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periodical enrichment of these districts with fertilizing 
elements, under somewhat special conditions: direct enrich- 
ment with nitrogen from the air (nitrogen-fixing bacteria); 
enrichment with nitrogen, phosphoric acid, potash, lime and 
humus, by means of various complex substances, carried down 
by the river waters (manure from the flocks, drainage from the 
villages, &c.). The secret of making this country of real value 
lies in the close union of cattle-breeding with cultivation. 
DETERMINATION OF THE MANURIAL REQUIREMENTS CF 
SOILS IN THE BELGIAN CONGO. 
By F. SMEyvERs, 
Director, Colonial Office, Brussels. 
[ ABSTRACT. | 
The two following methods of investigation are used in the 
study of the soils of the Belgian Congo :— 
(1) Mechanical and chemical analysis. 
(2) Physiological analysis by plants, either by means of pot 
cultures or in field experiments. 
For mechanical and chemical analysis two laboratories have 
been established in the Colony; one of these was first situated 
at Eala (Equator), but was transferred to Zambi (Lower 
Congo) in 1913; the other was erected at Elisabethville 
(Katanga) in 1912. 
The work of these two laboratories is devoted exclusively 
to the study of soils. They both use the same methods of 
analysis (Wohltmann Method), so that comparable results are 
obtained. One hundred and twenty-seven analyses were made 
in these two laboratories in 1913. A number of chemical 
analyses of Congo soils were made also in Belgium in different 
Government laboratories. 
This work is completed by physiological analyses of the soils 
by means of plant cultures. The necessary appliances for this 
study will be available before long in the Belgian Congo. In 
the meantime Mr. Schreiber, General-Director of the Belgian 
Agricultural Department, has conducted at the Hasselt experi- 
mental station a series of physiological analyses on five samples 
of soils taken at Zambi (Lower Congo), and four samples taken 
at Ganda-Sundi (Mayumbe). The nine samples were sown 
with maize and oats in pots. 
This experiment is now in progress, and is intended to 
reveal, through the plant itself, the elements that should be 
added to the soils to increase their productivity. The method 
