Analysis of organic fertilizers and soil conditioners : variation of results and comformity with specification
1996
Zainab Hamzah | Lau, C.H.
Numerous organic materials which are used as fertilisers or soil conditioners are commercially available in Malaysia. In this paper, 13 samples consisting of 11 organic fertilisers and 2 soil conditioners were investigated. Variation of analytical results were studied and compared with those specified by the manufacturers. The organic materials were analysed for moisture and ash content, major elements comprising N, P, K, Ca and Mg and minor elements consisting of Mn, Fe, Al, Pb, Cr, Zn, Cu and B. Other analysis were pH, water-soluble nutrients and C/N ratios. Most of the materials have high moisture content with values ranging from 3.8 - 62.2 %. Their ash content were high with some having values of 70.6, 72.3 and 67.0 % respectively. Different organic materials contain different amount of N, P2O5, K2O, CaO and MgO. NRSP and malameal had more than 20.0 % P2O5, while Libfeed had 22.9 % N. Kelawar had the highest K2O content of 39.8 % compared with the lowest value of 2.8 % of Alaska Fish. Among the minor elements in the fertilisers, only Fe and Al are present in significant quantity. Although Cu, Zn, B, Pb and Cr were detected, their content were generally found to be low with most in the 10 - 50 ug/g range, pH of most samples ranged between 3.8 and 8.8. Four samples have low C/N ratio of about 6.5, suggesting that they are high N containing products. Within each sample, results of replicate determination varied considerably. For P2O5, K2O, MgO and CaO, the coefficients of variation could be as high as 80 %. In many instances, agreement between laboratory analytical results and those specified by the manufacturers were poor despite repeat analysis of the sample. Formulation of standards is needed as seen from the variation of results obtained from the organic materials in this study.
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