398 



SOIL CONDITIONS AND PLANT GROWTH 



Energy relationships ; micro-organisms, 



denitrifying, 209. 

 --- nitrifying, 188. 

 --- nitrogen-fixing, 197, 199, 201. 

 --- other groups, 250 et seq. 

 ----- algae, 252. 

 ----- bacteria, 128, 176, 252. 



-- fungi, 252. 

 ----- protozoa, 252. 

 -- plants, 128. 



sources in soil, 93, 129. 



supply and soil population, 176, 21 r. 

 Engrais complementaires, 76. 

 Eremacausis, 23. 



Excretions from plants, possible toxic, 

 244 et seq. 



FACTORS affecting the growth of plants, 



30, 38- 



Faeces and nitrogen-fixation, 203. 

 Fallowing, effect on nitrates in soil, 



297 et seq. 

 --- soil, 15, 18, 297. 



harmful effect on fen soils, 310. 



losses during, 180. 



Farmyard manure as fertiliser, 19, 



236. 



-- effect on clover crop, 207. 

 -- increases moisture content of 



soil, 132. 



-- losses during storage, 193. 

 -- loss of nitrogen in soil, 181. 

 -- retained in surface soil, 152. 

 -- and solubility of phosphates, 



212. 



--- bacterial numbers, 269, 273, 



276. 



--- denitrification, 209. 

 Fatting fields in Romney Marsh, 317. 

 Fen, 134, 307, 308. 

 Fertility, transfer from new to old 



countries, 318. 



Field trials, necessity for, 19, 324. 

 Fine sand, composition of, 102. 

 -- effect in soil, 108. 

 -- properties of, 108. 

 silt, composition of, 102. 

 -- effect in soil, 107. 



properties of, 107. 

 llates in soil, 2 



Flagellates in soil, 291 et seq 

 Flocculation, absorption hypothesis, 

 161. 



electrical hypothesis, 161. 



of clay, 105, 160 et seq. 



silt, 160 et seq. 

 reversibility of, 161. 



Flooding, effect on soil, 325. 



Flora, plant, factors determining, 301. 



-- and soil reaction, 240. 



Fluorides and plant growth, harmful in 

 larger amounts, 76. 



necessary in small quanti- 

 ties, 56, 76. 



Folding, 306. 



Food supply and plant growth, 30, 



55- 

 effect of on water requirements 



of plants, 48. 



Forest soils, humus of, 136. 

 Fractions obtained during mechanical 



analysis, 98, 326. 

 Frost, late, 303. 



effect on soil bacteria, 279. 

 Fungi in soils, 137, 256 et seq., 282. 

 favoured by acid conditions, 



243. 



producers of humus, 177. 



Fulvic acid, 141. 



Fungoid pests, liability to, 53, 61, 70. 



GERMINATION, capacity of buried weed 



seeds, 85. 

 seed, 54. 



effect of salts on, 86. 



- CO 2 on, 85. 

 Glacial soils, 100. 



Glasshouse practice, effects of tempera- 

 ture, 46. 



watering, 46. 

 Glutamic acid as plant nutrient, 57. 

 Grain, composition of. See Seed. 



proportion to straw, factors affect- 



ing, 61. 

 increased by phosphates 



and silicates, 77. 

 Grass, growing, effect on fruit trees, 



246. 

 Gravel, composition of, 102. 



effect in soil, 109. 



properties of, 109. 

 Green manuring, 314. 



Gypsum, effect on plants, 74, 79, 86. 

 soils, counteracts alkalis, 74. 

 supply of potassium salts, 

 152. 



HEATED soil, changes in, 169, 281. 



Hochmoor, 134. 



Hoeing as manure (Tull), 5. 



Hormones, 87. 



Hot water treatment for forcing plants, 



88. 

 Humic acid, composition of, 138. 



fractionation, 140, 141. 



preparation and properties, 139. 



proof of acid nature, 143. 



protective effect on flocculation, 



162. 



