Transpiration as a Factor in Crop Production. 
143 
RELATION OF SOIL FERTILITY TO GROWTH AND WATER 
REQUIREMENTS OF CORN. 1 
Two different series of soil fertility potometers have been 
operated and are reported in this paper. (1) The first of these 
was started in 1911, one year's results having been published. 2 
The soil used in the initial filling of the potometers in 1911 has 
remained undisturbed thruout the past four years. A crop of 
corn has been harvested from it each year, and the yields and 
water requirements have been determined. (2) The second 
series was commenced in 1914, and was similar in plan to series 
No. 1 except in the degree of soil fertility. 
In each experiment three soils were used, representing low, 
medium, and high fertility. Eight duplicate potometers of the 
subirrigation type were filled with each kind of soil, four of wnich 
received an application of well-rotted sheep manure, thoroly 
mixed with the upper 10 inches of soil. The other four potometers 
of each group remained untreated. Manure was applied in both 
experiments at the rate of 4 pounds per potometer, which was 
equivalent to approximately 21 tons per acre, wet weight, count- 
ing 10,668 plants per acre grown three per hill, with hills 3.5 
feet apart. Reduced to a moisture-free basis, this manure 
application was 2.4 pounds per plant in 1911 and 1.75 pounds in 
1914, which equaled respectively 13 tons and 9 tons of moisture- 
free manure per acre. 
The average composition of the different soils used is given in 
Table 59, while the total amount of plant food elements contained 
in each potometer is given in Table 60. 
The soils may be briefly described as follows: 
(1) Infertile soil. This has been classified as Lancaster Fine 
Sandy Loam, and was taken from a cornfield of low productivity 
five miles distant from the Agricultural Experiment Station. 
In the 1911 experiment the soil was refilled in the potometers 
in 6-inch layers as they were taken from the soil, while in 1914 
only the surface 10 inches of soil was used. 
(2) Fertile soil. This was Wabash silt loam taken in 6-inch 
layers in 1911 from a native pasture of the Agricultural Experi- 
1 References concerning the relation of transpiration to soil fertility: 
Briggs and Shantz (1914), Heinrich (1894), Hellriegel (1883), Kiesselbach 
(1910), King (1893, 1894), Lawes (1850), Leather (1910, 1911), Liebscher 
(1895), Maercker (1896), Marie-Davy (1874, 1875, and 1876), Montgomery 
and Kiesselbach (1912), Ohlmer (1908), Pfeiffer et al. (1912), Preul (1908), 
Schroeder (1896), Seelhorst (1899, 1906, 1907, 1910), Seelhorst and Biinger 
(1907), Sorauer (1883), Thorn (1913), Widtsoe (1909), Wilfarth and Wimmer 
(1902), Wilms (1899), Wimmer (1908), and Willard and Humbert (1913). 
2 Montgomery and Kiesselbach (1912). 
