Closeness of Plant Feediny. 101 



rapid rise, from nearly 300 Ibs. per acre in the surface foot 

 on the cultivated ground April 18, to about 500 Ibs. per 

 acre, but falling again on August ist to 250 Ibs. 



On the clover plots the start was at 250 ll>s. per acre in 

 the surface foot, rising to 290 Ibs. in 12 days. From this 

 date there was a slow decrease, falling to 220 Ibs. on the 

 date when the cultivated grounds were highest, at 600 Ibs. 

 per acre. 



116, Relation Between Nitrates and Total Soluble Salts ~ 



As a general rule when the nitric nitrogen in clay loams 

 is very high the total soluble salts, as indicated by the 

 electrical method, are very low. It will even happen that 

 the electrical resistance will show but little more salts than 

 are required to account for the nitrates, and this is perhaps 

 what should be expected for, if nitric acid is being formed 

 in the presence of carbonates, these would be decomposed 

 to form nitrates, and if the rate of nitrification were suf- 

 ficiently rapid, it might be that all the carbonates would be 

 decomposed and little else but nitrates left. 



The ratio of total soluble salts to nitrates in the surface 

 foot of the five cultivated fields represented by the curves 

 was a mean for the season of 2.14 to 1, while in the surface 

 foot of the clover fields it was 4.8 to 1. 



For the second, third and fourth feet the ratio is 7.29 to 

 1 for the corn and potatoes, and 9.97 to 1 for the clover, 

 alfalfa and oats; and these ratios are what would be ex- 

 pected if the formation of nitric acid destroys the carbon- 

 ates and bi-carbonates in the soil water. 



117. Closeness of Plant Feeding. It was pointed out in 

 (7) what small amounts of a fertilizer can be widely dis- 

 tributed through an acre of soil, and we may now consider 

 how extremely close plants do feed the nitrates of a soil. 

 In the table which follows are given the amounts of ni- 

 trates which were found in each foot of nine field plots, 

 represented by the curves, between July 1 8 and Sept. 1. 



7 



