352 



INDEX 



Warp soils, 293 ; growth of potatoes 



on, 2 

 Water capacity of soil, 73 

 Water table, 84 

 Way on absorption of salts by soil, 



247 

 Weathering, 7, 9 ; due to alterna- 

 tions of temperature, 10 ; due to 

 frost, 1 1 ; due to water and car- 

 bonic acid, 13 ; due to roots, 14 ; 

 of granite, 19; of basalt, 22 

 Weight of a cubic foot of soil, 70 

 Wheat as an exhausting crop, 275 

 Wilfarth on fixation of nitrogen, 205 

 Wilting of plants in soils containing 



water, 94 

 Wind, transport of soil by, 10 

 Winogradsky on iron bacteria, 239 ; 

 on nitrification, 219 ; on nitrogen- 

 fixing bacteria, 212 



Woburn, lime in soil at, 240 ; 

 residues left by ammonium salts 

 at, 269 ; weight of cubic foot of 

 soil at, 64, 71 ; fruit farm, growth 

 of trees planted with grass, 123 



Wollny on composition of soil gases, 

 13 ; on effect of slope on tempera- 

 ture, 151 ; on oxidation of humic 

 acid, 198 ; on water required by 

 crops, 100 



Worms, fine soil brought to surface 

 by, 14 



Worn-out soils, 29, 298 



XEROPHYTES, 316, 321, 332 



Yeasts in the soil, 239 



Zeolites, 27, 44, 250 

 Zircon, 37 



PRINTED BY OLIVKR AND BOYD, EDINBURGH, SCOTLAND. 







