180 NATURE AND PROPERTIES OF SOILS 



Two methods of procedure are available for the study of 

 drainage problems — the use of an efficient system of tile 

 drains, and the construction of lysimeters. For the first 

 method an area should be chosen where the tile drain receives 

 only the water from the area in question and where the drain- 

 age is efficient. A study of the amounts of flow throughout 

 a term of years will yield much valuable data concerning the 

 factors already discussed. An analysis of the drainage water 

 will throw light on the ordinary losses of plant nutrients from 

 a normal soil under a known cropping system. The advantage 

 of such a method of attack lies not only in the fact that a 

 large area of undisturbed soil is considered, but also in the 

 opportunity to study practical field treatments in relation to 

 the movement and composition of drainage water. 



The lysimeter method, however, has been the usual mode of 

 approaching such problems. In this method a small block of 

 soil is used, being entirely isolated by appropriate means from 

 the soil surrounding it. Effective and thorough drainage is 

 provided. The advantages of this method are that the varia- 

 tions in a large field are avoided, the work of carrying on the 

 study is not so great as in a large field, and the experiment 

 is more easily controlled. One of the best-known sets of lysi- 

 meters is that at the Rothamsted Experiment Station 1 in Eng- 

 land. Here blocks of soil one one-thousandth of an acre in 

 surface area were isolated by means of trenches and tunnels, 

 and, supported in the meantime by perforated iron plates, 

 were permanently separated from the surrounding soil by 

 masonry. The blocks of soil were twenty, forty, and sixty 

 inches in depth, respectively. Facilities for catching the drain- 

 age were provided under each lysimeter. The advantages of 

 such a method of construction lies in the fact that the struc- 

 tural condition of the soil is undisturbed and consequently the 

 data are immediately trustworthy. 



^awes, J. B., Gilbert, J. H., and Warington, E., On the Amount 

 and Composition of the Bain and Drainage Waters Collected at Bothar.i- 

 sted; Jour. Roy. Agr. Soc, Ser. II, Vol. 17, pp. 269-271, 1881. 



