64 SOILS AND FERTILIZERS 



3. A large amount of partially decomposed organic matter. 

 Thus a muck soil may contain a greater weight of capillary 

 water than the weight of the dry soil itself. Farm manure 

 or green-manures are valuable for this purpose. 



4. A low soil temperature, if it is above the freezing point. 



5. A strong soil solution, such as is produced by proper 

 manuring and good tillage. 



6. The absence of oily material produced by decay of 

 organic matter. 



The conditions that are favorable to a large crop pro- 

 duction are, in general, helpful in increasing the capillary 

 water capacity of a soil. The effect of temperature, and of 

 oily material formed by decay of organic matter, are excep- 

 tions to this. Much may be done by tillage, drainage and 

 manuring to increase capillary water capacity. 



67. Movement of capillary water. — The movement of 

 capillary water is from particle to particle within the water 

 film, the film being continuous from one particle to the other. 

 The movement is always from the thicker part of the film 

 to the thinner part, because there is a tendency for the film 

 to assume the same thickness throughout. Capillary move- 

 ment may, therefore, be upward or downward or lateral. 

 Following a shower of rain the movement is downward, as 

 there is more moisture at the surface than below. Generally 

 the movement during the growing season is from the lower 

 soil towards the surface, because the roots and surface evapo- 

 ration continually remove water from the upper part of the 

 soil and this is replenished from the wetter soil below. The 

 lateral movement is usually slight. The factors that deter- 

 mine the rate of movement of capillary water are much the 

 same as those that influence its quantity. They are 

 (1) texture, (2) structure, (3) height of water column, and 

 to a less extent the other factors that influence the quantity 

 of capillary water. 



