INDEX. 



ABSORPTION of substances by soil, 55, 58. 

 Acids, effect on plant growth, 47. 

 bacterial activity in soil, 125 



dilute, action on soil, no. 

 Air in soil, composition of, 107. 

 Alkali soils, 49, 112. 



Alkalis, supposed production by plants, 5. 



necessary for plant growth, 9 et seq. 

 Alumina in soil, 164. 



Ammonia, formation of in soil, 87. 



assimilation by micro-organisms, 101. 

 by plants, 31. 



Ammonifying power, 121. 



Ammonium salts and soil, reaction between, 



55- 



Artificial manures, 13. 

 Assimilation, effect of temperature on, 20. 

 Availability of organic manures, 84. 



BACTERIA the makers of plant food, 18, 102. 

 Bacterial activity and nitrate production, 126. 

 soil productiveness, 125. 



numbers in soils, 122, 12 }, 127. 

 Black soils, properties of, 143. 



CAESIUM salts and plant growth, 44. 

 Calcifuges, 142. 



Calcium carbonate, amount necessary in 

 soil, 163. 



effect in soil, 49, 63, 142. 



production in soil, 102, 136. 



rate of removal from soil, 64. 



salts and plant growth, 44. 

 in soil, 163. 



Carbon cycle in soil, 80. 



dioxide, effect of variations on plant 



growth, 22, 30. 



source of, for plants, 6, 10. 

 Carr, 71. 



Chalk soils, 142. 



Chlorides and plant growth, 46. 



Chlorophyll a magnesium compound, 45. 



Chlorosis, 49, 142. 



Clay, composition of, 54. 



properties of, 60. 



effect in soil, 61. 



soils, 144. 



Climate, a factor in determining soil type, 

 141. 



soil fertility, 159. 



Colloids, importance in soil, 58, 77, 112. 

 Composition of soil particles, 54. 

 Cooper-Hewitt mercufy lamp and plant 



growth, 51. 

 Copper salts are plant poisons, 48. 



DECOMPOSITION of organic matter in soil, 102, 



119. 



Denitrificatioa, TOO. 



Desert plants, osmotic pressure of sap, 28. 

 Disease organisms in soil, 118. 

 Dominant constituents of fertilisers, 13. 

 Drainage water, composition of, 66. 



EEL-worms in soil, 118. 

 Efficiency values of plant nutrients, 24, 36. 

 Electric discharge and plant growth, 50. 

 Energy relationships of plants, 19. 

 Enzymes as catalysts in plants, 19. 

 Eremacausis, 14. 



FALLOWING, effect on nitrates in soil, 138. 

 Farmyard manure as fertiliser, 39, 112. 

 Fatting fields in Romney Marsh, 149. 

 Fen, 71. 

 Fine silt, composition of, 54. 



properties of, 61. 



effect in soil, 145. 



Fluorides and plant growth, 46. 



Folding, 146. 



Food supply, effect of on water requirements 



of plants, 28, 35. 

 Fractions obtained during mechanical ana 



lysis, 54. 



GERMINATION, effect of salts on, 50. 

 Green manuring, 146. 



HORMONES, 50. 



Hot water treatment for forcing plant, 51. 



Humus. See Organic matter in soil. 



INJURIOUS factors, effect of, 23. 

 Inoculation of soil with bacteria, 100. 

 Iodides and plant growth, 46. 

 Iron salts and plant growth, 46, 49. 

 compounds in soil, 165. 

 Irrigation, 29. 



LEGUMINOUS crops, effect on soil, 85. 



nitrogen fixation, 97. 



Light and plant growth, 25. 



Lime as sterilising agent, 136. See also 



Calcium carbonate. 

 Limiting factors, 23. 

 Lithium salts and plant growth, 44. 

 Loams, 147. 



MAGNESIUM salts and plant growth, 45, 49. 



in soil, 56, 165. 



Manganese salts and plant growth, 46. 

 89 



