Plant Diseases in the Western Province. 527 



poorness of the soils, and their need of continuous all-round manuring. 

 The actual chemical analyses resulted as follows: — 



X(i. 1. N(i. 2. 



Moisture 30 .58 



Organic matter 1.01 1.03 



Nitrogen 014 .014 



Potash 033 .031 



Lime 034 .040 



Magnesium 016 .027 



Phosphoric oxide — 



Soluble in cold hydrochloric acid .029 .025 



Soluble in strong boiling acids . .060 .059 



" These figures abundantly confirm the inferences already drawn 

 from the results of the mechanical analyses, namely, that the soils 

 are very deficient alike in plant food and in humus-forming organic 

 substances, and low in water-retaining power. The proportion of 

 iron, too, is small, and, as in all soils composed almost exclusively 

 of silica, the inherent tendency of the soil is towards acidity, although 

 it seemed neutral to litmus. It is unlikely, however, that such low 

 acidity could produce the chlorotic symptoms mentioned. 



" The possibility of brak in the soil was also considered, and 

 analyses in that direction, resulting as below, were undertaken: — 



Xo. 1. Xo. 2. 



Calcium carbonate 048 .014 



i Calcium sulphate 022 Nil, 



Magnesium carbonate Nil. .004 



Magnesium sulphate Trace. Trace. 



Sodium sulphate 014 .034 



Sodium chloride 054 .053 



Total soluble salts (by analysis) 138 .105 



Total soluble salts (by weighing) — 



Before heating 192 .168 



After heating 120 



" The alkali salts may therefore be said to amount to from .06 to 

 .09 per cent, of sodium sulphate and chloride in the purface 18-inch 

 sandy layer, with the possibility of larger quantities being brought 

 up from greater depths by capillary attraction after irrigation, 

 assuming any brak salts to be concentrated in layers at lower levels 

 in the clay. Such an assumption would, however, scarcely seem to 

 be warranted in view of the natural slope of the ground and the state- 

 ment that it is well drained. 



" Taking the weight of an acre foot of soil at 4,000,000 lb., the 

 amount of alkali salts in a surface foot of the Wellington orchard 

 would be between 2400 and 3600 lb. per acre. This would correspond, 

 supposing the proportion of brak to be uniform all the way down, to 

 from 9600 to 14,400 lb. in the whole 4-foot layer, in which the amount 

 of sodium sulphate is from 560 to 1360 lb. and of sodium chloride 

 about 1650 lb. According to Hilgard, prunes were not affected by 

 9240 lb. of sodium sulphates, or by 1200 lb. of sodium chloride, oi' 

 by 11,800 lb. of total alkali. 



