370 BOAKD OF AGRICULTURE. [Pub. Doc. 



DRAINAGE. 



BY PROF. WM. P. BROOKS, DIRECTOR OF MASSACHUSETTS AGRICULTURAL 

 EXPERIMENT STATION. 



There is a great field for the profitable investment of capital in the 

 drainage of land either at present entirely unproductive, or producing 

 far lower returns than it is capable of because of faulty conditions as 

 affecting the supply of water. It is not as generally recognized as it 

 should be that the returns in agriculture are controlled in a large 

 degree by the physical conditions in the soil, as affecting especially 

 the water supply and its temperature. Everybody knows that a field 

 where water stands during any part of the growing season needs 

 drainage, but it is not so generally understood that the productive 

 capacity of many other fields would be greatly increased by the es- 

 tablishment of better drainage conditions. It is essential for the 

 healthy growth of practically all the cultivated crops of the field, 

 garden and orchard, as well as for our most valuable grasses and 

 clovers, that the soil area occupied by the roots should contain air as 

 well as water. 



On going downwards in any field we reach a point below which 

 water occupies all the spaces between the soil particles. In this part 

 of the soil the water is relatively stagnant, and it is impossible for the 

 roots of most of our valuable plants to maintain themselves in that 

 portion of the soil thus filled with water. It is customary to designate 

 the water which thus stands between the soil particles as hydrostatic 

 water; and the surface of this body of hydrostatic water, the level of 

 which would be determined by sinking holes sufficiently deep to reach 

 it in various parts of the field, is usually designated the water table. 



Above the water table the existing condition is quite different. The 

 soil contains some air between its particles, while the particles them- 

 selves are surrounded by films of water which are held by capillary 

 attraction and surface tension. It is customary to designate the 

 water thus held on and between the particles of soil as capillary water. 



The capillary water of the soil may be derived in a considerable 

 measure from the rains and melting snows, a part of which is held as 

 the water sinks through the soil by the forces which have been re- 

 ferred to, but, especially in seasons of prolonged absence of rain, this 



