"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
"If the corn is worth 35 cents a bushel, the wheat 70 cents, and the hay $6 a ton, in addition to the expense of harvesting and marketing, then the total value of the manure spread on the land is $2.07 a ton.
"Where $1.20 worth of raw phosphate (320 pounds) were added in connection with the manure the average yields were as follows:
61.4 bushels of corn 26.3 bushels of wheat 2.23 tons of hay
"And where $2.40 worth of acid phosphate (320 pounds) were used with the same amount and kind of manure the following average yields were secured: