18 MASS. EXPERIMENT STATION BULLETIN 290 



The crops are estimated to have removed from each of the plots receiving 

 sodium nitrate, 228 pounds of nitrogen, while they had each received a total of 

 148.5 pounds of that element, or 79.5 poimds less than the crops removed. The 

 amount of nitrogen carried away from each of the plots that did not receive any 

 was 174 pounds, which is tlouble the deficit of nitrogen on the sodium nitrate 

 plots; therefore it appears that the latter plots received at least as much nitro- 

 gen as the crops could use. The crops on other forms of nitrogen fertilizers as a 

 whole did not remove as much nitrogen as those grown on sodium nitrate. 



The amounts of phosphoric acid and potash that were applied to these plots 

 were assumed to be more than enough to supply the crops that could be grown 

 with the nitrogen used. The amounts of these elements removed in the different 

 crops have been calculated in order to learn whether there was any shortage of 

 either at any time. 



It was found that the heaviest yield of hay in 1910 removed 13.5 pounds 

 potash and 3.7 pounds phosphoric acid; Japanese millet in 1913 carried away 

 19.3 pounds potash and 2.9 pounds phosphoric acid; clover in 1915 contained 

 20.5 pounds potash and 4 pounds phosphoric acid. 



The yearly application of chemicals contained 12.5 pounds potash and 8 

 pounds phosphoric acid for each plot. There is no doubt that the latter was 

 supplied in plenty. With regard to potash, the majority of harvests removed 

 much less than was applied; for example, the largest crop of oats contained 7.5 

 pounds potash, corn removed 9 pounds potash, four successive crops of hay, 

 1907, 1908, 1909, and 1910, removed 43 pounds potash and 50 pounds were ap- 

 plied. Since potash is not leached readily from the soil, as a rule there was a sur- 

 plus of it present for the occasional heavy demand. 



Measured by crop yields, manure was the superior source of nitrogen in seven 

 of the years and shared first place with ammonium sulfate in one. The crops were 

 hay, potatoes, soy beans, corn and Japanese millet. One condition affected these 

 crops in common. They were growing throughout the summer season and could 

 utilize the manure nitrogen as it became available. The hay crop may not usually 

 be regarded as a summer crop, but in this instance Brooks, in his report for 

 1899, stated: 



It is perhaps questionable whether much weight should be attached to the yields at the first 

 cutting, since full development was not reached on account of drought. The rowen gives a better 

 basis for comparison. 



Sodium nitrate was superior with eleven crops and shared with organic 

 nitrogen once. Its superiority was shown with all the different kinds of crops 

 except Japanese millet, and it may be regarded as the generally effk-ient nitro- 

 gen fertilizer. 



Ammonium sulfate was superior in seven harvests, while it shared superiority 

 once with organic nitrogen and once with manure. In five of these seasons, 

 lime had been recently applied. 



Organic nitrogen led the other forms in only three harvests, while it shared 

 the lead once with nitrate and once with ammonia. In four of these seasons the 

 rainfall was below normal; while in that in which it shared first place with am- 

 monium sulfate, a dry spring was followed by drenching summer rains, which 

 apparently washed all sodium nitrate down beyond the root level. 



Plots without nitrogen produced in 1911 larger yields of corn, both ears and 

 stover, than any of the plots with nitrogen fertilizers. The corn followed a crop 



