340 SOIL CONDITIONS AND PLANT GRO WTH 



Table XCIV. — Potash and Clay Contents of Various Soils. 



rainfall. Thin chalky soils, sandy soils, and soils rich in 

 organic matter are peculiarly responsive to potassic manures, 

 whilst clay soils generally are not. Carbohydrate-making 

 crops, like sugar-beet, mangolds, and potatoes also invariably 

 want more potash than they find in the soil or in dung. 

 Potassic manures also tend to prolong the life of the plant, 

 and, therefore, to increase the yield in dry districts where the 

 conditions all tend to early stoppage of growth. Illustrations 

 are afforded in Table XCV. where soils in dry districts, known 

 to respond profitably to potassic manures, are compared with 

 soils in places of much higher rainfall where potassic manures 

 do not prove profitable. 



Table XCV. — "Available" Potash in Soils of Known Behaviour 

 Towards Potassic Manures. 



