Carbon/Nitrogen Ratios in Cacao Soils

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BY tabulating and comparing the results of a detailed laboratory examination of profile samples of cacao soils collected in January 1930, in the island of Tobago, British West Indies, one of us (G. G.) was able to demonstrate 1 a close correlation between the yielding capacity and the carbon/nitrogen ratio for the organic matter contained in the surface six-inch layer of soil. The mean ratio for ‘good’ soils yielding more than 8 bags (or 1320 Ib.) of fermented and dried cacao beans per 1000 trees (pickets) is 8.3 (21 samples), and for ‘bad’ soils yielding less than 8 bags per 1000, 6.8 (10 samples). Statistically, this correlation is highly significant (t=4.5), and the C/N ratio is not necessarily dependent on the total amount of organic matter present (t=1.1). Although a complete explanation of this relationship is not yet forthcoming, the result implies that the nature of the organic matter present, rather than its total amount, is the primary factor concerned in the productivity of cacao soils under the climatic, cultural, and soil conditions that obtain in Tobago.

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    Unpublished Thesis in part fulfilment of the requirements of the Associateship of the Imperial College of Tropical Agriculture, Trinidad. B.W.I., session 1929–30.

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HARDY, F., GRIFFITH, G. Carbon/Nitrogen Ratios in Cacao Soils. Nature 129, 132 (1932) doi:10.1038/129132a0

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