65 



All of the summer crops made a fair response to the 

 nitrogenous fertilizers during the years 1913-15. The 

 summer of 1916 was so extremely unfavorable that lit- 

 tle was made on any of the plots. 



During the late winter and early spring of 1916, it 

 was noticed that a brown crust had formed on the sur- 

 face of some of the highly fertilized plots, wdiich crust 

 contained an enormous amount of nitrates. Pot ex- 

 periments previously described indicated that this 

 brown crusted soil contained some material that was 

 toxic to plants. In order to get as much information as 

 possible on the cause of this toxicity, the plots were 

 carefully planted in 1917, both {he fallowed and the 

 cropped ends being planted. The spring was compara- 

 tively dry thus affording conditions favorable for salt 

 accumulation. 



At the end of the growing season all of the crops were 

 harvested and weighed green. The corn and sorghum 

 were cut near the ground, while the cotton and cow 

 peas were pulled, both root and top being weighed. 

 The vields obtained are set forth in Table XIV. 



Table XIV. — Yield of Crops from Plots Treated with 



Different Forms of Nitrogenous Fertilizers. 



Green Weight of Crops in Ponnds. 



^These sections of the sorghum plot received dried blood. 

 In 1913, only the first section was fertilized. The entire plot 

 was unfertilized in the fall of 1916. 



Considering the effect of the different forms of nitro- 

 gen, it will be seen that dried blood produced the poor- 

 est yields with each crop. The highest yield of corn 

 and peas was obtained from the plot treated with cot- 

 ton seed meal, while cotton 3'ielded best on the plot fer- 

 tilized with calcium cyanamid. The brown surface 

 crust before mentioned has never been noted on the un- 

 fertilized plot, nor on the plots treated with calcium 

 cyanamid. The nitrate content of these plots is usual- 

 ly much lower than that of the plots receiving cotton 

 seed meal or dried blood. Of the crops fertilized with 

 cotton seed meal, cotton w^as the only one that was 



