23 



BULLETIN OF 

 MASSACHUSETTS BOAED OF AGRICULTURE. 



ENGINEEBING. 



HINTS ON LAND DRAINAGE. 



All plants with which agriculturists and horticulturists concern 

 themselves are air plants, in that their roots are dependent upon 

 air in the soils in which they grow. Consequently the available 

 depth of any soil for agricultural purposes is practically limited to 

 the depth to which air can penetrate it, and cannot exceed, there- 

 fore, that part of it which is above the water table, or the level at 

 which water of saturation stands in the ground. 



Effects of Land Drainage. 



It is the primary object of artificial drainage, then, to increase 

 the effective depth of soils and to improve their general character 

 by lowering the water table in or under them. Among its benefits 

 and advantages are the following : — 



First. — It increases (with the aid of the deeper cultivation per- 

 mitted thereby) the amount of soil space and material for the 

 root-feeding of plants and for bacterial action and other agencies 

 in vegetable nutrition.* 



Second. — A greater proportion of the rain and snow water 

 leaches through and surrenders to a well-drained soil the elements 

 and agents of plant nutrition which such waters transfer from the 

 atmosphere to the soil, and, as a further consequence, the washing 

 away of the soil by the flow over its surface is reduced. 



* The degree of moisture has a marked influence upon the activity of the micro-organisms 

 of the soil which aid in the nutrition of plants, especially the root-tubercle bacteria and 

 bacteroids, through which leguminous plants, such as lupines, beans, clovers, alfalfa, etc., 

 assimilate or fix free nitrogen from the air. 



Experiments by E. Gain indicate that the development of such tubercles is about twenty 

 times greater in moist soil than in dry soil, with a corresponding increase in the assimilation 

 of free nitrogen. They also lead to the conclusion that a medium amount of moisture in the 

 Boil (fifty per cent of that required for complete saturation) is more favorable to the develop- 

 ment of root tubercles than higher or lower amounts. (United States Experiment Station 

 Record : Vol. V., pages 110-113; Vol. VI., page 870.) 



