12 
In considering the above data, it is necessary to allow for seasonal 
variations.' That is, while it is possible to obtain a good growth the 
whole year round, some months are more favorable for growth than 
others. Hence differences in the various crops may not necessarily 
be due to the action of the fertilizers alone. Nevertheless, the 
influence of the different fertilizers in the same series is comparative. 
The data show that this soil was very deficient in phosphoric acid, 
since in nearly every instance an increase in weight of the millet plant 
followed the addition of phosphate (see Pis. I and II). When phos- 
phoric acid was added at the rate of 0.007 per cent P 2 5 (I\/ 2 ), the 
soluble phosphates were the most effective. Phosphate rock was the 
least effective, while reverted phosphate, bone meal, and slag had an 
almost negligible influence. When phosphoric acid was added at 
the rate of 0.014 per cent P 2 5 (PJ, practically the same relation 
applied. By comparing the pots with and without legumes, where 
no phosphate was added, plant growth seems to have been benefited 
by the use of green manure. When added with the phosphates, the 
green manure did not show a very active influence except in the case 
of phosphate rock, when a better yield was obtained with the use of 
legumes. 
While an increase in growth of cowpeas was brought about by the 
use of phosphate fertilizer, there was no great regular variation due 
to the various phosphates. When applied at the rate of 0.007 per 
cent P 2 5 , the slags had the greatest influence. Applied at the rate 
of 0.014 per cent P 2 5 , sodium phosphate gave a higher yield than 
slags. The influence of acid phosphate, superphosphate, and phos- 
phate rock was quite marked. The highest yield in this series was 
obtained through the use of sodium phosphate at the rate of 0.021 
per cent P 2 5 . 
With buckwheat, as with the two previous crops, a marked influ- 
ence was exerted upon growth by all forms of phosphate. The rela- 
tive effect of the different fertilizers was quite similar, that is, while 
the soluble fertilizers were apparently the most effective, the differ- 
ence was very small. However, it may be safely said that 0.014 per 
cent P 2 5 was more effective than 0.007 per cent, while 0.021 per 
cent and 0.028 per cent were still more effective. 
The most important fact brought out in the second series of tests 
with millet was the marked increase in effectiveness shown by the 
phosphate rock and slags, which were about equal to the soluble phos- 
phates. In all cases 0.014 per cent P 2 5 produced a higher yield than 
0.007 per cent. Attentionis called to the fact that, when added at the 
rate of 0.007 per cent P 2 5 , the phosphate rock was the most effective. 
But when added in larger quantities, the soluble phosphates still 
maintain their superiority as regards effectiveness to such an extent 
that sodium phosphate added at the rate of 0.021 per cent P 2 5 
