178 MAGNESIA IMPRKGNATKl) SOILS. 



l''iom the above results of analyses it is seen that the 

 amount of magnesia in the soil g-reatly exceeds that of lime. 



The treatment usually recommended for soils containing 

 an excessive amount of magnesia is the application of lime, 

 but in this territoiy the cost of an adequate lime dressing, 

 excejjt in the neighbourhood of a lime deposit, renders this 

 method of treatinent prohibitive at the jjresent time. 



Artificial manures have been tried on several soils of the 

 D^'ke, the effects of which have been variable, and in many 

 cases very disappointing. 



The most effective and economical treatment for all tyjDcs 

 of soil on the Great Dyke which has yet been discovered has 

 been the application of liberal dressings of kraal manure — 

 a fact which it is interesting to compare with Davy's observa- 

 tion in 1814, when he stated that jjeat was a " proper and 

 efficient remedj^ " for the injurious effect of too liberal 

 dressings of magnesia lime. 



Regarding crops which have proved the most resistant 

 to an excess of magnesia, the following have thrived fairly 

 well on untreated suil : — Kaffir corn {Soighuiu vulgare), velvet 

 beans (Stijzolohiuin spp.), peinl millet (Pfiuiisetinii spicatuiu) 

 and ground-nuts (AracJiis hijpogaea). The amount (jf 

 magnesia which these crops will tolerate it is difficult to say, 

 but it is evident that t'^ey have produced a very fair yield) 

 where maize, wheat, lucerne, clover, mangolds and boer 

 manna have failed. 



So far as the investigative work in connection with the 

 soils of the Great Dyke has proceeded, my acknowledgments 

 are expressed to the past and present staff of the Chemical 

 Branch of the Rhodesian Agricultural Department — notably 

 Mr. A. G. Holborow, F.I.C., and Mr. E. V. Flack— for 

 valuable assistance in carrying out the analytical M'ork. The 

 most economical and practicable treatment of the Great Dyko 

 soils for pernunient agriculture is a problem which, unfor- 

 tunately, has had to be suspended during the period of the 

 Great War, and is one upon which much still remains to 

 be done. 



