ANNUAL REPORT, 1929 331 



Fertilizer Distributors. (C. I. Gunness). A study of two types of 

 broadcast distributors indicates a great diiference in the uniformity of ap- 

 plication by the various machines. No results can be given at this time 

 as additional machines are to be tested, and all are to be tested with a 

 variety of materials. 



DEPARTMENT OF AGRONOMY 

 A. B. Beaumont in Charge 



Nitrogen Assimilation by Havana Tobacco. (A. B. Beaumont). Two 

 nitrate salts, four ammonium salts, ammonium nitrate, and fifteen organic 

 nitrogen compounds were used. In the selection of organic carriers pref- 

 erence was given those amino acids reported as constituents of cotton- 

 seed, since cottonseed meal is the principal carrier of nitrogen in Connecti- 

 cut Valley tobacco fertilizers. Cottonseed meal, itself, was used. Several 

 series of plants were grown in non-sterile and sterile water and sand 

 cultures. Analytical data on the chemical composition of the web of the 

 leaf were obtained for plants grown in non-sterile water cultures. (Analy- 

 ses were made by P. R. Nelson of the Chemistry Department.) 



Taking yield data, growth characteristics, and chemical composition 

 as criteria of assimilation, it is concluded that, of the various nitrogen 

 compounds studied, the nitrates are the most readily assimilated by 

 Havana tobacco, with urea, ammonium salts, asparagine and cystine next 

 in order of assimilation. Of the various amino acids of cottonseed meal, 

 only one, cystine, showed any appreciable assimilability; and cystine is 

 said to be present in cottonseed in small amounts only. Cottonseed meal 

 itself, or its hydrolyzed products, gave no evidence of being assimilated 

 in the unchanged form. Evidence points toward the need of ammonifica- 

 tion and nitrification of this organic nitrogen carrier before it can be 

 fully assimilated by Havana tobacco. 



Relation of the Form of Nitrogen to Root-rot of Havana Tobacco. (A. B 

 Beaumont). Ammonium salts and certain amino and amide compounds 

 have been found toxic to Havana tobacco in varying degrees. Browning 

 and rotting of the roots and dying and dropping of the lower leaves were 

 symptoms that accompanied this toxicity when the plants were grown in 

 unsterilized media and containers. Tobacco grown under sterile condi- 

 tions, but with the same forms of nitrogen, produced clean white roots. 

 This is taken as evidence that the symptoms mentioned are secondary 

 rather than primary effects of the form of nitrogen used. 



Plants grown in unsterilized solutions containing nitrogen as sodium or 

 calcium nitrate or urea produced healthy roots of a white or slightly 

 brownish white appearance. Mixtures of nitrates and ammonium salts were 

 toxic in proportion to the concentration of the latter. Nitrate nitrogen 

 tended to counteract the ill effect of ammonium nitrogen on tobacco. In 

 view of the data obtained, the toxicity of ammonium salts and certain or- 

 ganic compounds cannot be satisfactorily explained on the ground of 

 either physiological acidity or hydrogen-ion concentration. Rather, it 

 seems that improper metabolism caused by poor assimilation of nitrogen 

 offers the best explanation of all but the extreme cases of toxicity. 



