244 Report on Crop PRopDvCTION. 
tilizer were applied per acre than where only 500 and 1000 Ibs. 
were used. 
Again, the question of the after effect of heavy fertilizing with 
purchased plant-food may well be introduced at this point. The 
experiments now considered furnish some evidence on this point. 
In 1901 no fertilizer was applied to Plats 6 to 10 of the Purdy 
field, crimson clover being turned under in the fall. An influence 
from fertilizers used in the three previous years is clearly indi- 
cated, as the yield from Plats 7 to 10 was considerably larger 
than on the check plat (No. 6) and nearly as large as on Plats 
2 to 5, which received the usual quantities of fertilizer. The atter 
effect of a chemical manure should be considered, therefore. 
Here we are again reminded that conditions other than the sup- 
ply of the compounds needed for growth limited the crop. 
The experiment on the Mars field should not pass unnoticed. 
The experiment was conducted in 1900 when a fairly large crop 
was secured, ranging from 188 to 199.8 bbls. of onions with the 
different quantities of fertilizer. The most noteworthy fact 
shown in this experiment is that the fertilizer, even in large 
quantities, failed to increase the crop. The average yield on the 
check plats was 193.7 bbls. and on the manured plats, 192.3 bbls. 
The comment of Mr. Sirrine, in immediate charge of the experi- 
ment, was that the owner of the land “‘ had used stable manure 
and fertilizers in such quantities during previous years that 
there was little need of fertilizer the present year.” Certainly 
an increase of available plant-food had no effect on the growth 
of the crop. It is suspected that this instance illustrates a mis- 
take in practice that is very frequently committed by farmers 
who follow intensive farming, viz.: the use of manure on soil 
already sufficiently charged with the available materials neces- 
sary to plant growth. 
