CONTENTS. 



PAGE. 



PART I. INTRODUCTORY . . . . . . . . . . . . . . . . 1 



Former theories of plant nutrition . . . . . . . . . . . . 1 



Available plant-food constituents . . . . . . . . . . . . 2 



Phosphate starvation and bone disease . . . . . . . . . . 3 



The origin of the investigations . . . . . . . . . . . . 4 



PART II. AGRICULTURAL CHEMICAL METHODS . . . . . . . . . . 5 



Divergent views on soil analysis . . . . . . . . . . . . 5 



Uniformity of method desirable .... 5 



Selection of samples ........ <> 



Preparation in the laboratory 



Chemical analysis, standard methods .... 7 



Extraction of inorganic plant-food 



Soil treatment with solvents . . . . . . . . . . . . . . 9 



Differentiation of plant-food constituents . . . . . . . . . . 9 



Choice of a solvent . . . . . . . . . . . . . . . . 12 



Extraction with standard Hydrochloric acid . . . . . . . . 13 



German Experiment Station method ...... 15 



Maeroker's method . . . . . . . . . . 15 



Hilgard's method . . . . . . . . . . . . . . . . . . 10 



Extraction with Citric acid . . . . . . . . . . . . . . 10 



Interpretation of results . . . . . . . . . . 17 



' Field operations . . . . . . . . . . . . . . 9 



Personnel and materiel . . . . . . . . . . . . . . . . 19 



Means of procuring samples . . . . . . . . . . . . 19 



PART III. RESULTS OF CHEMICAL ANALYSES . . . . . . . . 21 



Albany .. 23 



Albert 24 



Aliwal North . . 24 



Barkly West 25 



Beaufort West 28 



Bredasdorp 28 



Butterworth 32 



Caledon 33 



Cape 



Carnarvon . . . . . . . . .... . . . . . . . . 45 



Cathcart 46 



Ceres . . . . . . . . . . . . . . . . . . . . 50 



Clanwilliam . . . . . . . . . . . . . . . . . . 51 



Colesberg 52 



Elliot-Slang River . . . . . . . . . . . . . . . 53 



Fort Beaufort 54 



George . . . . . . . . . . . . . . . . . . . . 55 



Gordonia . . . . 60 



Graaff-Reinet 60 



