400 



SOIL CONDITIONS AND PLANT GROWTH 



Marsh gas, oxidation of, in paddy soils, 

 213. 



Mathematical expressions, for plant 

 .growth, 31, 34, 42. 



search for, 27. 



value of, 28, 



Matiere noire (humus), 138. 



supposed index of fertility, 143. 



Maturation, 54. 



Mechanical analysis, defects of ordin- 

 ary, 95. 



difficulty of interpreting quantita- 

 tively, 170. 



fractions obtained during, 98. 



interpretation of, 326. 



methods, 353. 



not applicable to chalk or peat 



soils, 344. 



Odin's distribution curve, 95. 



Melanoids, 141. 



Mercury vapour lamp, effect on plant 

 growth, 88. 



Methods of investigation ; bacterio- 

 logical, 260. 



correlation, 104, 130. 



modern combined, 28. 



quantitative, 9. 



— statistical, 18, 29. 



Micro-organic population of soil, effect 

 on productiveness, 294. 



Micro-organisms in soil ; active and 

 resting stages, 216, 290. 



action of plant on, 296. 



agents causing decomposi- 

 tion, 175. 



— producing plant nutrients, 



general relationships, 252. 



groups of, 250 et seq. 



— methods of investigation, 257 



et seq. 

 relation to growing plants, 



129, 251, 252, 260, 294, 296. 



sources of energy for, 129. 



Mineral conslituents of plants, functions 

 of, 19. 



list of essential, 19. 



origin of, 9. 



— part of soil, 94 et seq., 351. 



— soils, 94. 



Mineralogical investigations ol soil, 100. 

 Minimum, law of, Liebig, 16, 28. 



Mitscherlich, 28. 



Mining (metals), injury to vegetation 



caused by, 85. 

 Mixed crops, 249. 



Moisture in soil, amounts of, 200. See 

 Water in soil. 



— equivalent of soil, 224. 



Molkenboden, 163. 

 Moorland soils, 307. 



bacterial activity in, 269, 307. 



Muck land, 310. 

 Mull, 136. 

 Mycorrhiza, 253. 

 Myxomycetes, 253. 



Nematodes, free living, 252. 



— parasitic, 253. 

 Niedermoor, 134. 



Nitrate immobiliser in soil, 179. 

 Nitrates, assimilation by micro-organ- 

 isms, 210 et seq. 

 algas, 256. 



— as plant food, 22. 



— contrast between production and 



destruction, 209. 



— effect on bacterial action, 199, 275. 



— essential plant food, 22. 



— formation in soil, 21. See also Nit- 



rification. 



— effect of growing plant on, 



297. 



of season, etc., 276. 



Nitrates and plant growth : 



effect of water supply, 40. 



qualitative relationships, 



57. 61. 



— — affected by potas- 



sium salts, 63. 



quantitative relationships, 



24, 40, 59, et seq. 

 (See also Saltpetre.) 



— in soil, alleged catalytic formation 



of, 216. 



amounts of, 145. 



decomposition of, 300. 



determination of, 348. 



— • maximum producible, 178. 



removal of, 178, 180, 235. 



seasonal fluctuations, 146. 



supply oxygen to organisms, 



209. 

 Nitre beds, 21. 



resemblance to fertile soil, 11. 



Nitrification, 187 et seq., 216, 



— an autocatalytic process, 188. 



— bacterial origin demonstrated, 23. 



— culture solutions, 188. 



— effect on soil phosphates, 191. 



— influence of organic matter, 190. 



— in sewage, more rapid than in soil, 



215. 



soil, limited by rate of ammonia 



production, 188. 



— not an oxidase action, 188. 



— organisms causing, 188, 191. 



— relation to soil fertility, 22. 



