218 EXPERIMENT STATION RECORD. [Vol.36 



Assimilation of fertilizing constituents of manure and fertilizers by crops. 



The average composition of 73 samples of moderately rotted yard manure used 

 in these experiments was phosphoric acid 0.35 per cent, potash 0.55 per cent, and 

 nitrogen 0.5 per cent. The author holds, contrary to B. Schulze's view, that the 

 fertilizing value of manure, as of commercial fertilizers, depends upon its per- 

 centage content of plant food (E. S. R., 26, p. 424). As with other fertilizers, 

 however, conditions of soil and season must be favorable for the best results. 

 Moreover, it appears that manure contains too little nitrogen to make it pos- 

 sible to secure the best use of the phosphoric acid and potash which it contains, 

 crops grown with manure alone being oversupplied with the latter. Therefore 

 the true value of the plant food of manure is not secured by its exclusive use. 

 In no case did manure alone give as high yields as manure with fertilizers, the 

 average relation of yields in all experiments being 1 : 1.3. Maximum crops, 

 especially of cereals, were often obtained with fertilizers alone, and in some 

 cases the results were higher than with fertilizers and manure combined. On 

 the other hand, in the case of hoed crops, such as potatoes and beets, better 

 results were uniformly obtained with fertilizer and manure combined. 



The ratios of grain to straw with the different treatments were as follows : 



Ratios of grain to straw with different fertilizer treatments. 



The percentage contents of phosphoric acid, potash, and nitrogen in the 

 crops grown in the experiments are given. These show that the composition 

 of the grain of cereals is quite constant, while that of straw and hoed crops 

 generally is very variable. The author concludes that such data can be 

 used only as a basis for further tests of the fertilizer requirements of plants. 



The results of these experiments indicate that if sodium nitrate is used 

 exclusively the amount applied must be increased from year to year, and, 

 furthermore, that the exclusive use of commercial fertilizers, as a rule, 

 accelerates the loss of nitrogen from the soil, while the use of manure with 

 fertilizers not only prevents loss but brings about a marked increase in the 

 nitrogen content of the soil. 



Summarizing the results of 37 rotations it is shown that of 100 parts of 

 phosphoric acid and of potash in the soil soluble in hydrochloric acid, 0.64 

 parts and 0.79 parts, respectively, were used by plants, and of 100 parts of 

 total nitrogen in the soil 1.09 parts were utilized by plants. 



