Xll 



TABLE OF CONTENTS 



Sources of soil heat, 209 — Factors affecting soil tem- 

 perature, 210 — Specific heat, 211 — Variations of spe- 

 cific heat, 212 — Specific heat based on volume of soil, 

 213 — Effect of water on specific heat, 214 — Absorptive 

 power of soils for heat, 215 — Effect of color on absorp- 

 tion of heat, 216 — Effects of texture and structure on 

 heat absorption, 217 — Radiation of heat by soil, 218 — 

 Conductivity and convection of heat in soils, 219 — 

 Measurement of conductivity, 220 — Effect of texture 

 on conductivity of heat, 221 — Effects of humus and 

 structure on conductivity, 222 — Influence of moisture 

 on heat conductivity in soil, 223 — Effect of evaporation 

 of water on soil temperature, 224 — Effect of organic 

 decay on soil temperature, 225 — Relation of slope to 

 soil temperature, 220 — Heat supply and its effects, 227 

 — Control of soil temperature, 228. 



CHAPTER XV 



\J 



Availability of Plant Nutrients as Determined by 

 Chemical Analysis . . . . 



Solubility of the soil in various solvents, 229 — Com- 

 plete solution of the soil, 230 — Partial solution with 

 strong acids, 231 — Significance of a strong hydrochloric 

 acid analysis, 232 — Relation of texture to solubility, 

 233 — Nature of the subsoil, 234 — Calcium carbonate, 

 235 — Deficiency of ingredients and manurial needs, 236 

 — Partial solution with weak acids, 237 — Advantages 

 in the use of dilute acids, 238 — The one-per-cent citric 

 acid method, 239 — Usefulness of the citric acid method, 

 240 — Dilute mineral acids, 241 — Extraction with an 

 aqueous solution of carbon dioxide, 242 — Extraction 

 with pure water, 243 — Influence of absorption, 244 — 

 Other factors influencing extraction, 245 — The soil solu- 

 tion in situ, 246 — Devices for obtaining a soil solution, 

 247 — Composition and- concentration of the soil solu- 

 tion, 248 — Variability in composition and concentration 

 of the soil solution, 249 — Discussion of the theories 

 regarding soil solutions, 250. 



327-348 



