Department of Soil Investigations. 53 



in these soils to show the effect of (i) nitrate fertilizers, (2) fer- 

 tilizers not containing- nitrogen, (3) farm manure, (4) lime, on the 

 soil extract when each of the crops mentioned is growing on the 

 soil. A space of twenty-five feet at the end of each plat is kept free 

 from any vegetation in order to ascertain the effect on the soil when 

 no crop is present to absorb nitrates. 



(b) Similar determinations are being made on corn land having 

 plats treated as follows: (i) cultivated, (2) mulched, (3) unculti- 

 vated but weeds removed by scraping, (4) weeds allowed to grow, 

 (5) fertilized. 



(c) The effect of complete and partial sterilization as described 

 under (i) and (2) on the soil extract, is being determined. 



(d) The production of plants and roots grown in the extracts of 

 the soils treated as already described. 



Tanks for soil investigation. — These tanks are now nearly completed. 

 They are intended to furnish receptacles for bodies of soil of sufificient 

 size to produce plants in a normal manner under approximately field 

 conditions, and yet afford opportunity for measuring a large number of 

 the factors affecting plant-growth. The construction is of concrete, 

 but the tanks will be lined. 



Each tank is four feet two inches square with a maximum vertical 

 depth of four feet six inches and a minimum, depth of four feet. There 

 are twenty-four tanks placed in two rows of twelve tanks each. Between 

 the rows of tanks is a tunnel the bottom of which is ten feet below the 

 top of the tanks. The tunnel is six feet wide. From the lowest point 

 in each tank is an outlet tube two inches in diameter and tin lined. It is 

 made large enough to permit of easy cleaning and has no bends in it. 

 A piston runs through the tube to within four inches of the upper end. 

 Between the perforated head of the piston and the soil, glass wool is to 

 be inserted. The piston can be withdrawn if it is desired to clean the 

 tube. Drainage water from each tank will be caught in a receptacle in 

 the tunnel. The lining in the tanks will prevent any soluble material in 

 the concrete from appearing in the drainage water. A constant water- 

 table at any desired depth may be maintained by raising the rubber tube 

 leading* from the outlet tube to a corresponding point below the surface 

 of the soil in the tank. 



The tanks as described will each contain between three and four tons 

 of soil, and the surface will constitute .0004 of an acre. They are built 

 with special reference to durability so that it will be possible to plan for 

 experiments to extend over a long period. The quantity of soil contained 

 is not too large to allow of accuracy in sampling and yet is sufficiently 



