120 MASS. EXPERIMENT STATION BULLETIN 176. 



sulfate of ammonia per acre; and plot 7 received no nitrogenous fertilizer. 

 In 1909, and again in 1913, hydrated lime was applied to one-half of Field 

 A, crosswise of the plots. The total amount in the two dressings was 

 9,000 pounds per acre. 



The ammonium sulfate solutions were used in the manner described in 

 Bulletin No. 165, viz.: 150 grams of air-dry soil were placed in a large 

 flask with 750 cubic centimeters solution and shaken frequently for two 

 hours. The solution was then filtered through paper, which gave a clear 

 filtrate with a yellowish tint. 



Manganese was determined by the colorimetric method described by 

 Schreiner and Failyer,! in which the manganese salts are oxidized to 

 permanganate by nitric acid and lead peroxide. 



The strengths of the solutions were tenth-normal (N/10) and normal 

 (N). The results obtained by the extracts from unUmed soils are tabu- 

 lated in Table I., together with the amounts of iron obtained from the 

 same soils in our previous work, and reported on page 81 of Bulletin 

 No. 165. 



Table I. — Milligrams Manganese Oxide {Mn-JD^ and Iron Oxide 

 (Fe.jOg) obtained from 100 Grams Air-dry Soil by Ammonium Sulfate 

 Solution. 



The stronger solution removed much more manganese than the weaker, 

 but not in proportion to its strength. The fertilization of plots 6 and 8 

 with ammonium sulfate evidently produced some manganese compounds 

 that were readily soluble in the solutions, since there was more manganese 

 obtained from those plots than from the other two. 



From the limed soils of these four plots there was removed no man- 

 ganese by N/10 or N solutions, but when stronger solutions of am- 

 moniiim sulfate were used (2^ N and 5 N), traces of manganese were 

 found in the soil extracts. This would appear to be due to the presence 

 of enough ammonium sulfate in the concentrated solutions to overcome 

 the lime and act upon the manganese in the soil. 



Since iron had been found by color tests to be generally present in water 

 extracts from the unlimed soils of Field A, while aluminium could rarely 



» Bui. No. 31, Bureau of Soils, U. S. Dept. Agr., 1906. 



