X CONTENTS 



PAGES 



oration, § 86; Mulches for moisture control, § 87; 

 The soil mulch, § 88 ; Frequency of stirring, § 89 ; 

 Depth of mulch, § 90 ; Effectiveness of mulches, 

 § 91 ; Other devices to prevent evaporation, § 92 ; 

 Rolling and subsurface packing, § 93 ; Removal of 

 water by drainage, § 94 ; Benefits of drainage, § 95 ; 

 Soil air, § 96 ; Soil tilth, § 97 ; Available water dur- 

 ing the growing season, § 98 ; Length of growing 

 season, § 99 ; Other results of drainage, § 100 ; Open 

 ditches, § 101 ; Tile drains, § 102 ; Arrangement of 

 drains, § 103 ; Digging ditches and laying tile, § 104. 



Questions on Chapter VI ....... 85 



Laboratory Exercises 85-89 



Determination of the percentage of water in a soil, 

 I ; Capillary movement in different soils, II ; Rate 

 of percolation of water through soils, III; Water- 

 holding capacity of soils, IV ; Moisture conservation 

 by means of a soil mulch, V ; Loss of water by tran- 

 spiration, VI ; Review problems Chapter IV and VI, 

 VII; Tile drainage, VIII. 



CHAPTER VII 



Plant-Food Materials in Soils . . . . 90-110 



Variations in content of plant nutrients in different 

 soils, § 105 ; The total supply of plant-food materials, 

 § 106; Upward movement of plant-food materials, 

 § 107 ; Plant nutrients compose a small part of the 

 soil, § 108; Relation of composition to productive- 

 ness, § 109 ; Available and unavailable plant-food 

 materials, § 110; Conditions that influence avail- 

 ability, § 111; Water-soluble matter in soil, § 112; 

 Relation of water-soluble matter to productiveness, 

 § 113; Chemical analysis of soil, § 114; Absorptive 

 properties of soils, § 115 ; Selective absorption, § 116 ; 

 The availability of absorbed fertilizers, § 117 ; Other 

 forms of available plant-food material in soils, § 118; 

 Loss of plant-food material in drainage water, § 119; 



