212 EXPERIMENT STATION RECORD. [Vol.38 



rapidly in unbTOken soil cohimns than in pulverized soil. Aeration in a 

 column of soil uncultivated for seven years is far in excess of that required to 

 maintain aerobic conditions. 



" It has also been pointed out that such experimental data as are available, 

 regarding oxygen relations in normal field soils, indicate that obligate aerobic 

 conditions almost universally exist within the first foot of surface. There- 

 fore such beneficial effect as cultivating may have upon biological activity 

 can not be attributed to increased aeration." 



A comparative study of the nitrogen economy of certain Tennessee soils, 

 C. A. MooKus (Tennessee St a. Bui. 118 {1911), pp. 125-181, figs. 7).— This re- 

 ports the results of extensive pot experiments conducted during the 5-year 

 period of 1909 to 1914, inclusive, with four distinct soil types designated as 

 Coolceville, Crossville, Gallatin, and Jackson. The principal factors considered 

 were (1) the comparative utilization of nitrogen by crops on different soils 

 with regard to the nitrogen naturally present and that supplied by sodium 

 nitrate and farm manure; (2) the losses of soil and subsoil nitrogen under 

 different conditions, including cropped and uncropped, limed and unlimed, and 

 manured and unmanured soils; and (3) indications of nitrogen assimilation 

 from the air independent of legumes. Each soil type was removed in layers as 

 found in the field, transported to Knoxville and placed in 4-ft. cylinders sunk in 

 the ground, each cylinder inclosing a surface area of approximately rcrVus 

 acre. The cylinders v.'ere fully exposed to the weather, but protected from 

 birds by a screen cage. No artificial watering was given. Ten successive crops 

 were planted in each of 69 cylinders, the remaining 31 cylinders being kept bare. 

 Oats wei-e grown the first season, followed by wheat four seasons. Millet 

 followed each of the small-grain crops in the summer. The limestone and ma- 

 nurial treatments were moderate and well within the limits of farm practice. 

 Considerable tabulated data are presented and discussed from both the crop 

 and soil standpoint. The results are summarized as follows : 



" The largest crops were produced by the Gallatin soil, which had decidedly 

 the highest content of total nitrogen, but the yields decreased very rapidly in 

 the course of the five years. The second largest yields were obtained from the 

 Jackson soil, which had the lowest nitrogen content — only a little more than 

 one-third of that of the Gallatin soil. The Jackson soil, however, maintained 

 a more constant yield than any other, and in the last two years the crop 

 equaled those from the Gallatin soil. The Cookeville and Crossville soils 

 proved to be the least productive, and were practically on an equality In this 

 respect. For the Cookeville and Crossville soils constancy of yield was ob- 

 tained only on the limed cylinders. The results given by the 10 limed and 

 cropped cylinders of each of the four types were used, therefore, in deter- 

 mining the percentage of nitrogen recovery from manurial applications and 

 in certain other calculations. 



" The recovery by crops of the nitrogen applied in the form of sodium nitrate 

 vajied with the kind of soil as follows: Cookeville 45.38, Crossville 53.71, 

 Gallatin 87.08, and Jackson 72.21 per cent. The results are correlated with 

 the productiveness of the soils ; that is, the more productive the soil the greater 

 the root development to intercept the nitrate— -the greater the percentage of 

 nitrate nitrogen recovered. 



" The recovery by crops of nitrogen from the organic materials— manure and 

 manure plus straw — varied with the kind of soil as follows: Cookeville 29.82, 

 Crossville 34.52, Gallatin 37.58, and Jackson 23.88 per cent. The results are 

 correlated with the physical nature of the soils; that is, the more open and 

 porous soils show the highest recovery. 



