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October 2017


By Conferences and Training No Comments

FERTASA will be hosting a Bio-Fertilizer workshop on 15 November 2017 at the CSIR International Convention Centre, Pretoria. Come and listen to guest speakers including Barbara Novak from Italy, Stephanie Roberts (Omnia) and Dr Rianto van Antwerpen (SASRI), Dr Robin Barnard (FERTASA) covering the following topics:  The International Scene Bio-Fertilizers vs Bio-Remedies South African Regulatory Framework Soil Health and Soil Condition Group 3 Fertilizer Applications The Way Forward FERTASA BIO-FERILIZER WORKSHOP – FINAL PROGRAMME  

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Langebaan Rock Phosphate - Langfos


By Phosphate products, Phosphorus & Phosphates, PLANT & SOIL NUTRITION No Comments

Langebaan Rock Phosphate (Langfos) is a phosphate rock (PR) of organic sedimentary origin that was widely marketed in South Africa until 1994. The original product Langfos Premium had a total phosphorus (P) concentration of 12.6% and citric P concentration of 3%, was milled and screened so that 80% of the particles passed through a 0.149mm sieve. The remainder of larger particles were used in combination with water soluble sources of superphosphate to manufacture granular NPK mixtures. In 2010 a new mine was opened and Langfos is once again available to farmers as an additional phosphate source for consideration. The total P content now ranges from 8 -10% and citric P concentration ranges from 1.8 -3.2%. 63% of the phosphate is in the tri calcium phosphate form and has a 20% calcium content as well as traces of Sulphur (S), Magnesium (Mg), Zinc (Zn), Boron (B), Copper (Cu), Molybdenum (Mo), Iron (Fe), Manganese (Mn) and Cobalt (Co). The product has a Group 2 Fertilizer registration in accordance with Act 36 of 1947. A comparison of Langfos Premium to the Langfos currently available:                                              Langfos Premium     Langfos                                              (Pre 1994)                      2010 – present Total P:                          12.6%                                8-10% Water soluble P:     0                                          0 Citric Soluble P:      3%                                      1.8-3.2% Particle size:             80% < 0.149mm          23% < 0.149mm 20% > 0.149mm           67% > 0.149mm  Langfos is not water soluble and should be considered to be a slow release fertilizer; approximately 50% of the P in Langfos becomes available for plant uptake in the first year of application, the balance over an extended period of time. From personal experience Langfos Premium has proven effective as a long term slow release source of P on acidic soils in Kwa Zulu Natal (KZN) and formed the basis of establishment of many Kikuyu pastures, sugarcane lands, avocado and citrus orchards where soil P test levels were found slowly increase despite limited or no application of superphosphate over periods spanning approximately 20 years. Thibaud et al. cite early researchers who found that the dissolution of PR is determined by gradients in the activities of phosphate, calcium, and hydrogen ions. The rate of PR decomposition is enhanced by soils with a low pH, high levels of reserve acidity and a low calcium status. PR was found to be more effective when applied to acid, well buffered soils than neutral soils and soils that had been recently limed. In addition to this soils with a large capacity to immobilize P from the soil solution generally promote more rapid and extensive dissolution of PR. Thibaud et al. (1992 & 1993) conducted research using a strongly P-fixing Balmoral clay and a weakly P-fixing Avalon sandy loam soil in greenhouse pot trails. They found that Langfos was not an effective substitute for superphosphate. It was however found that Langfos was more effective under strongly acidic conditions and that soils that retain P weakly may be more suited to fertilization with Langfos. The relative agronomic effectiveness (RAE) of Langfos compared to triple superphosphate however was 36% and 14%…

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Residual granular sulphur on the soil surface three years after application.

Sulphur or Sulphate?

By Sulphur Products No Comments

Sulphur (S) nutrition of crops has received a lot of attention since the advent of high grade phosphates and higher grade NPK fertilizer mixtures which typically contain very low levels of S. When considering your source of Sulphur (S) containing fertilizer, take time to assess the availability of the S sources that are available. Plants take up S in the Sulphate – SO42- form which is water soluble and immediately available for plant uptake while elemental S is not water soluble and must first be oxidized to the SO42- form by microbial action before becoming available for plant uptake. The oxidation rate of elemental S into the plant available SO42- form is also dependent on the particle size of the elemental S; the finer the particle size the quicker the conversion to the SO42- form. Granular elemental sources of S have been used in blends to “supply” the crops requirement, these granules don’t supply the crop’s immediate S requirement and can often be found encased in the soil or lying on the soil surface several years after application.

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Filler material



The South African fertilizer industry manufactures a broad range of NPK fertilizer products which are typically mixtures of two or more chemical compounds (raw materials) such as Limestone Ammonium Nitrate (LAN), Ammonium Sulphate, Mono Ammonium Phosphate (MAP), Potassium Chloride and Urea. All fertilizer products sold in South Africa must be registered in terms of the Fertilizers, Farm Feeds, Agricultural Remedies and Stock Remedies Act, 1947 (Act 36 of 1947) and are sold with a specific registered plant nutrient concentration which is printed on the fertiliser packaging. Not all of the constituents of the fertiliser raw materials used to manufacture NPK mixtures are plant nutrients (i.e. nitrogen (N), phosphorus (P) and potassium (K)). For example: LAN has a N content of 28%, the remaining 72% consists of hydrogen (H), oxygen (O) and approximately 21% limestone which acts as a carrier of the plant food. Ammonium Sulphate consists of 21% N, 24% sulphur and the remaining 55% consists of H and O. Potassium Chloride typically has a K content of 51% while the remaining 49% consists of chlorine. MAP consists of 11% N, and 22% P; the remaining 67% consists of H, O and carrier material. Urea consists of 46% N, the remaining 54% consists of C, H and O. All fertiliser products / raw materials are produced on large scale through industrial processes and are manufactured to the specification of their registrations in terms of Act 36 of 1947. Due to the nature of these processes it is normal that slight variances occur in the production process bringing about a slight variance in the concentration of plant nutrients in the different batches of product that are manufactured. The tolerance on concentration variance both upwards and downwards of a product is regulated by Act 36 of 1947. When raw materials are subsequently used to manufacture NPK mixtures, the variances in the plant nutrient content of the raw materials will have an impact on the final plant nutrient content of the NPK mixture. In order to ensure that NPK mixtures consistently meet specification, NPK mixtures are typically formulated to carry in the region of 1-2% filler material. All raw materials used in the production of NPK mixtures are analyzed on a continuous basis and where necessary the bill of materials for a specific product is adjusted to ensure that the final NPK product meets specification. In the event that one or more of the raw materials to be used has a plant nutrient concentration towards the lower end of the specification allowed for the raw material, the addition of filler will be reduced. Similarly, in the event that if the raw materials to be used have a plant nutrient concentration towards the upper end of the specification allowed for the raw material, the filler content may be increased. The filler material that is used in the production of mixtures is typically a course sand which is screened to ensure that 90% of the particle sizes range between 2.00 – 4.00 mm; it has…

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Save on lime costs and avoid subsoil acidity – use the right N source

By FERTILIZER PRODUCTS, LIME & LIMING PRODUCTS, Nitrogen, Nitrogen Products, PLANT & SOIL NUTRITION, Soil Acidity No Comments

Soil acidification is an unavoidable process that follows on from fertilization, different fertilizer products differ in their capacity to acidify the soil; substantial savings on lime costs can be made by selecting fertilizer products accordingly. Dr Erik Adriaanse explains how significant savings on lime costs may be achieved through the use of Limestone Ammonium Nitrate (LAN): Save on lime costs  

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