Transpiration as a Factor in Crop Production. 153 
DISCUSSION OF RESULTS. 
The results of the experiments during 1911 and 1914 have 
been summarized in Tables 63 and 64. The reader is referred 
to these two summary tables for a full and concise statement of 
results. The average production for the two years shows that 
three very distinct degrees of natural fertility existed. 
Without fertilizer, the average yields of dry matter from the 
infertile, intermediate, and fertile soils were 128, 257, and 344 
grams per plant, while the ear weights were 54, 121, and 
181 grams per plant. The respective amounts of water transpired 
per plant were 57.76, 91.87, and 107.51 kilograms. The water 
transpired per gram dry weight of ear was 1,223, 861, and 634 
grams according to fertility, while the water requirements per 
gram total dry matter were 463, 384, and 327 grams. The dif- 
ferences between the water losses per square inch of leaf-area, 
which were 119, 132, and 139 grams, are not very significant. 
The comparatively low ratio for the infertile soil can be explained 
at least partially by the smaller height of the plants and also 
by a somewhat slower vegetative development. 
Table 64 shows the effect in percentage of applying manure to 
the three natural soils differing in fertility. The average for the 
unfertilized potometers is in each instance used as a basis and is 
regarded as 100 per cent. The application of manure increased 
the yield of dry matter per plant in the order of infertile, inter- 
mediate, and fertile soil, 194.5, 78.7, and 41.2 per cent. The 
weight of ears was increased 296, 105.9, and 45 per cent. The 
total water transpired per plant was increased 106.7, 42.6, and 
28.7 per cent. Again in the order of infertile, intermediate, and 
fertile soil the manure reduced the water requirement per gram 
dry weight of ear 42.6, 25.4, and 10.5 per cent. The water require- 
ment per gram total dry matter was reduced 28.9, 17.1, and 8.1 
per cent. The water used per square inch leaf -area was increased 
by the manure 9.9, 12.5, and 5.2 per cent. The more infertile 
the soil, the greater was the effect of manure in increasing the 
dry matter per unit leaf-area, and in increasing the relative ear 
development in proportion to stalk. A brief summary of the 
results is given in Table 65. 
