INJURIOUS EFFECT OF SULFATE OF AMMONIA. 127 



ous proportions of ferrous sulfate were added in one series, aluminium 

 sulfate was used in a second series and manganous sulfate in a third. 



The standard nutrient solution was prepared in two parts: (a) 20.5 

 gi-ams manganesium sulfate in 350 cubic centimeters of water; and (b) 40 

 grams calcium nitrate, 10 grams potassium nitrate, 20.56 grams disodium 

 phosphate in 350 cubic centimeters of w^ater. From each of the solutions 

 (a) and (b) were taken 100 cubic centimeters and added to 9,800 cubic 

 centimeters of water, together with a few drops of ferric chloride solution. 

 Tliis diluted nutrient solution was used in the culture bottles. 



SeedUngs of red clover were used in all these experiments with nutrient 

 solutions, because clover had sho^vTi the greatest susceptibility to the soil 

 influences on Field A. 



The experiments with sulfates of aluminium and iron have been fully- 

 described in Bulletin No. 161 of this station, and only a summary of the 

 results is given here. 



Effects of the aluminium and iron salts began to show by the end of the 

 first week, in stunted, tliickened roots, followed in a few days by a smaller 

 growth of leaves, when compared with seedhngs in the check nutrient 

 solutions. Cultures with 43 parts of aluminium in a million, or with 

 only 44 parts of iron, produced these effects, wliile in the higher concen- 

 trations employed the roots were killed.^ 



Calcium hydrate and calcium carbonate added to the bottles contain- 

 ing aluminium or iron neutraUzed their injurious effects in the lower con- 

 centrations, but were ineffective with high concentrations. Calcium sul- 

 fate w^as entirely ineffective as an antidote. 



The poisonous effects of the salts appeared to be exerted upon the tips 

 or growing parts of the roots. The rootlets died leaving a tliick, stubby 

 taproot. Microscopic examinations of the roots by Dr. G. H. Chapman 

 showed the cells in the growing parts to be either killed or arrested in 

 their development. 



Photographs of the clover seedlings which were published in Bulletin 

 No. 161 are reproduced here to show the characteristic effects of the 

 poisonous sulfates of aluminium and iron. 



Culture experiments in which manganous sulfate was added to the 

 nutrient solutions in graduated quantities were begun after it had been 

 demonstrated that ammonium sulfate fertilization was accompanied by 

 soluble manganese salts in the soils to which no lime had been added. 



A solution of manganous sulfate, MnS04.4 H2O, was prepared of Vio 

 molecular concentration, and measured amounts were made up to 250 

 cubic centimeters with the nutrient solution. Certain bottles received 

 fine calcium carbonate and others calcium suKate, so that the solutions in 

 those bottles were approximately saturated with the calcium salt. 



The scheme of the series is outlined below. 



1 In preparing this bulletin it has been noted that in Bui. No. 161, by an unfortunate error in 

 the decimal point, all figures relating to parts per million of iron in the nutrient solutions are only 

 one-tenth as large as they should be. This error caused iron to appear much more toxic than 

 aluminium, as compared in the tables of that bulletin. 



