Depths at Which Plants Absorb Water and Nutrients. 101 



Thus the total nitrate-content at the beginning of the experiment was that 

 of the impregnation plus that already in the soil as it came from the field. 

 After the water-content of the soil had been determined, the amount of 

 NO3 used in fertilizing was calculated to the dry basis for each respective 

 level and these figures were used in the tabulations. 



The containers were placed a few inches apart on the cement floor, and 

 after soil from the fourth foot was tamped into the bottom 8 inches of each, 

 the usual wax seal was appUed. The soil from the third, second, and surface 

 foot was then placed in its relative position in each container in a similar 

 manner, the several layers being separated by wax seals. The containers 

 were filled in pairs, any two in a pair being exactly alike regarding the position 

 of the impregnated soil, etc., except that one was provided with apparatus for 

 aerating the soil at the four separate levels. This consisted of eight thick- 

 walled glass tubes about a centimeter in diameter also placed in pairs, one on 

 each side of the container, and of such length that they extended from the 

 surface where they were kept corked, well into the first, second, third, or 

 fourth foot of soil respectively. Thus by removing the corks and attaching 

 a large exhaust pump to one tube of the pair, moist air could readily be 

 drawn through the hermetically sealed layer of soil. All the even-numbered 

 containers were thus provided for aeration. 



The soil in containers 1 and 2 was impregnated with nitrates in the first 

 foot only; in 3 and 4 in the second foot; in 5 and 6 in the third foot; in 7 and 8 

 in the fourth foot; that in 9 and 10 was furnished with the salt at all levels, 

 while none was added to the soil in containers 11 and 12. 



Before adding the surface seal, two thin strips of wood, about 1.5 inches in 

 width, were placed edgewise across the containers and partially sunken in the 

 soil in such a manner that the seal was prevented from covering an area of 

 soil about 1.5 inches wide extending across the container. In this soil Man- 

 churia barley was planted thickly on November 4, after which it was covered 

 to a depth of about an inch with dry sand to retard water-loss from the 

 unsealed surface. The wax seal was then covered with 2 inches of sand and 

 the whole top of each container covered with white oilcloth provided with an 

 opening 1.5 inches in diameter to permit the exit of the plants. The covering 

 was added to exclude any water which might leak through the greenhouse 

 roof during storms or condense on the inner side and drip down. Finally, 

 an inclosure nearly 4 feet high was built around the containers and the whole 

 filled with sand. This insured a more uniform soil-temperature about the 

 developing roots, while barley grown in the sand about the containers, as well 

 as on the adjoining benches, helped to keep atmospheric conditions more 

 nearly comparable with those in the field. The general arrangement of the 

 containers, etc., as well as the development of the crop on December 23, is 

 shown in plate 9 d. 



The seed germinated well and the crop was so thick and developed so rapidly 

 that it was necessary to thin it by pulHng up some of the seedlings from time to 

 time during the first month after planting. Half of the containers were 

 aerated regularly at intervals of 10 to 14 days until the end of the experiment 

 on March 12, although at no time did the aerated plants as a group show a 

 more marked growth than the unaerated ones. However, the presence of 

 the nitrates had such a pronounced effect upon the growth and color of the 



