Depths at Which Plants Absorb Water and Nutrients. 113 



complete. The losses of water and nitrates in the sealed layers are given in 

 table 42. 



Table 42. — Loss of water and nitrates, May 4 io Atigust 15. 



Absorption of water at the various depths is directly correlated with the 

 abundance of roots and the time the roots were present and active at the 

 several levels. The nitrate losses, while decreasing with depth as one would 

 anticipate, are sufficiently marked to show clearly that in studies of soil 

 fertiUty more than the surface soil must be taken into account. 



The native grasses were planted as blocks of sod approximately 8 inches 

 long, 5 inches wide, and 6 inches deep. These were secured from the field on 

 May 4, when the new growth, which was cut back, was about 3 inches high. 

 The containers in which they were placed were filled with lowland soil to 

 which nitrates had been added at depths of 1 to 2.5 feet, seals being inserted 

 in the fertilized soil at depths of 1 and 2 feet respectively. The surface foot 

 of soil consisted of the rich loam taken from the crop plats. No seal or sand 

 was used on the surface. Openings the size and shape of the surface of the 

 sods were cut in the roofs to permit the growth of the grasses from the entire 

 blocks. The first foot of soil was kept well watered and the grasses grew very 

 rapidly. By July 20 flowering stalks had begun to appear, and by August 15, 

 when they were examined finally, they had made an excellent growth. Agro- 

 pyrum glaucum was 2.5 feet tall, but had not headed out, while Andropogon 

 furcatus had flowering stalks 4 to 6.7 feet tall, some of which were beginning 

 to blossom (plate 13 b). Unfortunately, Andropogon scoparius, which had 

 also made an excellent early growth, became waterlogged and could not be used. 



Table 43. — Loss of water and nitrates, May 4 to August 15. 



