14 BULLETIN 1180, TJ. S. DEPARTMENT OF AGRICULTURE. 
duplicates are quite large. This is due to the fact that in nearly all 
instances duplicate plats were located at a considerable distance from 
each other and the soil variations were sufficient to account for the 
discrepancies. While these variations were large, nevertheless there 
was usually a gradual change in productivity from one portion of 
the field to another. 
AVAILABILITY STUDIES WITH RYE AND WHEAT. — SECTION I. 
This experiment was planned to give comparisons in yield between 
ammonium nitrate, sodium nitrate, ammonium sulphate, and cyan- 
amid at the rates of 10, 20, 40, and 80 pounds of nitrogen per acre. 
Half of the nitrogen was applied in the fall and the remainder as a 
spring top-dressing except in one series, where all the cyanamid was 
applied in the fall for the purpose of comparison with the other 
method of use. 
The differences in growth on the various plats were quite marked 
and also fairly uniform for the different sources of nitrogen at any 
given rate of application. Very early in April the growth on all plats 
was quite poor because of the late planting and very heavy rainfall 
both in the fall and spring. The soil on the entire area, and especially 
the ammonium-nitrate series, was not quite as well drained as is 
desirable. Soon after making the spring applications of nitrogen 
there was a very rapid growth which corresponded approximately to 
the total nitrogen supplied. The rye and wheat which received no 
nitrogen were the smallest and lightest in color, while that receiving 
the largest amount of nitrogen grew very rapidly and had a very 
dark green color. There was no appreciable difference between the 
different series of plats, except that where the spring application of 
cyanamid was made there was a slight retarding effect as compared 
with the other cyanamid series. 
The yields of grain and straw from the plats receiving the four 
different sources of nitrogen are given in Table 5. In considering the 
results for rye it will be noticed that usually the larger the amount 
applied up to the maximum application of 80 pounds of nitrogen per 
acre, the larger was the yield. With regard to the merits of the four 
sources of nitrogen, making allowance for soil variations, neither the 
growth nor yields indicated any marked differences. Ammonium 
nitrate produced larger yields than did the adjoining sodium-nitrate 
series, but the check plats were also better. The yields from the 
plats where all of the cyanamid was applied in the fall were the 
largest of any of the series and likewise showed the largest increases 
over the checks. The soil variations are too great to justify making 
sharp distinctions, but there is not the least doubt that cyanamid, 
when applied in the fall, produced results equally as good as any 
other fertilizer used. 
The wheat yields agreed very closely with those for rye and showed 
that under the conditions ammonium nitrate and cyanamid were as 
satisfactory sources of nitrogen as sodium nitrate and ammonium 
sulphate. The application of all of the cyanamid in the fall again 
gave slightly better results than the use of half in the fall and the 
remainder in the spring. 
