CONTENTS 



INTRODUCTION (pages 1-65) 

 GENERAL REMARKS ON THE IMPORTANCE OP WATER 



PAGES 



Definition of irrigation and drainage Importance of water 

 in crop production Plants adapted to intermittent 

 watering Variation in the capacity of soils for water 

 Adaptation of plants to soils of different water capacity 

 Variations in soils and in rainfall may make irrigation 

 or drainage needful Better aeration and deeper root 

 feeding in arid soils Explanations not entirely satis- 

 factory '. 1-9 



The Advantages of Abundant Supply of Soil Moisture. Large 

 volumes of water generally needed Part played by water 

 in crop production Relation to plant life Relation to 

 soil microbes Rains and irrigation may start formation 

 of nitrates by diluting soil moisture Relation of drain- 

 age to development of nitrates and soil fertility Soil 

 water dissolves ash ingredients of plant-food Water 

 causes oxygen, carbon dioxide and nitrogen to enter 

 the soil 9 15 



Water only One of the Necessary Plant-foods, Difference in 

 value of water for plant -food More water used than 

 any other substance 15, 16 



Amount of Water Used by Plants. Relation of climate to 

 water used Treatment of soil affects amount of water 

 used Irrigation and drainage modify amount of soil 

 moisture Apparatus used in measuring water used by 

 plants Aims of the experiments First trials with oats, 

 barley and maize Field results with maize Changes 

 of soil moisture in field Experiments with oats and 

 barley Experiments of 1893 to 1896 16-38 



(vii) 



