the two forms of insoluble phosphate than from the reverted or
soluble forms.'

"The Indiana director reports as follows:

"'It will be seen that during the first and second years the rock
phosphate produced little effect, while the acid phosphate very
materially increased the yields. During the third and fourth
seasons, however, the rock produced very striking results, even
forging ahead of the acid. This and very similar investigations in
progress lead us to believe that rock phosphate is a cheap and
effective source of phosphorus where immediate returns are not
required.

"In the Ohio experiments eight tons of manure per acre were applied
once every three years in a three-year rotation of corn, wheat, and
clover, three different fields being used, so that every crop might
be grown every year. The average yields for the thirteen years where
manure alone was used were:

53.1 bushels of corn
20.6 bushels of wheat
1.63 tons of hay

"The average yields on the unfertilized land were:

32.2 bushels of corn
11.4 bushels of wheat
1.16 tons of hay