INJURIOUS EFFECT OF SULFATE OF AMMONIA. 123 



Since 1893 each plot had received acid phosphate and muriate of potash, 

 but plot 8 had not received any nitrogenous fertiUzer, while plot 24 had 

 been dressed with sulfate of ammonia at the rate of 220 pounds per acre 

 during each five-year period. One-half of each plot had received ground 

 Umestone annually at the rate of 2 tons per acre since 1908, wliile the other 

 half had received none during that period. 



The plots were seeded with clover at the time the soil samples were 

 taken in the faU of 1915. 



In a letter regarding the samples, Director Thorne said : — 



For several years there has been practically no clover on the unlimed ammonium 

 sulfate plots in our work. There are occasionally a few scattering plants, but 

 probably not 20 plants on the twentieth-acre plot. . . . When ammonium sulfate 

 is neutralized with lime we get a luxuriant growth. . . . There are usually at the 

 beginning of the season as many clover plants on the unlimed as on the limed 

 land, but they do not get much beyond the nutriment furnished by the seed, and 

 by harvest have disappeared. 



The soil of the Rhode Island experiment field is a sandy loam. The 

 samples for our use were taken from the permanent plots numbered 23, 

 25 and 29, wliicb have been repeatedly described in the annual reports of 

 the Rhode Island Agricultural Experiment Station. 



All tlii-ee plots have received acid phosphate and muriate of potash 

 smce 1893. Plots 23 and 25 have been supphed with nitrogen in sulfate 

 of ammonia, while plot 29 has had nitrate of soda. Plots 25 and 29 have 

 at irregular intervals received apphcations of lime, and in 1915 all three 

 plots received a dressing of it, but in different amounts. Plot 23 received 

 the equivalent of 500 pounds calcium oxide per acre, plot 25 received 1,500 

 pounds, and plot 29 received 1,000 pounds. This apphcation of 500 

 pounds per acre on plot 23 was the first in its history, and was made, as 

 Director Hartwell stated, ". . . because it was becoming so very unsuit- 

 able for crop growth." 



The soils were prepared for investigation by drying them at a moderate 

 temperature, and then sifting them through a coarse screen with seven 

 meshes to the linear inch, which is the same treatment that was used with 

 the soils from Field A. 



The samples from Rhode Island were used in percolation experiments 

 with quantities of 1 kilogram of soil and 1 liter of percolated water. 



The clay of the Ohio soils rendered this method impracticable because 

 the water percolated very slowly. The Ohio samples were accordingly 

 put in stoppered bottles, with twice as much water as there was soil by 

 weight, and shaken continuously for two hours in a machine. The solu- 

 tions were first filtered tlii'ough paper and finally through porcelain filters. 



Aluminium, iron and manganese were tested for, and when present in 

 measurable quantities their amounts Were determined. 



Aluminium could not be obtained in appreciable quantity from any 

 but the soil from plot 23 of the Rhode Island field. No manganese was 



