18 BULLETIN 1180, U. S. DEPARTMENT OF AGRICULTURE. 
The growth and yields in the case of wheat showed no appreciable | 
difference between cyanamid with either of the two basic phosphates 
and ammonium sulphate with acid phosphate. The yields of wheat 
with sodium nitrate used in mixture with basic slag were also on a 
par with the cyanamid and ammonium-sulphate result^. With cal- 
cined phosphate and acid phosphate sodium nitrate gave smaller 
increases than any of the other mixtures. No significance should 
be attached to this, however, since these plats were located on 
poorer soil. Urephos gave very good growth, giving the best yield 
with basic slag of any of the mixtures and an average yield with 
acid phosphate. The large application of phosphorus may have 
partially accounted for the good results. 
The growth and yields of rye showed no appreciable difference 
between cyanamid, ammonium sulphate, and sodium nitrate with the 
different phosphate carriers except that some of the yields with sodium 
nitrate were low because of the poor soil on this portion of the field. 
This is shown by the wide variations in the yields of the two check 
plats. The yields of rye where fertilized with Urephos and basic 
slag were the lowest of any of the forms of nitrogen. The soil is 
decidedly poorer on this portion of the field, and doubtless this largely j 
accounts for the low yields. Urephos seemed to give as good responses | 
in growth as the other materials, but the fact that approximately 
30 per cent of the nitrogen is present as guanylurea sulphate leaves 
some doubt as to its value in general, since the latter compound is 
probably only very slowly avaSable for plant use. 
EXPERIMENTS OF 1920 AND 1921. 
The agricultural experiments reported above were continued at 
Muscle Shoals during the following two years. Modifications in 
the manner of using cyanamid were made, and the scope of the work 
was enlarged to include several additional nitrogen carriers. 
The methods of carrying out the experiments were essentially the 
same as those used previously except for variations in the fertilization. 
In order to make nitrogen the limiting factor all plats except those 
designated as "no fertilizer" received potassium and phosphorus. 
The rates of application used as a basis were 80 pounds of P 2 5 and 
40 pounds of K 2 for cotton and usually half these quantities for 
corn, but certain modifications had to be made where the nitrogen 
carriers contained either of these two elements. The sources of phos- 
phorus and potassium were acid phosphate and potassium sulphate 
unless otherwise noted. 
The experimental area included the 10 acres used previously, the 
yields from which have been given, and three additional fields of 
about 5 acres each, located near by. The layout of the plats, 
giving treatments for the season of 1921, are shown in the diagrams. 
(Figs. 1 to 4.) 
Field No. 1. 
The experimental work of 1919 on field No. 1 was continued during 
the following two years, using the same plat arrangements and so 
far as possible similar treatments for the same plats. The results 
are discussed under three headings corresponding to the three sec- 
tions of the field. A diagram of the field, showing the plat arrange- 
ments and treatments, is shown as Figure 1. 
