294 MASS. EXPERIMENT STATION BULLETIN 171. 



smaller roots than plots 6 and 7, but its crop yield was the maximum in 

 every year but the fifth, when its yield was exceeded by plot 7 with a 

 fraction of a pound. 



The weight of roots in the potash group of plots numbered 9, 10, 11 

 and 12 increased from 9 without potash to 11 with a medium application. 

 The ^-ield of stalks followed the same order each year. 



The nitrate of soda group included ten plots numbered 31 to 40, inclu- 

 sive. The weights of individual roots from any one plot varied consider- 

 ably from the average for that plot, but the plot averages showed fairly 

 consistent changes in size of roots with amount of nitrogen applied in the 

 top-dressing. The weights of roots from plots 31, 32 and 33 were, respec- 

 tively, smaller plot by plot than the weights of roots from plots 34, 35 and 

 36. The weights of crops did not follow the same order, but were in several 

 instances reversed. 



The application of nitrate of soda in the spring on plots 31, 34 and 37 

 resulted in much larger roots than the summer dressing apparently pro- 

 duced on 32, 35 and 38. On the other hand, the weights of crops from 

 the summer-dressed plots were in nearly all cases the larger. Plot 40 

 without nitrate yielded roots no lighter in weight than plot 39, which 

 received a maximum dressing of nitrate of soda, divided between spring 

 and summer. The yield of stalks was, however, much smaller on plot 40 

 than on 39. The small roots with large yields contained higher percent- 

 ages of nitrogen than the roots bearing smaller crops, so there was diffi- 

 culty in correlating roots with crops of stalks, since the variations in pro- 

 portions of root constituents were possible factors in influencing growth of 

 stalks. • 



For Table of Weights of Roots see p. 278, series of 1910. 



