IC Potash — Intercontinental Potash — Technical Presentation
77 slides from IC Potash's technical presentation
Slide 1: Polyhalite as a fertilizer: Technical Review
Polyhalite as a fertilizer Technical Review including review of literature for possible implications Intercontinental Potash 1
Slide 2: Potash - An Indispensable Product
Potash - An Indispensable Product ♦ Potassium (potash) is one of three nutrients essential for plant growth – It is a high concentration potassium mineral ♦ Polyhalite is a potassium mineral ♦ 95% of all production used in agriculture fertilizer ♦ Potash fertilizer increases crop yields and disease
Slide 3: Potash Usage - Expected to Increase
Potash Usage - Expected to Increase ♦ Growing population / incomes driving up global food demand ♦ Livestock feed, food crops and bio-fuels increasing fertilizer use ♦ Potash demand projected to increase through 2020 ♦ Current Market 50 million tons; growing at 3-4 % 3
Slide 4: Potash Usage - Expected to Increase
Potash Usage - Expected to Increase 4
Slide 5: Advantages of Polyhalite - No Chlorides
Advantages of Polyhalite - No Chlorides ♦ No Chloride ♦ Chloride sensitive crops include potatoes, tobacco, grapes, and tree fruits and vegetables ♦ Initial markets will be the no-Chloride Potassium fertilizer market: ♦ Potassium sulphate ♦ Potassium Nitrate ♦ Langbeinite 5
Slide 6: The Macronutrients for Agriculture
The Macronutrients for Agriculture ♦ There are six plant macronutrients ♦ The four natural salt macronutrients are ♦ Potassium, ♦ Sulfur ♦ Calcium ♦ Magnesium ♦ Polyhalite contains Potassium, Sulphur, Magnesium and Calcium 6
Slide 7: Advantages of Polyhalite - Multi-nutrient
Advantages of Polyhalite - Multi-nutrient ♦ Multi-nutrient Fertilizer ♦ Contains Potassium, Magnesium, Calcium, Sulphur ♦ Therefore this mineral fertilizer should be valuable in highly leached soils ♦ This product should be of value in areas which are heavily leached through having acid soils or low
Slide 8: Advantages of Polyhalite – A likely slow release product
Advantages of Polyhalite – A likely slow release product ♦Less soluble than Sylvite, Langbeinite, Potassium Sulphate ♦ Therefore will be a successful slow release fertilizer ♦ Slow release fertilizers are used in order to minimize leaching and wasting and therefore this product should be a cost effe
Slide 9: Potassium Minerals and Products
Potassium Minerals and Products ♦The marketed products are ♦ Potassium chloride ♦ Potassium sulphate ♦ Potassium magnesium sulphates of variable composition produced from kainite and langbeinite ores. ♦According to US Department of Agriculture Data the size of the non- potash Potassium market has in
Slide 10: Potassium Minerals and Products (% Nutrients)
Potassium Minerals and Products (% Nutrients) Mineral/Product K2O K S Mg Ca Cl Sylvite (Mineral) 63 .18 52.45 - - - 47.55 KCl SOP (Product) 50 44.87 18.4 - - 0 (K2SO4) Langbeinite (Mineral) 22.70 18.84 23.18 11.71 - 0 (K2SO4MgSO4 Polyhalite (Mineral) 15.66 12.97 21.27 4.03 13.29 - (K2MgCa2(SO4)42H2O
Slide 11: Forms in which Sylvite is used
Forms in which Sylvite is used ♦ Production as coarse, granular, standard, fine, suspension, soluble ♦ Bulk blend mixtures (DAP, ammonium nitrate, urea, potash, TSP) - physical mixtures of N,P,K. products and/or or mixtures of compound fertilizers particle with fixed NPK ratios ♦ Typically Bulk blen
Slide 12: Forms in which Sylvite is used
Forms in which Sylvite is used ♦ Granulated homogeneous mixtures each particle containing fixed NPK ratios – i.e. uniform distribution of nutrients in each – usually standard and fine grades ♦ Fluid Mixtures (solutions and suspensions) - A significant market. Can contain nitrogen, phosphorous, sulph
Slide 13: Why No Chloride Fertilizers – Chloride Sensitive Crops
Why No Chloride Fertilizers – Chloride Sensitive Crops* ♦ Many vegetable crops including cucumbers, onions, lettuce, early vegetables ♦ Potatoes – solid content (density) suppressed by Choride ♦ Most Fruits and especially soft fruits, stone fruits - decreased yield, leaf toxicity, necrotic burn ♦ Be
Slide 14: Why No Chloride Fertilizers – Chloride Sensitive Crops
Why No Chloride Fertilizers – Chloride Sensitive Crops1 ♦ High Sensitivity ♦ Avocdo, Legumes, Lettuce, Peach, Tobacco ♦ Mild Sensitivity ♦ Cotton, Oats, Potato, Soybean, Wheat , Grasses, Most fruit trees2 ♦ Low Sensitivity ♦ Barley, Corn, Spinach, Sugar Beet, Tomato 1Soil Fertility and Fertilizers,
Slide 15: Why No Chloride Fertilizers
Why No Chloride Fertilizers* ♦No Chloride Potassium fertilizer products: ♦From largest market size to smallest: ♦ Potassium Sulphate ♦ Potassium Magnesium Sulphate (Langbeinite) ♦ Potassium Nitrate ♦ Potassium Thiosulphate ♦ Potassium Polysulfide ♦ Potassium Carbonate ♦ Potassium Bicarbonate *Fertil
Slide 16: Potassium Sulphate - Production
Potassium Sulphate - Production ♦Potassium sulphate production is energy intensive and therefore expensive ♦ Decomposition of Kainite (Kieserite) followed by reaction with Potassium Chloride ♦ Reaction of Langbeinite with Potassium Chloride; Kainite with Potassium Chloride ♦ Mannheim process of reac
Slide 17: Potassium Sulphate – Market Size and Suppliers
Potassium Sulphate – Market Size and Suppliers ♦Market size estimated at least 5 million tons per year ♦90 % used as fertilizer (9 % animal feed; 2 % industrial) ♦Producers: ♦ Great Salt Lakes Mineral Co. - 500,000 tons; Evaporation Pond ♦ K + S Kali – 2 Million tons per year; Mined (Standard; Stand
Slide 18: Langbeinite Characteristics and Comparison to Polyhalite
Langbeinite K2SO42MgSO4 Non-Chloride Mineral Sulpahte Fertilizer - Characteristics of Langbeinite and Comparison to Polyhalite* ♦No chloride (Polyhalite also has no chloride) ♦Does not affect soil pH (Polyhalite may also be a neutral salt – requires investigation) ♦Can be blended with other fertiliz
Slide 19: Langbeinite Characteristics and Comparison to Polyhalite
Langbeinite K2SO42MgSO4 Non-Chloride Mineral Sulpahte Fertilizer - Characteristics of Langbeinite and Comparison to Polyhalite* ♦Low Salt Index (Polyhalite may have a low salt index – requires investigation.) ♦Naturally occurring mineral (Polyhalite is a natural occurring mineral) ♦Contains Potassiu
Slide 20: Langbeinite Characteristics and Comparison to Polyhalite
Langbeinite K2SO42MgSO4 Non-Chloride Mineral Sulpahte Fertilizer - Characteristics of Langbeinite and Comparison to Polyhalite* ♦Economical when two or three nutrients are required (Polyhalite should have same characteristics) ♦Very economic when three nutrients are required (Polyhalite should have
Slide 21: Langbeinite Characteristics and Comparison to Polyhalite
Langbeinite K2SO42MgSO4 Non-Chloride Mineral Sulpahte Fertilizer - Characteristics of Langbeinite and Comparison to Polyhalite* ♦Generally not used as a source for the total potash requirement. For most field crops will be recommended at a rate to supply most, if not all of magnesium and sulfur fert
Slide 22: Agricultural Research on Polyhalite
Agricultural Research on Polyhalite ♦ Polyhalite as a Potassium Fertilizer, K.A. Barbarick, Department of Agronomy, Colorado State University and Agricultural Experiment Station Project 15-2924; May 1989 ♦ Acid infertile soils typically benefit from the addition of K (Potassium), Ca (Calcium), Mg (M
Slide 23: Barbarick Paper – Abstract
Barbarick Paper – Abstract ♦ Sorghum-sudangrass (Sorghum bicolor, L. “NB280S) - Grain ♦ Greenhouse study ♦ Compare Polyhalite < 100 mesh to soluble fertilizer sources ♦ Treatment rates of 0, 100, 200, 300, 400, 500, 600 mg K/Kg soil (100 mg increments). ♦ Eight plant harvests and two soil samples (a
Slide 24: Study of Polyhalite – Ken Barbarick
Study of Polyhalite – Ken Barbarick ♦ Finely ground polyhalite produced larger total dry matter yields and total K uptake than the KsSO4 treatments ♦Increasing the K rate produced a positive quadratic dry matter yield largest at 400 mg K/kg soil and plant K uptake response and a negative quadratic C
Slide 25: Study of Polyhalite – Ken Barbarick
Study of Polyhalite – Ken Barbarick ♦ Soil extractable concentrations of Ca, Mg, SO4 and electrical conductivity of saturate soil pastes found at the end of the study were higher in the K2SO4 treatments indicating that the Polyhalite sources of these nutrients was less soluble ♦ A column leaching st
Slide 26: Barbarick Paper – Abstract
Barbarick Paper – Abstract ♦ Numerous earlier studies completed in Eastern Europe showed that Polyhalite was at least as effective as K2SO4 for potato (Solanum tubersom, L) and flax (Linum usitatissum, L) ♦ Panitkin (1967) concluded that Polyhalite was better than K2SO4 for potatoes and beets (Beta
Slide 27: Barbarick Paper – Abstract
Barbarick Paper – Abstract ♦ Mercick (1981) found that in spring barley experiments Polyhalite treated plants ourperformed those receiving K2SO4 over all solid fractions ♦ However a difficulty with these studies (current and prior slide) was that S, Ca, and Mg in non-Polyhalite treatments were not a
Slide 28: Barbarick Paper – Abstract
Barbarick Paper – Abstract ♦ Red Feather loamy sand soil; pH = 5.6; low in available K ♦ Polyhalite was 9.36% K, 13.24 % Ca, 3.66 % Mg, 0.06% Na, 20.8 % S, 0.06% Cl ♦ Comparison pots contained was equivalent separate minerals being composed of K2SO4, CaSO42H2O, MgSO47H2O, (NH4)2SO4 ♦ Control pots co
Slide 29: Leached Soils: Effect of Heavy Rainfalls on Native Potassium Status
Leached Soils: Effect of Heavy Rainfalls on Native Potassium Status and Pedogenic Leaching ♦ The native mineral nutrient status depends on parent material and subsequent weathering; the soils of Southern China, India, and Brazil are heavily leached. ♦ Soils formed under conditions of high annual rai
Slide 30: China: Highlights of the Workshop on Balanced Fertilization
China: From “Highlights of the workshop on Balanced Fertilization of Cash Crops in Tropical and Subtropical Regions of China” * ♦ Main outcome of 6th IPI Regional Workshop organized in cooperation with Institute of Soil Science, Academia Sinica, Nanjing as that there was a widespread deficiency of P
Slide 31: China: Highlights of the Workshop on Balanced Fertilization
China: From “Highlights of the workshop on Balanced Fertilization of Cash Crops in Tropical and Subtropical Regions of China” * ♦ Sugarcane study; Guangdong Province (36 % of China’s total cane production, early 1990’s) ♦ On Latosols high responses of sugarcane to K ♦ On Brown Limestone high respons
Slide 32: Leached Soils: Effect of Heavy Rainfalls on Mineral Nutrient Status
Leached Soils: Effect of Heavy Rainfalls on Native Mineral Nutrient Status and Pedogenic Leaching ♦ P, K, Mg, Ca essential nutrients are leached from the soil as they are replaced by hydrogen ions and aluminum ions ♦ Polyhalite should be of key significance in Southern China, India and Brazil as it
Slide 33: Leached Soils: Soil Potassium Supply - Inorganic Sources
Leached Soils: Soil Potassium Supply - Inorganic Sources* * Potassium nutrition in Australian high-yielding maize production systems, 5th Australian Maize Conference, Feb 18-20, 2003 33
Slide 34: Leached Soils: Cation Exchange (Native and Agricultural)
Leached Soils: Cation Exchange (Native and Agricultural)* ♦ Implications for leaching of nutrients including K ♦ Cation Exchange Capacity (CEC) is one of most important soil chemical property influencing K availability and retention in soil ♦ CEC is calculated in amount of negative charge per 100 gr
Slide 35: Leached Soils: Cation Exchange (Native and Agricultural)
Leached Soils: Cation Exchange (Native and Agricultural) * ♦CEC characteristics: Organic Soils > Clay and clay loams > silt loams > dark sands > light sands (Clay and organic matter have net negative charge) ♦ When Soil pH becomes less than 6 availability of nutrients such as phosphorus, potassium,
Slide 36: Leached Soils: Nutrient Mineral Leaching
Leached Soils: Nutrient Mineral Leaching * ♦ Higher CEC soils (greater than 10 meg/100g) experience little cation leaching ♦ On very low CEC soils (less than 5meg/20000g) some leaching of cations can occur. Fall applications of ammonium N and potassium on these soils could result in leaching below t
Slide 37: Leached Soils: CEC of Soils – Purdue Agronomy Guide
Leached Soils: Nutrient Mineral Leaching – CEC of Soils – Agronomy Guide, Purdue University www.ces.purdue.edu/extmedia/AY/AY-238.html Soil Group Example CEC in meg/100 kg Light Colored Plainfield; 3‐5 Sand Bloomfield Dark Colored Maumee; Gilford 10‐20 Sand Light Colored and Clermont‐Miami; 10‐20 Si
Slide 38: Leached Soils: Seasonal Agricultural Mineral Nutrient Leaching
Leached Soils: Effect of Heavy Rainfalls on Seasonal- Agricultural Mineral Nutrient Leaching ♦ This type of leaching refers to leaching of applied Potassium and refers to movement of Potassium beyond the plant root zone ♦ In most soils, potassium leach losses are small except in: ♦ coarse-textured o
Slide 39: Leached Soils: Seasonal Agricultural Mineral Nutrient Leaching
Leached Soils: Seasonal -Agricultural Mineral Nutrient Leaching ♦Soil acidity is produced if sulphate and phosphate fertilizer are delivered with ammonia as in ammonium sulphate or ammonium phosphate ♦Both chemical and organic nitrogen fertilizers may make the soil acid as the N is converted into ni
Slide 40: Leached Soils: Seasonal Agricultural Mineral Nutrient Leaching
Leached Soils: Seasonal -Agricultural Mineral Nutrient Leaching ♦ Timing, amount and intensity of rainfall is very important in determining Potassium leaching losses. An exemplification of this point can be found in the observations of Alison et. al. (1959) who reported that 23 % of the total potass
Slide 41: Potassium Status of Tropical and Subtropical Region Soils
Leached Soils: Seasonal -Agricultural Mineral Nutrient Leaching: Potassium Status of Tropical and Subtropical Region Soils * ♦ South America, Central America, Africa, Indian Subcontinent, Southeast Asia, Australia ♦ Aridosols – 33% (Virtually all in Africa) and Australia; not South America) ♦ Oxisol
Slide 42: Potassium Status of Tropical and Subtropical Region Soils
Leached Soils: Seasonal -Agricultural Mineral Nutrient Leaching: Potassium Status of Tropical and Subtropical Region Soils * ♦Aridosols – Non-Agricultural Land ♦ Oxisols – In tropical areas of South America and Africa ♦Most significant agricultural land; < 10 % weatherable material ♦ Low CEC – Low C
Slide 43: Potassium Status of Tropical and Subtropical Region Soils
Leached Soils: Seasonal -Agricultural Mineral Nutrient Leaching: Potassium Status of Tropical and Subtrpopical Region Soils * ♦ Considerably leached and leachable soils in these areas ♦ Chief causes in undisturbed and cropped lands is that weathered soils have low ability to hold potassium in fixed
Slide 44: Potassium Status of Tropical and Subtropical Region Soils
Leached Soils: Seasonal -Agricultural Mineral Nutrient Leaching: Potassium Status of Tropical and Subtrpopical Region Soils * ♦ Mountain Areas – 11% (Very highly weathered; quite acidic often with pH < 5) ♦ Ultisols – 9 % ♦ Entisols – 8% ♦ Inceptisols – 6 % ♦ Vertisols – 2% ♦ Mollisols – 1% * Potass
Slide 45: Potassium Status of Tropical and Subtropical Region Soils
Leached Soils: Seasonal -Agricultural Mineral Nutrient Leaching: Potassium Status of Tropical and Subtropical Region Soils * ♦ Availability of soil K thought to be lower in the soils of the tropics were kaolinite is the prevailing type of clay (Kaolinite is a 1:1 clay mineral sheet and has low CEC)
Slide 46: Potassium Status of Soils - Brazilian Cerrado
Leached Soils: Seasonal -Agricultural Mineral Nutrient Leaching: Potassium Status of Tropical and Subtropical Region Soils - Brazilian Cerrado* ♦ The Brazilian Cerrado occupies over 150 million hectares and represents considerable agricultural land ♦ Soil’s high level of acidity and low natural fert
Slide 47: Potassium Status of Soils - Brazilian Cerrado
Leached Soils: Seasonal -Agricultural Mineral Nutrient Leaching: Potassium Status of Tropical and Subtropical Region Soils - Brazilian Cerrado* ♦Kaolinite clays (1:1) predominate and these do not fix potassium ♦ In soils like those of Brazilian and Colombian savannas where kaolinite and iron and alu
Slide 48: Potassium Status of Soils - Brazilian Cerrado
Leached Soils: Seasonal -Agricultural Mineral Nutrient Leaching: Potassium Status of Tropical and Subtropical Region Soils - Brazilian Cerrado* ♦ According to Vilela & Ritchley less soluble K sources is an alternative for reducing Potassium leaching. ♦ The following order of Potassium retention has
Slide 49: Potassium Status of Soils - Brazilian Cerrado
Leached Soils: Seasonal -Agricultural Mineral Nutrient Leaching: Potassium Status of Tropical and Subtropical Region Soils - Brazilian Cerrado* ♦ Several coatings have been used to control rate of K release in soil and some were quite effective over an entire season ♦ K has been found to be more ret
Slide 50: Leached Soils - China: Organic and Inorganic Sources of Potassium
Leached Soils - China: Seasonal -Agricultural Mineral Nutrient Leaching: Organic and Inorganic Sources of Potassium in Intensive Cropping Systems* ♦ In the soils developed from shallow marine sediments and from the weathering products of basalt and limestone in southern PRC and in the soils derived
Slide 51: Leached Soils – China: Organic and Inorganic Sources of Potassium
Leached Soils – China: Seasonal -Agricultural Mineral Nutrient Leaching: Organic and Inorganic Sources of Potassium in Intensive Cropping Systems* ♦ Intensive cultivation of high-yielding crops in the major rice-producing area south of the Yangtze River has resulted in short supply of soil Potassium
Slide 52: Salinity (A significant Problem in India)
Salinity (A significant Problem in India) * ♦ Salinity causes osmotic stress which means that water availability is reduced by water obtained by either active transport or diffusion; salinity at 2000 ppm can be equivalent to a water reduction of 50 % (Managing Salinity in Citrus Fruits, B.J. Bowman
Slide 53: Salinity
Salinity * ♦ Salinity induced symptoms include reduced root growth, decreased flowering, smaller leaf size. ♦Chloride toxicity consists of burned necrotic or dry appearing edges on leaves ♦ As salinity increases orange trees will shed leaves and a thinning of the canopy becomes evident; this is foll
Slide 54: Salinity
Salinity * ♦ Approximately 20 % of cultivated soils are saline ♦ Soil salinity limits plant growth by ion imbalances causing extra energy consumption and sodium and chloride toxicity ♦ Potassium Sulphate and Potassium Magnesium Sulphate have lower salt indexes than sylvite and have been recommended
Slide 55: Salinity
Salinity * ♦ Selecting nutrient sources that have a relatively small osmotic effect in the soil solution can help reduce salt stress. The salt index of a material is a measure of the increase in soil solution osmotic effect when it is added to the soil. The salt index is specified to sodium nitrate
Slide 56: Salinity - Why Non-Chloride Potassium
Salinity - Why Non-Chloride Potassium ♦Low Salt Index – Important Where Soil Salinity is a Problem or for crops that require high K ♦ Potassium Chloride – 116.3 ♦ Ammonium Nitrate – 104.7 ♦ Sodium Nitrate – 100.0 ♦ Potassium Nitrate – 73.6 ♦ Ammonium Sulphate – 69.0 ♦ Potassium Sulphate – 46.1 ♦ Pot
Slide 57: Salinity
Salinity * ♦ Fertilizers, either applied dry or as a solution, influence the Total Dissolved Salts concentration in the soil solution. A fertilization program that uses frequent applications with relatively low concentrations of salts will normally result in less salinity stress than programs using
Slide 58: Salinity
Salinity * ♦ The salt index of natural organic fertilizers and slow-release products are low compared to the commonly used soluble fertilizers. However, high-analysis fertilizers may have a lower salt index per unit of plant nutrient than lower-analysis fertilizers since they may be made with a lowe
Slide 59: Polyhalite - Related Issues
Polyhalite - Related Issues ♦ Chlorides in certain cases can be of value through the suppression of plant diseases such as Take-all and common root rot.1 The use of KCl on potassium deficient soils can be considered in some case of value to suppress certain diseases, but must be on a trial and error
Slide 60: Appendices
Appendices Additional technical slides regarding soil chemistry and related follow this slide 60
Slide 61: Soil Potassium Supply Slide - Inorganic Sources
Soil Potassium Supply Slide - Inorganic Sources* (Appendix Slide) * Potassium nutrition in Australian high-yielding maize production systems, 5th Australian Maize Conference, Feb 18-20, 2003 61
Slide 62: Cation Exchange (Appendix Slide)
Cation Exchange (Appendix Slide) * ♦ Soil is composed 50 % of water and air and 50% of solid materials ♦ Solid portion is composed of Organic Material (OM) in various stages of decay and humification, and inorganic material ♦ Inorganic matter is composed of clay particles, silt, and sand ♦ Loam refe
Slide 63: Soil Potassium Supply - Potassium Movement
Soil Potassium Supply - Potassium Movement (Appendix Slide) * ♦ Root Interception: Exchange of ions through physical contact between the root and mineral surfaces ♦ Mass flow: Ions in soil solution are transported to the root with transpiration of water uptake by the plant, water evaporation at the
Slide 64: Soil Potassium Supply – Concentrations
Soil Potassium Supply – Concentrations (Appendix Slide)* ♦ Soluble Potassium – 0.1 % of total soil Potassium; does not form chelates or ion pairs; about 6 mg/L - Potassium fertilizer adds to this concentration; a form of exchangeable Potassium ♦ Less than 1/20 of Potassium requirements of crop is in
Slide 65: Soil Potassium Supply – Concentrations
Soil Potassium Supply – Concentrations (Appendix Slide) * ♦ Fixed Potassium (Non-Exchangeable) ♦ 1% to 10% of total Potassium – located at internal surfaces of 2:1 layer silicates (2 Si tetrahedral layers and 1 Al octahedral layer) ♦ in illite, vermiculite, smectite ♦ will be at equilibrium with sol
Slide 66: Soil Potassium Supply - Concentrations
Soil Potassium Supply - Concentrations (Appendix Slide) * ♦ Mineral Potassium - 90% to 98% of total Potassium locked in micas, feldspars, and illite (hydrous mica) ♦ Only released with weathering ♦ www.soils.wisc.edu/~barak/soilscience326/potassium.htm and Potassium in Agriculture, Robert D. Munson
Slide 67: Cation Exchange (Appendix Slide)
Cation Exchange (Appendix Slide) * ♦ Available K at the root level is from soluble K in water and K adsorbed to clay exchange sites ♦ During the growing season non-exchangeable K may become water soluble or exchangeable and become available to plants ♦ Non-exchangeable K is trapped in mineral lattic
Slide 68: Cation Exchange (Appendix Slide)
Cation Exchange (Appendix Slide) * ♦ Cation Exchange Capacity (CEC) is one of most important soil chemical property influencing K availability and retention in soil ♦ CEC is calculated in amount of negative charge per 100 grams of oven dried soil (meg/100 g) ♦ CEC characteristics: Organic Soils > Cl
Slide 69: Cation Exchange (Appendix Slide)
Cation Exchange (Appendix Slide) * ♦ Soil is composed 50 % of water and air and 50% of solid materials ♦ Solid portion is composed of Organic Material (OM) in various stages of decay and humification, and inorganic material ♦ Inorganic matter is composed of clay particles, silt, and sand ♦ Loam refe
Slide 70: Cation Exchange (Appendix Slide)
Cation Exchange (Appendix Slide) * ♦ Humus refers to organic material in soil which has reached a point of degradation stability ♦ Humus can be differentiated from organic matter in that the latter is rough looking material with coarse plant remains still visible which once fully humified it becomes
Slide 71: Cation Exchange (Appendix Slide)
Cation Exchange (Appendix Slide) * ♦Strength of cation adsorption influence availability: Al+3 > H+ > Ca+ > K+ = NH4+ > Na+ ♦ This series is known as lyotropic series ♦ The series explains why acid soils may be heavily leached in potassium and other positive ions such as Magnesium and Calcium * McLe
Slide 72: Cation Exchange (Appendix Slide)
Cation Exchange (Appendix Slide) * ♦Plant roots have CEC attributed mainly to carboxyl groups ♦Legumes and other plant species with high root CEC tend to absorb divalent cations preferentially over monovalent cations whereas the reverse occurs with grasses * McLean & Watson in Potassium in Agricultu
Slide 73: Cation Exchange (Appendix Slide)
Cation Exchange (Appendix Slide) * ♦CEC in meg/100 g Dry Root: Wheat - 23; Corn - 29; Bean – 54; Tomato – 62 ♦ Thus in grass-legume pastures (soybeans, alfalfa, and clovers) on soils containing low potassium, the grass survives but the legume disappears ♦ The legume roots excrete H+ and produce soil
Slide 74: Cation Exchange (Appendix Slide)
Cation Exchange (Appendix Slide) * ♦ The clay fraction of soil consists of aluminosilicate sheet minerals of Si tetrahedra and Al octahedra ♦The basic Si backbone is composed of (Si+4 (O-2)4)-4 sheets ♦ The basic Al backbone is composed of (Al+6 (OH-1)6)-3 * McLean & Watson in Potassium in Agricultu
Slide 75: Cation Exchange (Appendix Slide)
Cation Exchange (Appendix Slide) * ♦Clay minerals exist in: ♦ 1:1 sheets ( Alternating Si and Al sheets); e.g. Kaolinite ♦ 2:1 sheets ( Si sheet + Al sheet + Si sheet); e.g. Mica, Montmorillonite, and Vermiculite ♦ The major source of negative charge arises from replacement of Si+4 or Al+3 with cati
Slide 76: Cation Exchange (Appendix Slide)
Cation Exchange (Appendix Slide) * ♦ In mica substitution of Al+3 for Si+4 in the tetrahedral layer results in negative charge. ♦In montmorillonite Mg+2 or Fe+2 replaces the octahedral Al+3 producing negative charge. ♦ Isomorphic surface negative charges are not affected by pH ♦Another source of neg
Slide 77: Cation Exchange (Appendix Slide)
Cation Exchange (Appendix Slide) * ♦ CEC represents the total negative surface charge ♦ Only 5% to 10 % of negative charge on 2:1 clays are pH dependent ♦ 50 % or more of negative charges on 1:1 clays are pH dependent ♦ Soil OM charges result from carboxylic acid and phenolic acid groups * McLean &