Potassium Research and Agricultural Production - The International ...

12. Sobulo, R.A.: Evaluation of analytical methods for determining Potassium status of Nigerian
soils. 10th Col1oquium InterlUltional Potash Institute. p. 119 (1973).
13. Tanaka. A.: Influence of specific ecological conditions on growth, metabolism, and potassium
nutrition of tropical crops (exemple: rice). 10th Colloquium International Potash Institute, p. 147
(1973).
14. Tinker, P. B. H.: Potassium uptake rates in tropical crops. 10th Colloquium International Potash
Institute, p. 169 (1973).
IS. Walker, P.: Problems of experimental design in tropical regions. 10th Colloquium International
Potash Institute, p. 359 (1973).
Statement concerning the paper presented by M. Drouineau
In agreement with the author the following statement of Mr. Mathjeu, Manager of
the FAO Fertilizer Programme, is given below as a supplementary information to
Mr. Droujneau's paper:
Mr. Mathjeu, FAO-Rome:
Mr. Droujlleau mentions that "in Africa in the past simple fertilizer trials with annual
crops did not show a clear response to potash, with the exception of certain crops and
leached soils'.
This opinion might appear pessimistic when considering the published results of
10605 fertilizer simple trials of the FAO Fertilizer Programme, dUling the last 10 years
in Africa.
These trials covered wheat, maize, groundnut, cotton, yame, rice, potato and leguminous
grain crops. All these trials particularly compare the physical results (yields)
and the economical ones (benefit) of a NP plot and a NPK plot. They are carried out
on the fields of small farmers by national extension services. The rates per ha to be
applied are discussed with the agronomic researchers.
The farmers-demonstrators are chosen amongst those farmers who already achieved
control over the other factors limiting production, as seed quality and crop protection.
We can say that the results of these trials represent the 'voice' of the soils of the small
farmers.
The following results were obtained: on all annual crops mentioned above, it is
highly probable that by applying all 3 nutrients NPK, the net benefit and the ratio
,
value of the additional yield
fertilizer cost
will be higher than with only an NP application.
For grain yields between 1000 and 2000 kg/ha the average fertilizer rates are 40-40-40
of N-P,05-K,o/ha.
] n contrast to the general potash response on other soils, forest soils are less responsive
due to their high potash content, resulting from preceding "burnings'. This potash
content will diminish, however, with succeeding crops.
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