190-).] 



PUBLIC DOCUMENT— No. 3:5. 



121 



3 ; manure and fertilizers were a})plied on the 7th, and the 

 potatoes, which had been soaked in formalin solution for 

 prevention of scab, were planted on May 11. The crop was 

 thoroughly cared for throughout the season, although there 

 was some injury from bugs, apparently due to the fact that 

 the Paris green used for the first spraying on June 27 was 

 impure. The vines were sprayed three times with Bordeaux 

 mixture and Paris green : respectively, July 3, 18 and 30. 

 There was apparently little injury from blight. The leaves 

 on the plot to which manure was applied retained their green 

 color considerably longer than those on the other plots. On 

 September 10 they were estimated to he still about one-half 

 green, while the proportion still remaining green on other 

 plots was in general estimated to be about one-tenth to one- 

 eighth. By September 22 the tops were dead, and the pota- 

 toes were dug between that date and the 29th. The rates of 

 yield on the several plots and the source of nitrogen on each 

 are shown in the followino- table : — 



The yield on the different plots varies widely, that on the 

 plot receiving manure being the best in the field, and stand- 

 ing relatively much higher as compared with the plots re- 

 ceiving their nitrogen in the form of a fertilizer than in any 

 previous year. It is believed that this result must be in 

 large measure a consequence of the fact that the application 

 of barnyard manure tends to maintain the stock of humus 

 in the soil, and so keeps it in a condition more favorable to 

 productive capacity. Neither the soy bean nor the potato 

 leaves a residue which contributes materially to the humus 

 content of the soil, and no other crops have been grown 



