethiopian study, higher available iron went with better grade and specialty quality11; in a 2015 study of 54 farms in Huila, Colombia, the abstract associates the cup-quality group with the lowest sensory scores with aluminium and iron in the soil, and the results text links that group to soils high in iron.12 Both studies are correlational, from one region each, and used different soil depths and quality scores.", "Recommended soil pH: Cenicafé in Colombia aims for 5.0–5.5 after liming3, an extension page of Kerala Agricultural University in India recommends 6.0–6.510, and FAO Ecocrop lists 5–6.3 as optimal for robusta.9 The ranges overlap only partly and come from different countries and species." ], "corrections": [ { "date": "2026-10-23T00:00:00.000Z", "change": "Soil classes: removed the claims that four WRB groups (incl. Ferralsols, Acrisols) \"matter for coffee\" and that coffee in Kenya grows on Nitisols in general; now limited to the two Kenyan reference profiles and to what the Brazilian and Colombian studies state.", "reason": "No source consulted links Ferralsols or Acrisols to coffee, equates WRB groups with Oxisols or Latossolos in general, or gives the share of Kenyan coffee on Nitisols." }, { "date": "2026-10-23T00:00:00.000Z", "change": "Huila study: the abstract's link of the lowest-scoring cups to aluminium and iron is now given with the paper's own results text, which links aluminium-rich soils to another group; noted the abstract–table mismatch in P for organic matter.", "reason": "The paper's abstract, results text and Table 3 disagree." }, { "date": "2026-10-23T00:00:00.000Z", "change": "Compaction study: the interrow was subsoiled about 14 months before sampling, not just before; \"bore the most load\" changed to \"highest load-bearing capacity\".", "reason": "Gontijo et al. 2008, material and methods." }, { "date": "2026-10-23T00:00:00.000Z", "change": "Kerala Agricultural University pH 6.0–6.5 is now given as that page's recommendation without a region; Colombian P and K critical levels marked as for new plantings.", "reason": "The page names no region or species; Sadeghian 2008 gives these levels for the vegetative stage." } ], "sources": [ { "id": "s1", "title": "Cultivating Coffee Quality – Terroir and Agro-Ecosystem", "authors": "Lambot, C.; Herrera, J. C.; Bertrand, B.; Sadeghian, S.; Benavides, P.; Gaitán, A.", "year": 2017, "publisher": "In: Folmer, B. (ed.), The Craft and Science of Coffee, Academic Press, ch. 2, pp. 17–49", "url": "https://doi.org/10.1016/B978-0-12-803520-7.00002-5", "doi": "10.1016/B978-0-12-803520-7.00002-5", "tier": "B", "tierNote": "Textbook chapter; used only for statements without numbers, attributed.", "quote": "Coffee trees tolerate a wide range of soils, provided that they are deep, porous, well drained, and well balanced for their texture.", "quotes": [], "accessed": "2026-10-23T00:00:00.000Z" }, { "id": "s2", "title": "Ecophysiology of coffee growth and production", "authors": "DaMatta, F. M.; Ronchi, C. P.; Maestri, M.; Barros, R. S.", "year": 2007, "publisher": "Brazilian Journal of Plant Physiology 19(4), 485–510", "url": "https://scielo.br/j/bjpp/a/xSBXnvrDDczyDbBtzspGs3v", "doi": "10.1590/S1677-04202007000400014", "tier": "A", "quote": "The main part of the root system of an arabica coffee tree is generally concentrated in the first 0.30 m layer", "quotes": [], "accessed": "2026-10-23T00:00:00.000Z" }, { "id": "s3", "title": "Fertilidad del suelo y nutrición del café en Colombia: guía práctica", "authors": "Sadeghian Khalajabadi, S.", "year": 2008, "publisher": "Cenicafé, Boletín Técnico 32", "url": "https://www.cenicafe.org/es/publications/bot032.pdf", "tier": "A", "tierNote": "Technical bulletin of the Colombian national coffee research centre (own research publication).", "quote": "Las muestras deben tomarse en el plato del árbol, a 20 cm de profundidad.", "quotes": [], "accessed": "2026-10-23T00:00:00.000Z" }, { "id": "s4", "title": "Propiedades de la materia orgánica y capacidad complejante sobre el aluminio en algunos suelos ándicos en Colombia", "authors": "Ortiz-Escobar, M. E.; Zapata-Hernández, R. D.; Sadeghian-Khalajabadi, S.", "year": 2006, "publisher": "Cenicafé 57(1), 51–57", "url": "https://www.cenicafe.org/es/publications/arc057%2801%29051-057.pdf", "tier": "A", "quote": "En Colombia, el 52% de los cafetales se encuentran establecidos en suelos derivados de ceniza volcánica", "quotes": [], "accessed": "2026-10-23T00:00:00.000Z" }, { "id": "s5", "title": "World Reference Base for Soil Resources. International soil classification system for naming soils and creating legends for soil maps. 4th edition", "authors": "IUSS Working Group WRB", "year": 2022, "publisher": "International Union of Soil Sciences (IUSS), Vienna", "url": "https://files.isric.org/public/documents/WRB_fourth_edition_2022-12-18.pdf", "tier": "A", "quote": "Low-activity clays, P fixation, many Fe oxides, strongly structured", "quotes": [], "accessed": "2026-10-23T00:00:00.000Z" }, { "id": "s6", "title": "Chemical and hydrophysical attributes of an Oxisol under coffee intercropped with brachiaria in the Cerrado", "authors": "Rocha, O. C.; Ramos, M. L. G.; Veiga, A. D.; Guerra, A. F.; Bartholo, G. F.; Rodrigues, G. C.; Silva, J. E. da", "year": 2016, "publisher": "Pesquisa Agropecuária Brasileira 51(9), 1476–1483", "url": "https://scielo.br/j/pab/a/QNCZnm5vBpSx9G6sWRTBnrt/?lang=en", "doi": "10.1590/S0100-204X2016000900046", "tier": "A", "quote": "The development and expansion of the coffee crop in the Cerrado occurred predominantly in Oxisols", "quotes": [], "accessed": "2026-10-23T00:00:00.000Z" }, { "id": "s7", "title": "Atributos físico-hídricos de um latossolo de cerrado em diferentes posições de amostragem na lavoura cafeeira", "authors": "Gontijo, I.; Dias Junior, M. S.; Guimarães, P. T. G.; Araujo-Junior, C. F.", "year": 2008, "publisher": "Revista Brasileira de Ciência do Solo 32(6), 2227–2234", "url": "https://www.redalyc.org/pdf/1802/180214064002.pdf", "tier": "A", "quote": "The soil load support capacity under MN and PS was homogeneous, indicating a soil structure favorable", "quotes": [], "accessed": "2026-10-23T00:00:00.000Z" }, { "id": "s8", "title": "Reference soil Kenya 44: Nitisol", "authors": "Kenya Soil Survey", "publisher": "ISRIC World Soil Museum", "url": "https://museum.isric.org/node/1061", "tier": "A", "tierNote": "Reference soil profile description from a national soil survey, held by ISRIC.", "quote": "The soil is used for arable farming with crops as coffee, maize, bananas and cassava.", "quotes": [], "accessed": "2026-10-23T00:00:00.000Z" }, { "id": "s9", "title": "Ecocrop data sheet: Coffea canephora", "authors": "FAO", "publisher": "FAO Ecocrop database", "url": "https://ecocrop.apps.fao.org/ecocrop/srv/en/dataSheet?id=750", "tier": "A", "tierNote": "FAO database of crop environmental requirements compiled from the literature; A for the values it lists.", "quote": "medium (50-150 cm)", "quotes": [], "accessed": "2026-10-23T00:00:00.000Z" }, { "id": "s10", "title": "Coffee: climate and soil", "authors": "Centre for E-Learning, Kerala Agricultural University", "publisher": "Kerala Agricultural University, Information Gateway on Agriculture", "url": "https://www.celkau.in/crops/Plantation%20Crops/Coffee/climate_and_soil.aspx", "tier": "A", "tierNote": "University extension page (India); A only for its own recommendation, given attributed. The page names no region or species for the pH value.", "quote": "The soil should be deep, friable, and rich in organic matter with a pH of 6.0-6.5.", "quotes": [], "accessed": "2026-10-23T00:00:00.000Z" }, { "id": "s11", "title": "Association of Arabica Coffee Quality Attributes with Selected Soil Chemical Properties", "authors": "Mintesnot, A.; Dechassa, N.; Mohammed, A.", "year": 2016, "publisher": "East African Journal of Sciences (Haramaya University)", "url": "https://eajs.haramayajournals.org/index.php/eajs/article/view/277", "tier": "A", "quote": "The soil CEC and available soil iron (Fe) accounted for 13 and 21.9%, respectively of the observed variation", "quotes": [], "abstractOnly": true, "accessed": "2026-10-23T00:00:00.000Z" }, { "id": "s12", "title": "Effect of culture conditions, the chemical characteristics of soil and grain handling in the sensory attributes of coffee (Coffea arabica L.) in cup", "authors": "Suárez Salazar, J. C.; Rodríguez Burgos, E.; Duran Bautista, E. H.", "year": 2015, "publisher": "Acta Agronómica 64(4), 329–335", "url": "https://revistas.unal.edu.co/index.php/acta_agronomica/article/download/44641/55942/290656", "doi": "10.15446/acag.v64n4.44641", "tier": "A", "quote": "Q1 that had low scores on the sensory attributes was associated to soil characteristics such as Al and Fe.", "quotes": [], "accessed": "2026-10-23T00:00:00.000Z" }, { "id": "s13", "title": "Expected global suitability of coffee, cashew and avocado due to climate change", "authors": "Grüter, R.; Trachsel, T.; Laube, P.; Jaisli, I.", "year": 2022, "publisher": "PLoS ONE 17(1), e0261976", "url": "https://doaj.org/article/012401b6f96a47b0a536a8ff14b0ff51", "doi": "10.1371/journal.pone.0261976", "tier": "A", "quote": "were more restrictive for the global extent of suitable growing regions than land and soil parameters", "quotes": [], "abstractOnly": true, "accessed": "2026-10-23T00:00:00.000Z" }, { "id": "s14", "title": "Reference soil Kenya 01: Nitisol", "authors": "Kenya Soil Survey (Rachilo; Michieka)", "publisher": "ISRIC World Soil Museum", "url": "https://museum.isric.org/node/1084", "tier": "A", "tierNote": "Reference soil profile description from a national soil survey, held by ISRIC.", "quote": "well-drained, very deep, dark reddish brown to dark red, friable clay", "quotes": [], "accessed": "2026-10-23T00:00:00.000Z" } ], "markdown": "## What coffee roots need from a soil\n\nSoil holds the tree up and stores the water and nutrients its roots take in. A coffee science textbook chapter states that coffee tolerates many soils, provided they are deep, porous, well drained and well balanced in texture.1 Texture means the mix of sand, silt and clay particles. The same chapter describes volcanic soils as particularly well suited.1\n\nMost coffee roots stay near the surface. In arabica coffee, the main part of the root system lies in the top 0.30 m of soil.2 It spreads over a circle about 1.50 m across around the stem.2 Conilon, a group of robusta, seems to follow a similar pattern.2 Root depth and length change with soil characteristics, plant age, planting density and variety.2 How the stem and branches grow above ground is covered in branching and fruiting wood.\n\nA 2022 global suitability study of coffee, cashew and avocado found climate factors more limiting than land and soil factors for all three crops.13 On the soil side, low pH, poor texture and steep slopes mattered most.13\n\n
\n
\n
    \n
  1. Leaf litter: fallen leaves of shade trees act as a mulch and add organic matter.1
    2. \n
  2. Topsoil: the dark upper layer, where most roots are; in Colombian ash soils, organic matter averages 6–22% by soil unit.2,4
    3. \n
  3. Subsoil: in a Kenyan Nitisol profile, a very deep, well-drained, friable dark red clay.14
    4. \n
  4. Parent material: the weathering rock the soil forms from, for example basic volcanic breccia under a Kenyan Nitisol.8
    5. \n
  5. Main root mass: mostly in the top 0.30 m, spread over a circle about 1.50 m across (arabica).2
    6. \n
  6. Deeper roots: after a long dry period in Kenya, root activity was greatest at 0.45–0.75 m, near the stem.2
    7. \n
  7. Soil sample: in Colombian guidance, taken under the trees to 20 cm.3
    8. \n
\n
A soil profile under a coffee tree. Layer depths are schematic; root depths follow a 2007 review. Schematic, not to scale.2,3,8
\n
\n\n## Depth, structure, drainage and water\n\n**Depth.** The FAO Ecocrop database lists a medium soil depth of 50–150 cm as optimal for robusta.9 It lists shallow soils of 20–50 cm as the limit the crop still tolerates.9 No comparable database entry for arabica was consulted for this entry.\n\n**Structure and pores.** Structure is the way soil particles clump into crumbs and blocks, leaving pores between them. Pores hold water and air and give roots a path. In an Oxisol under coffee in the Brazilian Cerrado, pores made up 0.61 m³ per m³ of soil. Large pores made up 0.21 m³ per m³.6 Wheels and machines compact soil, which can damage its structure and lower coffee production.7\n\n**Drainage.** Water must drain away so that roots get air. Ecocrop lists well-drained soil as optimal for robusta.9 The textbook chapter gives good drainage as a condition for coffee in general.1\n\n**Water holding.** How much rain coffee needs depends partly on how much water the soil retains.2 In the Cerrado study, a grass grown between the rows improved the soil properties linked to water supply for coffee.6 Irrigation itself is covered in [Irrigation](/entries/irrigation/).\n\n## Typical coffee soils\n\nSoil scientists name soils by their main properties. The international system, the World Reference Base (WRB), groups them into reference soil groups.5 National studies often use other systems, such as the Brazilian classes (Latossolos) or Oxisols, and the sources consulted here do not equate these classes in general. Two WRB groups appear in the coffee sources of this entry:\n\n- **Andosols** are marked by allophanes or aluminium–humus complexes.5 Colombian coffee studies speak of andic soils, or Andisols, derived from volcanic ash; they do not give a WRB group.3,4\n- **Nitisols** have low-activity clays, many iron oxides and a strong structure, and they bind phosphorus.5 Two Kenyan reference profiles under coffee are Nitisols.8,14\n\n**Colombia.** In Colombia, 52% of coffee plantations stand on soils derived from volcanic ash.4 These soils are acid, with a pH below 5.5, and rich in organic matter.4 Their dry soil is light: about 0.7 g per cm³, half the 1.4 g per cm³ of a sandy soil in Tolima.3\n\n**Brazil.** Coffee in the Cerrado, the savanna of central Brazil, expanded mainly on Oxisols.6 Oxisols cover more than half of the Cerrado.6 The soil of that study is a Latossolo Vermelho in the Brazilian system, which the authors give as a Typic Haplustox.6 One studied plantation in Patrocínio, Minas Gerais, grows on a red Latossolo.7\n\n**Kenya.** Two Kenyan reference profiles held by ISRIC are Nitisols linked to coffee.8,14 One, used for coffee, maize, bananas and cassava, is very deep, well drained and derived from basic volcanic breccia.8 The other, at about 1,700 m east of the Rift Valley, grew arabica coffee before its present crops.14 No source consulted here gives the share of Kenyan coffee on Nitisols.\n\n**Where the species come from.** According to the textbook chapter, wild robusta grows mainly on red, acidic, well-drained soils of low natural fertility.1 Wild arabica in Ethiopia grows on deep, red or brownish, well-drained soils.1\n\n## Soil pH in brief\n\nSoil pH measures how acid a soil is. Recommended ranges for coffee differ by country and species (see Contested).3,9,10 The Colombian research centre Cenicafé recommends liming to raise soil pH to 5.0–5.5 and lower exchangeable aluminium below 1.0 cmol(+)/kg.3 An extension page of Kerala Agricultural University in India recommends pH 6.0–6.5, without naming a region or species.10 Why acidity matters, aluminium toxicity and how lime is applied are covered in [Soil acidity and liming](/entries/soil-acidity-and-liming/).\n\n
\n
\n
Recommended soil pH for coffee from three sources, and pH described or measured in Colombian coffee soils. Recommendations differ by country and species. Data: Sadeghian; Ortiz-Escobar et al.; FAO Ecocrop; Kerala Agricultural University; Suárez Salazar et al.3,4,9,10,12
\n
\n\n## How soil is sampled and tested\n\nA soil test tells a producer what the soil holds before fertiliser is bought. According to the textbook chapter, training programmes recommend that producers have soil samples analysed by a competent laboratory before buying fertiliser.1\n\nColombian guidance from Cenicafé describes the sampling step by step:3\n\n1. Take samples under the trees, to a depth of 20 cm.3\n2. Walk the lot in a zigzag and take five to six subsamples per hectare.3\n3. Mix them into one composite sample of about 1.0 kg.3\n4. Sample at least 3–4 months after the last fertiliser application.3\n\nThe bulletin interprets soil pH, organic matter, exchangeable aluminium and nutrients such as phosphorus, potassium and magnesium.3 Cenicafé compares each value with a critical level and sets fertiliser doses from it.3 How those doses are worked out belongs to [Nutrition and fertilisation](/entries/nutrition-and-fertilisation/).\n\n\n\n## Roots in the profile\n\nRoot activity moves through the profile with the seasons. In a Kenyan study cited in a 2007 review, arabica root activity after a long dry period was greatest at 0.45–0.75 m depth, close to the stem.2 After rain, activity was greatest at the soil surface, 0.70 m from the stem.2 In dense plantings, roots grow deeper and take up water and nutrients from lower soil horizons.2\n\nRoot growth is seasonal and often starts before shoot growth.2 Heavy crops may seriously impair root function.2 Branch die-back is preceded by the death of a large share of the absorbing roots.2 This link is covered in [Overbearing and dieback](/entries/overbearing-and-dieback/).\n\nWhere the absorbing roots sit also decides where soil is sampled. In a Brazilian plantation, most absorbing roots were found under the canopy.7 Colombian guidance samples the same zone under the trees.3\n\n## Soil mass and what a test value means\n\nA laboratory reports a concentration, such as milligrams of phosphorus per kilogram of soil. The amount per hectare depends on how much soil the roots explore. In the Colombian coffee zone, the top 20 cm of one hectare weighs between 1,400,000 and 2,800,000 kg.3 The range follows from the dry soil density, from about 0.7 g per cm³ in Andisols to 1.4 g per cm³ in a sandy soil.3\n\nAs a worked example, take the Cenicafé critical level for phosphorus at one crop stage, 30 mg/kg.3 In the lightest soil, that is 42 kg of phosphorus per hectare in the top 20 cm; in the heaviest, 84 kg (our calculation, from the soil masses above). The same test value therefore stands for different stocks in different soils.\n\n## Organic matter\n\nAccording to the textbook chapter, farming should preserve and if possible increase soil organic matter, to support microbial life and the soil's exchange capacity.1 Exchange capacity is the soil's ability to hold nutrient cations such as potassium, calcium and magnesium.\n\nMeasured values differ widely between coffee soils. In Colombian soils from volcanic ash, organic matter averaged 18% in the soil units CH and TI, 22% in PI and 6% in MN.4 That study examined how this organic matter binds aluminium.4 On 54 farms in Huila, Colombia, the mean organic matter of four soil types ranged from 3.54% to 5.13% in samples to 15 cm.12 The paper's table gives P = 0.0054 for this difference, while its abstract reports P < 0.001.12 Cenicafé treats organic matter below 6% as very low and then recommends decomposed coffee pulp or other organic amendments.3\n\n
\n
\n
Soil organic matter in two Colombian studies: soil units derived from volcanic ash, and four soil types on 54 farms in Huila. Sampling depths differ. Data: Ortiz-Escobar et al.; Suárez Salazar et al.4,12
\n
\n\n## Compaction, cover and soil carbon\n\nMechanised plantations compact their soil where wheels run. A 2008 study in Patrocínio, Minas Gerais, sampled a red Latossolo under coffee planted at 4 × 1 m in 1995.7 It compared the cart track, the soil under the canopy, the middle of the interrow and native Cerrado vegetation.7 The cart track had the highest load-bearing capacity; the interrow, subsoiled about 14 months before sampling, was the most susceptible to compaction.7 Soil under the canopy behaved like the native soil, with a structure favourable to root growth.7\n\nGround cover changes the topsoil too. In a 2016 Cerrado trial, irrigated coffee with a brachiaria grass grown between the rows gave higher yields.6 Irrigation favoured organic carbon stocks in the upper soil layers, while brachiaria favoured the physical properties linked to water availability.6\n\nAccording to the textbook chapter, soil erosion rates vary widely between coffee farms, and most farms lose soil faster than is optimal.1 No study consulted for this entry measured erosion on coffee farms; soil conservation will be covered in a planned entry, Land preparation and soil conservation.\n\n## Soil and cup quality\n\nOnly a few studies have tested soil against cup quality directly, and they are correlational. According to the textbook chapter, depleted soils go with lower coffee quality, and the most acidic coffees come from volcanic soils.1\n\n**Ethiopia, 2016.** A study paired 53 soil samples, taken at 0–50 cm near the trunks, with the coffee from the same places in the 2010/11 harvest.11 Quality correlated positively with cation exchange capacity (r = 0.36), available magnesium (r = 0.28), exchangeable acidity (r = 0.35) and soil pH (r = 0.30).11 It correlated negatively with available copper (r = −0.35), zinc (r = −0.40) and total nitrogen (r = −0.40).11 Available iron and exchange capacity explained 21.9% and 13% of the variation in overall quality.11\n\n**Huila, Colombia, 2015.** A study of 54 farms in Suaza and Timaná related soil, crop management and processing to cup quality.12 The four soil types differed significantly in pH, calcium, magnesium, base saturation, aluminium, phosphorus and zinc.12 The abstract associates the cups with the lowest sensory scores with aluminium and iron in the soil.12 The results text is not fully consistent with this: it links the low-scoring group to moderately acid soils high in iron, copper, zinc and sulphur, and very acid soils high in aluminium to the group associated with body, sweetness, balance, flavour and acidity.12 The results text also links iron-rich, very acid soils to a third group, so the paper gives no consistent soil signal for the lowest-scoring cups. Fermentation time and shade management also entered the groups, so soil is one factor among several.12\n\nThe two studies point in different directions for iron (see Contested). Neither controls for altitude, variety and processing the way a designed trial would. No study consulted for this entry shows that changing a soil property changes cup quality.\n\n## Reference values\n\n| Parameter | Value | Context | Source |\n|---|---|---|---|\n| Main root zone (arabica) | Top 0.30 m; circle ≈1.50 m across | General; conilon similar | DaMatta et al.2 |\n| Deeper root activity after drought | 0.45–0.75 m, near the stem | Arabica, Kenya | DaMatta et al.2 |\n| Soil depth (robusta) | Optimum 50–150 cm; tolerated 20–50 cm | FAO Ecocrop | FAO9 |\n| Salinity (robusta) | Low, below 4 dS/m | FAO Ecocrop | FAO9 |\n| Soil pH, recommended | 5.0–5.5 after liming | Colombia, Cenicafé | Sadeghian3 |\n| Soil pH, recommended | 6.0–6.5 | Extension page, India; no region or species named | Kerala Agricultural University10 |\n| Soil pH, optimum (robusta) | 5–6.3 (absolute 4–8) | FAO Ecocrop | FAO9 |\n| Exchangeable aluminium, target | Below 1.0 cmol(+)/kg | Colombia, after liming | Sadeghian3 |\n| Critical phosphorus | 30 mg/kg | Colombia, new plantings (vegetative stage) | Sadeghian3 |\n| Critical potassium | 0.40 cmol(+)/kg | Colombia, new plantings | Sadeghian3 |\n| Low magnesium | Below 0.9 cmol(+)/kg | Colombia | Sadeghian3 |\n| Ideal Ca:Mg:K ratio | 6:2:1 | Colombia; no critical levels for ratios | Sadeghian3 |\n| Organic matter, very low | Below 6% | Colombia | Sadeghian3 |\n| Organic matter, measured | 6–22% (averages by soil unit) | Colombian ash soils | Ortiz-Escobar et al.4 |\n| Organic matter, measured | 3.54–5.13% (means of four soil types, 0–15 cm) | Huila, Colombia | Suárez Salazar et al.12 |\n| Dry soil density | ≈0.7 g/cm³ (Andisols) to 1.4 g/cm³ (sandy soil) | Colombia | Sadeghian3 |\n| Total porosity; macroporosity | 0.61 and 0.21 m³/m³ | Oxisol, Cerrado, Brazil | Rocha et al.6 |\n| Sampling | 0–20 cm under the trees; 5–6 subsamples/ha; ≈1.0 kg composite; ≥3–4 months after fertiliser | Colombia | Sadeghian3 |\n\n## Open questions\n\n- **Arabica soil limits in a database.** No database or institute value for the soil depth arabica needs was consulted for this entry; the depth values above are for robusta.9\n- **One pH target.** Recommended ranges differ between Colombia, India and the Ecocrop database, and no study consulted here compared yields across pH in several countries.3,9,10\n- **Soil and the cup.** The two cup-quality studies are correlational and disagree on iron.11,12 A designed trial that changes one soil property and scores the cup was not found.\n- **Shares of soil groups.** Apart from the Colombian 52% on ash soils, no source consulted here gives the share of coffee land on each soil group by country.4\n\n## Key studies\n\n
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Ortiz-Escobar et al., 2006 – Organic matter in Colombian ash soils. Studied the organic matter of andic soils in the Colombian coffee zone and its capacity to bind aluminium. Reports that 52% of Colombian coffee stands on soils from volcanic ash, acid and rich in organic matter, with averages of 6–22% by soil unit.

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Cenicafé 57(1), 51–57 · cenicafe.org

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Rocha et al., 2016 – Oxisol under coffee and brachiaria. Measured carbon, nitrogen and physical properties of a Cerrado Oxisol under coffee managed with irrigation and with brachiaria between the rows. Irrigation favoured carbon in the upper layers; the grass favoured properties linked to water supply.

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Pesquisa Agropecuária Brasileira 51(9), 1476–1483 · doi:10.1590/S0100-204X2016000900046

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Gontijo et al., 2008 – Compaction in a coffee Latossolo. Modelled the load a red Latossolo can bear at four positions in a plantation in Minas Gerais. The cart track had the highest load-bearing capacity, the subsoiled interrow the lowest, and soil under the canopy kept a structure favourable to roots.

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Revista Brasileira de Ciência do Solo 32(6), 2227–2234 · redalyc.org

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Mintesnot et al., 2016 – Soil chemistry and Ethiopian coffee quality. Correlated soil chemical properties of 53 samples with grade and specialty quality. Exchange capacity, magnesium and pH correlated positively; zinc, copper and total nitrogen negatively; available iron explained 21.9% of the variation in quality.

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East African Journal of Sciences · eajs.haramayajournals.org

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Suárez Salazar et al., 2015 – Soil, management and the cup in Huila. Related soil chemistry, crop management and processing on 54 farms to sensory scores with multivariate methods. Soil types differed strongly in pH and aluminium; the abstract associates the lowest-scoring cups with aluminium and iron, while the results text links aluminium-rich soils to a better group.

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Acta Agronómica 64(4), 329–335 · doi:10.15446/acag.v64n4.44641

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