WIIKAC SOILS t)F Till-: AI,l-:\.\ M )K I A l)I\ISI(»N. 11~ 



the propi^rtion of lime. i'liis, however, docs not seem lo applv 

 unless the al)sohite (|uantity of magnesia in the soil is large. 



In nn)st of these soils the amounts of magnesia present, 

 though douhtless adeciuate for crop re(|uiremcnts. are far from 

 h.igh, and certainly not sufficiently large — 'relative to the lime 

 present — to cause any injury to cereals. 



Some of the soils of the series, v\z., Nos. i. 2, 3 and 4, from 

 farms situated in the eastern part of the division, along the banks 

 of the Bushman's River, contain somewhat larger amounts of 

 magnesia — not only larger than those in the other soils of this 

 series, but also larger than the cptantities of lime in the soil. 

 There is. however, no ground for ascril)ing the crop deterioration 

 to this cause, for, even where they are higher in ])ro])ortion than 

 the lime. the quantities of magnesia seem still too small to do harm. 

 The whole question of injury to crops through abnormal lime- 

 magnesia ratios is still under investigation, and if there is any 

 doubt in respect of individual soils whether the quantity of 

 magnesia is nc^t too high relatively to the lime, the difficulty may 

 be easily settled by adding more lime to the soil. 



It is in caves along the Bushman's River bank that the 

 peculiar mineral, Bushmanite — a manganese magnesium alum — 

 occurs, covering the floors of the cave to a depth of several 

 inches. The roof of the cave contains magnesia, and it rests 

 on a bed of magnesium sulphate. The above analyses point in 

 the direction of these beds being attributable to the magnesia in 

 the soil of the adjacent farms. 



Taking in order the ten localities represented by the twenty 

 j>amples collected, general consideration of the results leads to 

 the following conclusions : — 



Nos. I and 2 are greyish-brown soils, botli containing a 

 satisfactory amount of lime and potash, the percentage of the 

 former being slightly lower in the cultivated than in the virgin 

 soil. The amomit of nitrogen in the virgin soil No. 2 is satis- 

 factory, but there is only a moderate proportion in No. i. Phos- 

 ]^hates are present in not more than fair amount in both soils. 

 There is much more magnesia in the virgin than in the cultivated 

 soil, seemingly due to extraction by the crops, a consideration 

 which shows conclusively that progressive deterioration of the 

 crops cannot be due to excess of magnesium in the soil, seeing 

 that the cultivated soil now contains less than when first put 

 under cultivation. The fertilisers most needed here are nitrogen 

 and phosphates. 



In colour, Nos. 3 and 4 are slightly more inclined to red than 

 the preceding two soils, to wdiich they are chemically decidedl}- 

 inferior. They do not contain more than fair amounts of any 

 of the mineral plant foods. This is the case not only with the 

 cultivated soil. No. 3, but also with the virgin soil, No. 4. The 

 cultivated soil, although poor in ])hosphatic material, contains 



B 



