Depths at Which Plants Absorb Water and Nutrients. 105 



favorable for growth by the use of too httle soil in small containers. In every 

 case the roots were better branched in the fertiUzed soil layers, and, correlating 

 with the growth of tops, the best root systems were found in containers 1, 2, 

 3,4, 9, and 10. Moreover, in general, greater amounts of water were also used 

 by these more vigorous plants, although the water-loss in any case is relatively 

 small, even when the 3 or 4 liters added to each container is taken into account. 

 The loss of nitrates at all levels is pronounced, the plants in container No. 9, 

 which were among the most vigorous of the lot, extracted rather large amounts 

 from the third foot of soil, thus indicating that the deeper portion of the root 

 system is very active in absorption. 



In order to determine the amount of nitrification or denitrification taking 

 place in the soil during the period of the experiment, analyses were made of 

 the soils in the control containers (Nos. 11 and 12) at all levels, both at the 

 beginning and at the end of the experiment. These data are given in table 38. 



Table 38. — Changes in nitrate-content in unfertilized soil. 



Table 38 shows that the soil at all depths was poor in nitrates when taken 

 from the field. Leguminous crops had not been grown on the area from which 

 the soil was secured for at least three seasons, during which period it had borne 

 Sudan grass and oats. In the unfertihzed soil layers where roots occurred 

 changes in the nitrate-content were small when compared with the large 

 amounts removed from the fertihzed layers (table 37). In the deeper layers, 

 where no roots occurred the increase or decrease in the nitrate-content is 

 proportionally small. Thus it may be seen that nitrification and denitrifica- 

 tion aifect the results given in table 37 to no great degree. 



Field Experiments, 1921. 



Early in the spring of 1921 an extensive series of experiments on the absorp- 

 tion of nitrates by several crops was begun. In addition to Manchuria barley, 

 Early Ohio potatoes {Solanum tuberosum), and Iowa Silver Mine corn {Zea 

 mays indentata), three native grasses were employed. These were wheat-grass 

 (Agropyrum glaucum), big bluestem (Andropogonfurcatus), and little bluestem 

 {A. scoparius). 



Large oak barrels 1.7 feet in minimum diameter and 2.8 feet deep were 

 used in part, especially for the earlier stages of growth, but these were supple- 



