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The FAO Fisheries and Aquaculture Department's efforts in implementing the recommendations of the past session/s of the COFI Sub-Committee on Aquaculture

Sub-Committee on Aquaculture, Sixth Session, Cape Town, South Africa, 26-30 March 2012











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    Booklet
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    Standard operating procedure for soil nitrogen - Kjeldahl method 2021
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    This standard operating procedure (SOP) describes, in general terms, the quantification of the Kjeldahl nitrogen(KjN) content in soil samples. The advantages of this method are based on its robustness, low initial cost of the equipment and extensive application. However, there are disadvantages in using this method compared to others, for example, the use of potentially hazardous reagents that require consideration for safe operation are utilized, alongside the generation of hazardous waste and on-going cost of consumables, which can be mitigated via modified protocols that use lower quantities of reagents. Another limitation of this method is that it measures organic N and mineral N in the form of ammonium cation (NH4+), therefore, to measure the total N, the mineral N in the form of NO3- must be measured separately
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    Booklet
    Corporate general interest
    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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    Brochure, flyer, fact-sheet
    Brochure
    Standard operating procedure for soil available phosphorus - Olsen method 2021
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    This procedure is suitable for calcareous, alkaline, neutral, and slightly acidic soils containing CaPO4, since the calcium concentration in the solution is suppressed by the precipitation of CaCO3, increasing PO4 concentration in solution. Neutral and slightly acid soils (pH 6.0 to 7.0) may contain both Ca- and Al-phosphates. The NaHCO3 extractant can remove Ca-phosphates and phosphate adsorbed on the surface of calcium and magnesium carbonates along with Al-phosphates and is considered the most suitable extractant for these soils.