108 
soils have carried a mean of 2.29 inches, the difference being equivalent to 0.74 inch 
of rainfall. There is, therefore, comparatively Little indication that the differences 
in yield which have been secured are due to differences in the absolute amounts of 
soil moisture present in the different soil types upon which the crops are grown. 
The mean yields which have been secured under the different fertilizations adopted 
have been, using round numbers, for corn, 57 to 24 bushels per acre, making 33 
bushels in favor of the northern soils where nothing was added; 64 to 32 bushels, 
making 32 bushels in favor of the northern soils where 5 tons of manure were added 
per acre; j§9 to 38 bushels, making 31 bushels in favor of the northern soils where 10 
tons of manure were added; 09 to 45 bushels, making 24 bushels in favor of the 
northern soils where 15 tons of manure Mere added, and 04 to 31 bushels, making 33 
bushels in favor of the northern soils where 300 pounds of Acme guano were added. 
The mean yields of potatoes, in round numbers, have been 169 to 54 bushels per 
acre, making 115 bushels per acre in favor of the northern soils where nothing was 
added; 211 to 82 bushels, making 129 bushels in favor of the northern soils where 
5 tons of manure were added; 236 to 9(5 bushels, making 140 bushels in favor of the 
northern soils where 10 tons of manure were added; 254 to 97 bushels, making 157 
bushels in favor of the northern soils where 15 tons of manure were added; and 213 
to 79 bushels, making 134 bushels per acre in favor of the northern soils where 300 
pounds of Acme guano were added. 
With the southern soils 5, 10, and 15 tons of stable manure have increased the 
yields of corn at the rates of 7, 14, and 20 bushels per acre, while the yields of pota- 
toes have been increased at the rates of 28, 42, and 43 bushels per acre. With the 
northern soils 5, 10, and 15 tons of stable manure have increased the yields of corn 
at the rates of 7, 12, and 12 bushels per acre, and the yields of potatoes at the 
rates of 42, 67, and 85 bushels per acre. The larger increase of potatoes per acre as 
compared with the corn is apparent rather than real, on account of the fact that the 
corn is a much more concentrated product, containing much less water. If we com- 
pute the yields of shelled corn to the same per cent of water which the potatoes con- 
tain the increases in yield associated with 5, 10, and 15 tons of manure will stand, for 
the southern soils: 59, 116, and 169 bushels per acre — using a weight of 60 pounds 
per bushel instead of 56 — while for the northern soils the increase would be 59, 103, 
and 103 bushels per acre. 
It thus appears that the stable manure has produced an increase in yield of corn on 
the southern soils nearly proportional to the amounts of manure added, but the largest 
amount not being quite as effective, as indeed was to be anticipated. Relatively, on 
the northern soils the increase has not been so nearly proportional to the amounts of 
manure added, which again is as should be expected; first, because these soils carry 
more plant food in water soluble form than the southern soils do, and second, 
because the season this year has been less favorable to corn in the North than it has 
been in the South. Again, the manure has been relatively more effective on the 
northern soils in increasing the yield of potatoes than it has been on the southern 
soils, and this relation, in my judgment, is chiefly due to the fact that the climatic 
conditions have been more favorable for the potato crop in the North than they 
have been in the South, especially this year, which in the North has been unusually 
cool. 
There has been made a very critical and somewhat extensive comparison of the 
amounts of plant food which might be recovered by a single three-minute washing, 
in distilled water, of these soils, and it is found that as an average of 48 separate 
determinations of each of the surface 4 feet of the eight types of soil at the beginning 
of the growing season, in the middle of the growing season, and at its close, that in 
the aggregate for the 4 feet it was possible to recover by a single three-minute washing 
more than 207 pounds of potash per acre from the northern soils as against 138 pounds 
per acre from those of the South, making a difference of 69 pounds per acre more. in 
the soils which have given the largest crops. Of lime, expressed as Ca, there was 
washed out with the distilled water more than 795 pounds per acre from the northern 
soils as against 300 pounds from the soils of the South, making for this ingredient a 
difference of 495 pounds per acre more for the northern soils. In the case of 
magnesia, expressed as Mg, the amounts stand more than 273 pounds for the northern 
soils to L38 pounds for the southern. Of NO., the amounts are 2S5 pounds to 94 
pounds. Of HP0 4 the amounts stand 204 pounds for the northern to 111 pounds for 
the southern soils per acre. Of SO, there was recovered at the rate of 1,435 pounds 
per acre from the northern soils against 600 pounds per acre from those of the South. 
In addition to the potash, lime, magnesia, nitrates, phosphoric acid, and sulphuric 
acid, we have determined the bicnrbonatos, chlorides, and silica, and when the total 
water-soluble salts recoverable by a single three-minute washing in distilled water 
from the surface 4 feet of the two groups of soils are taken the amounts stand more 
than 3,846 pounds for the northern soils as against 1,635 pounds per acre for the 
