INJURIOUS EFFECT OF SULFATE OF AMMONIA. 125 



Table V. — Milligrams of Iron Oxide (FeJOz) and Manganese Oxide 

 (MnJJi) removed in Water from 100 Grams of Soil. 



[Soils representing Pennsylvania experiments with sulfate of ammonia.] 



The results of the chemical investigation of the effect of sulfate of am- 

 monia as a fertilizer in constant use on soils of four different experiment 

 fields show the accompaniment of soluble salts of either aluminium, iron 

 or manganese, or all three together, in the absence of a base hke hme. In 

 the presence of calcium carbonate, water has removed no observable 

 amounts of aluminium or manganese salts, and bare traces of iron salts, 

 indicating that Ume either reacts with the ammonium salt promptly, or 

 subsequently breaks up the salts of aluminium and manganese, and also- 

 iron salts, almost completely. 



Part II. — Water Cultures. 



Our investigation of the effects of sulfate of ammonia on the soils of 

 Field A included in its progress several series of water cultures in wluch 

 seedlings of rye, barley and clover were used to study the possibilities of 

 poisonous effects from the presence of soluble substances in the soils. In 

 the earliest series there were used water extracts made from soils of plots 1, 

 6, 7 and 8 for the purpose of learning whether the injurious effect of am- 

 monium sulfate applied to the soil would appear in the solution obtained 

 from the soil. 



The soil extracts were prepared in sufficient quantity by mixing soil 

 and water in the proportion of 1 part by weight of soil to 2 parts of water, 

 shaking frequently during a period of two hours, and then allowing the 

 hquid to clear by settling. The water extract was then carefuUy decanted 

 from the soil. A part of this extract was filtered through porcelain, under 

 pressure, to see whether the poisonous substances, if present in the extract, 

 were colloidal in their nature. 



Discs of paraffine, reinforced by wire gauze and punctured with numer- 

 ous holes, were arranged by means of suitable corks to float on a basin of 

 water flush with the surface. On these discs the seeds were moistened 

 sufficiently to germinate, and their radicles then penetrated through the 

 holes into the water below. The plan was essentially that described in 

 Bulletin No. 70, Bureau of Soils. 



As soon as the seedlings were large enough for the purpose, selected 

 ones were transferred to wide-mouthed bottles, which contained the soil 

 extracts. Each bottle contained 250 cubic centimeters, and 4 seedlings 



