358 THE PRINCIPLES OF SOIL MANAGEMENT 



with bases as does clay. (2) Drainage and aeration are 

 likely to be better, as are all those conditions that con- 

 duce to solubility of plant-food. For these reasons, a 

 sandy soil generally gives larger returns the first year 

 from the application of manures, but shows less effect 

 in subsequent years unless the treatment is repeated. 

 Clay soils are, for these reasons, more likely to involve 

 a wasteful use of fertilizers than are sandy soils, except 

 in respect to loss of nitrogen in drainage, in which the 

 sandy soil is more likely to be at fault, especially if there 

 is no crop on the land. 



228. Soil-moisture content. Soils in a humid region 

 -commonly suffer from an excess of water in the spring, 

 and a deficiency in the summer. Cereals and many other 

 crops require the largest quantity of water at the time 

 of heading and blossoming, and the largest production 

 of crop can be secured only where the supply is adequate 

 at that time. It is safe to say that in the great majority 

 of cases crops raised, even in the humid region, suffer 

 at some time from a deficient water-supply. On the other 

 hand, it is well known that crops, almost without excep- 

 tion, suffer either by lateness of planting, or by delayed 

 early growth from an excess of moisture in the spring. 



A control of the soil-moisture supply should, there- 

 fore, remove the excess of moisture in a time of large 

 rainfall, and conserve it in time of drought. 



There are three means that may be employed to 

 bring this about: (1) Drains, especially by means of tile. 



(2) Use of green manures or other organic matter. 



(3) Good tillage. (See page 190.) 



Viewed purely from the standpoint of soil fertility, 



