1899.] PUBLIC DOCUMENT — No. 33. 123 



Mixtures of muriate of })otash and sulphate of anuuonia 

 have proved in our experience in many cases objection- 

 able, on account of a nuitual decomposition into chloride 

 of ammonia and sulphate of potash. 



4. Observations with Dried Blood and Two Kinds 

 OF Leather Refuse as the Sources of Nitro- 

 gen FOR GROWING RvE IN PRESENCE OF AciD AND 



OF Alkaline Phosphates. 



In a preceding report an experiment has been briefly de- 

 scribed in which dried blood has been compared with leather 

 refuse as a nitrogen source for growing plants, when used in 

 connection with double phosphate and muriate of potash. 

 The differences of the crops raised were more marked with 

 reference to the yield of the straw than to that of the grain. 

 (For details, sec annual report of the Massachusetts State 

 Agricultural Experiment Station for 1894, pages 283-285.) 

 It seemed advisa])le to repeat the experiments, with such 

 modifications as experience suggested, to secure, if possible, 

 more decisive results, and to ascertain whether the degree of 

 availability of the nitrogen contained in the dried blood and 

 in the leather refuse would not be more strikingly modified 

 by using alkaline pJiospJiates instead of acid j)JtospJiates as 

 the phosphoric acid source. 



The following course was adopted. AVinter rye was again 

 selected for the observation. The soil used was taken from 

 the same locality, at eighteen inches below the surface, and 

 freed from coarse materials hy repeated screening through 

 a sand screen, as in the first experiment. The fertilizers 

 used were in each case carefully distributed throughout the 

 entire body of the soil. The boxes were the same which 

 had been used in the preceding experiments, containing 

 from seventy-five to eighty pouiuls of soil, having a depth 

 of eighteen inches. 



Six boxes were employed" in the experiment ; three served 

 for the trial with ai'id i)hosphate, — dissolved bone-black; 

 and three with an alkaline })hosphate, — phosphatic hlag 

 meal. The following mixtures of fertilizers were used 

 (weights are stated in grams ; thirty grams equal to one 

 ounce) : — 



