INDEX 



433 



Nitrate production, effect of potas- 

 sium carbonate upon, 321 

 Nitric acid, amount brought to 



earth, Rothamsted, 20 

 decomposition by, 20 

 Nitrification, .317' 



increased by drainage, 225 

 loss of organic matter by, 152 

 temperature for, 21)8 

 Nitrogen, 393 



commercial forma of, ammonium 



sulphate, 399 

 calcium cyanamid, 400 

 organic substances, 400 

 sodium nitrate, 399 

 content of humus, 147 

 fixation, 317 

 furnished to crops by organic 



matter, 151 



in fertilizing materials, 405 

 in humus from different mate- 

 rials, 147 



lost by erosion, 3f>0 

 Non-tilled crops, factor in main- 

 taining organic matter. 171 

 Northwestern International Re- 

 gion, 105 

 Number of particles, 178 



Oats production, 1909, 414 



seed bed for, 349 

 Objects of a soil survey, 117 

 Oblique arrangement of particles, 



180 



Odor of soils, 177 



Optimum water content, defined, 212 

 Organic colloids, 132 



constituents of soils, chapter 



on, 142 

 matter, addition of, as sweet 



clover, 172 

 affecting capillarv movement, 



200-208 



hygroscopic moisture, 190 

 and fertility, loss of, in 



rotting of manure, 103 

 and nitrogen, lost by erosion. 



3fiO 



changes of, 145 

 comparison, chromic acid and 



combustion methods, 155 

 defined. 142 

 distribution of, in soil strata. 



147 

 effect of. on percolation, 218 



on shrinkage, 130. 135 

 in sweet clover, 173 

 28 



Organic matter increased by plowing 



under legumes, 172 

 increases moisture - holding 



capacity, 231 

 increasing amount of, aid in 



checking erosion, 303 

 in soils, amount of, depends 

 on altitude, 145 

 on latitude, 145 

 on limestone, 145 

 on moisture, 143 

 on vegetation, 144 

 kinds of, active, coal-like, 



inert, 142 

 loss on ignition compared 



with, 154 



losses of, by cropping, 151 

 by erosion. 151 

 by fallowing, 153 

 by fires, 152 

 by leaching, 152 

 by quicklime, 152 

 methods of estimation of. 153 

 chromic acid method. 154 

 combustion in oxygen, 



154 



loss on ignition. 154 

 maintaining, accumulations 



in pastures, 100 

 barnyard manures, 1(51 

 catch and cover crops, 



161 



green manures. 100 

 limestone, addition of, 



158 

 non-tilled crops, growing 



of, 171 

 organic residues, use of, 



170 

 phosphorus, application 



of. 15!) 



rotation of crops. 171 

 of soils, maintaining and in- 

 creasing, chapter on. 158 

 turning under and incorpo- 

 rating with soil, object of 

 tillage. 325 

 residues. 170 



substances lower surface ten- 

 sion. 205 



source of nitrogen. 400 

 Organisms, soil, chapter on, 31.1 

 beneficial. 317 



injurious, as plant diseases, 317 

 Origin of alkali. 278 

 of soil material, 1 



