FIELD EXPERIMENTS WITH FERTILIZERS. I 27 



■ 6.25. This factor has been commonly used b}' chemists on the 

 assumption that protein substances in general contain prac- 

 tically 16 per cent, of nitrogen, although it is understood that 

 the percentage of nitrogen varies and that not all the nitrogen 

 present is in the form of true proteids. In these experiments 

 no attempt has been made to separate the true proteids from 

 the non-proteid compounds, nor has the possible presence of 

 nitrates been taken into account in estimating yields of protein. 

 The amount of non-proteid or non-albuminoid compounds is 

 usually quite small in crops of this class, and the chemical 

 methods in use for separating them from the true proteids are 

 not satisfactory. Tests for nitrates were made in connection 

 with the analyses of the crops from the field and pot experi- 

 ments in 1900, but only traces were found. It seems probable 

 that in field experiments where only moderate quantities of 

 nitrogenous fertilizers are used the presence of nitrates in the 

 crop may be safely left out of account. For these reasons, 

 and also because the use of the factor 6.25 is believed to be 

 sufficiently accurate for practical purpo.ses, protein has been 

 estimated in this way, in order that the results of these experi- 

 ments may be directly comparable with those reported in pre- 

 vious 5^ears, in which the same factor was employed. 



EXPERIMENTS WITH CORN. 



As shown in the diagram on page 124, corn is grown on the 

 two series of sections lettered A and F. The same kind of 

 corn, a Rhode Island white cap, is grown on both series of 

 sections. Seed is saved each year from each section for plant- 

 ing on the same section the following year. The original seed 

 planted on series F was obtained at the beginning of the ex- 

 periment in 1895, and that used on series A was obtained from 

 the .same farmer in 1898. 



Previous to 1898 both series of sections had been fertilized 

 alike. It had been observed, however, that the corn did not 

 seem to thrive as well on the plots supplied with sulphate of 

 ammonia, where the largest quantities were used, as on those 

 supplied with nitrate of soda, although the quantities of actual 

 nitrogen correspond in the two series of plots. It was thought 

 that the cause for the poorer growth on the sulphate plots 

 might be possibly a deleterious acidit}^ of the soil, resulting 



