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Use of phosphate rocks for sustainable agriculture










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    Book (stand-alone)
    Efficiency of soil and fertilizer phosphorus use
    Reconciling changing concepts of soil phosphorus behaviour with agronomic information
    2008
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    The efficient use of fertilizer phosphorus (P) is important for three main reasons. First, phosphate rock, from which P fertilizers are manufactured, is a finite, nonrenewable resource, and it must be used efficiently in order to maximize its life span. Second, there is a need to maintain and improve the P status of many soils for the growth of crops for food, fibre and bioenergy. This is particularly important in least-developed countries (LDCs) that need to increase food production a nd improve rural livelihoods. Third, the transfer of soil P (derived from fertilizers and organic manures) is a major cause of P-induced eutrophication in surface waters. This causes undesirable changes in their ecology, resulting in a decline in the provision of eco-services, often with serious economic consequences. This report reviews, analyses and synthesizes information on the efficient use of soil and fertilizer P. It presents information on the plant availability of soil and fertilizer P, with an emphasis on soil–plant interactions. The focus is on the changing concepts of the behaviour of both soil and fertilizer P and on the need to define and assess their recovery and, thus, P-use efficiency, more appropriately. The report also outlines strategies for improving P-use efficiency.
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    Booklet
    Standard operating procedure for soil available phosphorus - Bray I and Bray II method 2021
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    P-Bray 1 and P-Bray 2 methods are normally limited to acid soils with water pH values less than 6.8. The P-Bray 1 Method removes a fraction of the “adsorbed” phosphorus (Al-P, Fe-P, Mn-P and Ca-P but less efficient) while the P-Bray 2 Method is best suited to acid soils where rock phosphate has been the primary P fertilizer source and/or the major portion of P exists in the soil in various forms of calcium phosphate. Bray extractants should not be used on alkaline soils because the acid tends to be neutralized and/or excessive calcium phosphates may be extracted, giving a false high test for available P.
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    Meeting
    Phosphated Distarch Phosphate (Tentative)
    Residue Monograph prepared by the meeting of the Joint FAO/WHO Expert Committee on Food Additives (JECFA), 82nd meeting 2016
    2016
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    Prepared at the 82nd JECFA (2016) and published in FAO JECFA Monograph 19 (2016), superseding specifications for Oxidized starch included in the specifications for Modified starches prepared at the 79th JECFA (2014), published in FAO JECFA Monographs 16 (2014). An ADI “not specified” was established at the 26th JECFA (1982). Phosphated distarch phosphate is a modified starch. It is obtained by esterification/cross-linking of food starch with sodium trimetaphosphate or phosphorus oxychloride comb ined with esterification with ortho-phosphoric acid, or sodium or potassium ortho-phosphate, or sodium tripolyphosphate, in accordance with good manufacturing practice. The esterification results in partial substitution in the 2, 3- or 6- position of the anhydroglucose unit unless the 6-position is occupied for branching. In the case of cross-linking, where a polyfunctional substituting agent, such as phosphorus oxychloride, connects two chains, the structure can be represented by: Starch-O-R-O- Starch, where R = cross-linking group and Starch refers to the linear and/or branched structure.

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