use up about 200 pounds of limestone. By the use of ammonium sulphate (NH4)2SO4) a small amount of sulphuric acid (H2SO4) is formed, as the plants use up the ammonia and leave the free sulphuric acid behind. Field experiments show that plats treated with ammonium sulphate become acid sooner than plats alongside treated with a similar amount of nitrogen in nitrate of soda or dried blood. When free sulphur is added to the soil, as in the dusting of plants for fungus diseases, it is soon oxidized to sulphuric acid and relatively large quantities of acid may be formed in this way.

It should be said in regard to organic acids that they may be largely oxidized, burned up, in the soil before they have exerted their effect. Also, if after combining with a base an insoluble compound is formed, as is often the case especially with compounds of calcium, this will gradually undergo oxidation leaving a basic ash to neutralize other acidity. In this way unleached manure has a tendency to reduce soil acidity; also the plowing under of green manures may finally help overcome acidity in surface soils as compared with land from which crops have all been removed.

It is not correct to say that acid soils are due to an accumulation of acids, such as described above, for hardly an appreciable amount of such acids are ever present in the free state in any soil. But the acids remove the bases from the soil, first the carbonates and then the basic constituents of the silicates; and when this process has gone on long enough the soil becomes deficient in basic materials. It is then potentially acid; that is, it behaves as an acid in contact with basic materials or a compound like limestone which readily parts with it basic constituents in the presence of even very weak acids.

FACILITIES FOR LYSIMETER AND OUT-DOOR POT CULTURE WORK AT THE STATION.*

J. F. BARKER,

DESCRIPTION OF LYSIMETERS.

A battery of twenty lysimeters was installed at this Station during the summer and fall of 1914. The diagrams and plates herein contained show the construction of this equipment without need of much detailed description.

The tanks are of 3/16-inch steel with riveted seams. They are four feet eight and one-half inches inside diameter, and 16 of them are four feet deep, 2 have a depth of eight feet and 2 a depth of two feet. Each has a conical bottom allowing in the center 6 inches additional depth. The surface area of soil exposed in each tank gives .0004 of an acre. Heavy coatings of pitch protect the tanks inside and out from rust and they are securely set in puddles of concrete. A two-inch bronze pipe passes from the bottom of each tank to the underground compartment or tunnel where the drainage water is collected.

The tunnel is made of reinforced concrete; there are glass lights in the roof similar to those for lighting cellars under city sidewalks. Double doors to the entrance of the tunnel at the bottom of the steps and doors again at the top of the steps make the compartment secure against freezing.

Drainage water is collected in receptacles made of common sheet iron and lined with "Bakelite," a synthetic compound of phenol and formaldehyde. This substance forms an insoluble and chemically resistant enamel lending itself admirably to the purpose. It is baked on in three successive coats each at a temperature of about 100° C. for one to three hours. The receptacles are about 11 inches in diameter and 23 feet in height and are made uniform in size so that the volume of water can be measured by running a graduated glass rod to the bottom. Three cans are provided for each tank, one to receive the overflow in times of emergency and one for aliquot samples. The drainage comes at very irregular intervals, corresponding to prolonged periods of excessive rainfall. In the summer the rapid evaporation of water from the growing crop and from the soil surface seldom permits of 4 feet of soil becoming saturated.

In filling the tanks attempt was made, of course, to place the soil in very much the same condition as found in the field. The soil was taken up in three layers, 0-8′′, 8-16′′, 16-36". The last depth formed the first two feet in the bottom of each 4-foot tank, the second depth occupied the next 12 inches in the tanks and the surface

8 inches from the field formed about the surface 9 inches in the tanks, they being filled to only about 3 inches of the top. Owing to the large amount of stone below 36 inches it seemed impracticable to take the soil to the full depth of 4 feet and yet get it from the places desired, and it is mainly of importance to have the soil in the different tanks uniform rather than to duplicate exactly the condition at some particular place in the field. Especial attention was given to mixing each layer of soil before it was placed in the tanks. Eight tanks were filled with a soil of the type common to the hill lands of southern New York, very deficient in lime and light in color, and in texture a loam containing a small amount of sandstone shale. The twelve remaining tanks received soil from the Station farm, calcareous in nature, of reddish brown color and in texture a loam. The latter soil is naturally adapted to alfalfa and clover while the first named type is just the opposite in this respect. The weight of soil for each 4-foot tank was 7170 pounds for the first type and 6850 pounds for the second. The greater weight of the first was due mainly to the presence of more stone. The total cost of constructing this plant, including a woven wire fence for protection, was not far from $2200.

PROBLEMS FOR STUDY.

The main problem for study of which the tanks were designed has to do with the nitrogen balance in the soil as affected by legumes such as clover and alfalfa on the one hand and by non-legumes such

such as grasses and small grain on the other. The problem is one which has interested Director Jordan for a number of years and which he expressed a desire to have studied. Other problems include: (1) The effect of depth of soil upon the supply of moisture or available plant food upon the amount and composition of drainage water; and (2) the rate of loss of fertilizing constituents from the soil in general and as effected by fertilizers applied, difference in character of soil and kind of crop grown. Opportunities will no doubt arise in the course of the work to obtain side lights on additional problems.

The only excuse, of course, for an elaborate construction of this type is to provide means for collecting the drainage water from definite amounts of soil, and problems to be taken up in this connection are only those which require an examination of the drainage water as an essential part of the study.

The main purpose of having the two distinctly different types of soil one naturally adapted to clovers and alfalfa, the other quite the opposite is to study their effects upon the accumulation of nitrogen in the soil. In order to grow legumes successfully on the poorer soil it was necessary to apply a certain amount of lime. All tanks receive a liberal ration of phosphorus and potassium, since for the purpose of this study none of the crops should be limited by a deficiency of those elements. Tanks 7 and 8 receive nitrogen as dried blood applied to the alfalfa crops in amounts equivalent to the alfalfa produced on 1 and 2.

The following is an outline of the cropping system on the basis of a 4-year rotation for each tank.