LYSIMETER, (from Gk.
a dissolving -I-- eietron, measure), or DRAIN -GA Uti E. A device for collecting and measuring the water (rain) percolating through soils. It is essentially a water-tight box or cylinder of definite content, as a cubic yard or meter, or inclosing a definite area, as or acre, to a given depth, sunk into the soil to a level with its top, and provided with a bott,,In so arranged that the percolating water may be drawn off and collected in a suitable reeeiNer for measurement and examination. In some eases the boxes are placed in pits dug to receive them and filled with (lie soil removed from the pits. Generally the purpose, however, is to maintain the conditions in the lysimeter as nearly like those in the natural soil outside as possible, and in this case the lysimeter box or cylinder is forced into the soil. and its bottom adjusted without disturbing the inclosed soil, or the box is built around an undisturbed block of soil. The most notable work with lysimeters has been done by Lawes. Gilbert. and Warington at Rothamsted. England; by Deli rainat Grignon. France: and in this country by Stockbridge at the Agrieul tural College, Amherst, Mass., and Sturtevant, liabcock, and Golf at the Agricultural Experi ment :station, Geneva, N. Y. The Rothamsted drain-gauges were constructed by digging a trench in the soil, gradually undermining the soil at the desired depth, and putting in perforated iron plates to support. the mass. The plates were kept in place by iron girders, the ends of the plates and the girders being supported by brick work. Trenches were then dug around the blocks of soil and these were inclosed in walls of brick laid in cement. A zinc funnel of the same area as the block of soil was fixed to the perforated iron bottom to collect the drainage water and conduct it into a suitable receptacle. The gauges were ILrubacre in area, and 94.40 and 60 inches deep in different cases. A lysimeter three feet deep and inclosing an area of acre, constructed by Stockbridge at Amherst, is shown in the figure.
Observations with the lysimeters at Rotham sted during twenty years showed that on the average slightly less than one-half of the rain fall escaped in the drainage of bare soils, the proportion varying slightly with the different depths. In observations made by Klucharo• at _Moscow, Russia, on hare soils inclosed in metal cylinders driven into the soil. approximately one fourth of the rainfall percolated through a depth of 20 cm, of soil. With soils covered with plants the percolation was much less. Stockbridge found that about one-fifth of the rainfall perco lated.through a bare drift soil three feet deep. Sturtevant concluded from observations made at Geneva that lysimeters as ordinarily constructed do not give results applicable to soils in their natural condition, mainly because the soil in the lysimeter is not in connection with a permanent water-table. Ile attempted to overcome this objection by a lysimetor provided with an artitieial water-table. With such a lysimeter the drainage was approximately 37 per cent. of the rainfall under sod, 41 per cent. with bare soil, and 43 per cent. with soil cultivated three inches deep. While it is doubtful whether lysimeters even with the greatest care in their construction and management give results repre senting accurately the conditions actually obtain ing in natural soils, they have proved valuable for comparative scientific studies, not only on percolation, but on the losses of soil constituents in drainage and on the process of nitrification (q.v.) in soils. For further information on the subject, consult: Gilbert, "Observations on Rain fall, Percolation, and Evaporation," in Rothum sled Memoirs, vol. vii. (London, 1890) ; Stock bridge. Inrestigations in Rainfall, Percolation, anal Eraporation (Boston, 1879) ; New York State Experiment Station Reports, 1882, 1887, 18S8, 1890; DebOrain, "Les eaux de drainage des terres in Annales Agronomiques, vol. xix. (Paris, 1893).