24 BULLETIN 1155, U. S. DEPARTMENT OF AGRICULTURE. 
EXPERIMENTS, 1917 TO 1919. 
The arrangement of the plats and the quantities of fertilizers 
applied per acre during the 3-year period from 1917 to 1919, inclusive, 
are shown in Figure 11. The three stages at which fertilizers were 
applied are designated as the A stage, when the plants were 3 inches 
high; B stage, when the first heads were emerging; and the C stage, two 
weeks after the first heads had emerged. 
The cost per ton of the fertilizers used each year and the average 
cost per ton for the three years (1917 to 1919) are shown in Table 
16. The cost of fertilizers per acre when applied according to the 
outline in Figure 11 was as shown in column 4 of Table 17. The 
yields obtained from the fertilizer experiments during the 3-year 
period from 1917 to 1919 are shown in Table 19. These are yields 
from single tenth-acre plats each year, except the check, which 
represents seven tenth-acre plats annually. 
In 1917 the fertilizer experiments were conducted on land that 
had produced four consecutive rice crops; in 1918, on land that had 
produced five consecutive rice crops; and in 1919 on land that 
had produced six successive rice crops. The land was fall-plowed 
each year except in 1918 and well prepared before seeding the 
following spring. 
The fertilizer experiments as conducted from 1917 to 1919 were 
for the purpose of determining the effect of applications of various 
fertilizers at different stages of growth on the yield and quality of 
the resulting crop. Obviously, it would be impractical to apply 
fertilizers in the field at any of the three stages of growth at which 
they were applied in this experiment, viz, when the rice was 3 inches 
high, when the heads were emerging, and two weeks after first 
heading. 
The fertilizers used, except nitrate of soda, acid phosphate, and 
sulphate of potash combined with acid phosphate, produced higher 
average }aelds when applied when the rice was 3 inches high than 
when applied at either of the later stages. The plat to which acid 
phosphate alone was applied when the heads were emerging produced 
exactly the same average yield as the one to which the phosphate 
was added when the plants were 3 inches high, while the plat to which 
both sulphate of potash and acid phosphate were applied two weeks 
after first heading averaged more than either of the two fertilized 
earlier. With this latter exception, all the plats to which fertilizer 
was added at first heading outyielded those to which it was added 
two weeks later. These results show quite clearly that the earlier 
the fertilizers are applied, the higher the average yields have been 
except when nitrate of soda was used. This fertilizer is very soluble 
and is likely to be carried away with the drainage water if applied 
early. 
The annual and average yields obtained from the plats to which 
fertilizers were added when the plants were 3 inches high are shown 
in Table 20, with the average annual gain or loss in pounds of rice 
and in dollars, as compared with the check plats. Only the actual 
cost of the fertilizers is taken into account, the freight from San 
Francisco, the cost of application, and the extra cost of handling the 
increased crop, if any, not being included. 
