soll.s FERTILIZERS. 15 



The investigations reported were made on 8 soil types in I differenl States. The 

 crops experimented with were cotton, |>ca>, beans, corn, and oats. The influence of 

 manure and guano and of the moisture contenl of the soil was also studied. 



By the method of washing the soils, carried through the season, and by examin- 

 ing the plant sap of the crops growing upon the soils, it was Bhown thai the recov- 

 erable water-soluble salts were materially larger where the yields were also larger. 



"The evidence here presented, taken all in all, makes it clear that, in so far as the 

 soils investigated arc concerned, there is a well-marked tendency for larger amounts 

 of water-soluble salts to be recovered by the methods adopted from the soils upon 

 which crops have made the largest yields. That the observed differences in yield 

 are due to the observed differences in the salts present in the soils i> a distinctly dif- 

 ferent matter." 



There was shown to l>e "a rather remarkable concordance between t he yields and 

 the recovered potash, indicating that the variations in the amounts of potash, in 

 soluble form in the soil, have been more influential in determining differences in 

 yields than have those of the other ingredients studied." 



///. — Relation of differences of climatological environment to crop yields (pp. 125 205, 

 ]>ls. ."> >. — This paper reports and discusses observations made during 1903, in connec- 

 tion with the investigations noted above, at Goldsboro, N. ('., Marlboro, Md., Lan- 

 caster, I'a.. and .lanesville, Wis., on some of the climatological conditions affecting 

 the -oil- an«l crops. They include records of rainfall, sunshine, soil temperatures 

 and moisture, air temperatures at 4 ft. above the soil in a corn held, and evaporation 

 from a soil saturated by capillarity, as well as "a comparative soil moisture study 

 math' on 8 soil types, in which the effect of limiting the capillar) supply of moisture 

 and of excluding the rainfall, upon the growth of corn and upon the water content 

 of the soil, [was] determined. . . . 



"In order to make a comparative study of the rate of evaporation from continu- 

 ously moist soil surfaces a soil evapori meter was- constructed from galvanized iron in 

 the form of a cylinder, with closed bottom, 2 ft. deep, which was sunk in the field. 

 . . . The cylinder luul a diameter of 4 ft. and was arranged in such a way that an 

 automatic record of the rate of evaporation might he obtained by the use of a wain 

 register. . . . 



The evaporimeters . . . were all filled with soil from the unfertilized subplots, 

 using soil from the surface !» in. The soil was introduced in layers about 2 in. thick 

 and firmed so as to secure about the normal weight per cubic foot for the soil in 



place. 



"At the bottom of the evaporhneter there was a water reservoir, rising to the height 

 of 1 ft., upon which the shelter for the water register rested. Water could he added 

 to or removed from the reservoir as desired. Upon this water surface rested the 

 float of the water register. Before introducing the soil the bottom of the evapo- 

 rimeter was covered with a layer of sand or gravel, thus providing a medium through 

 which the water could spread easily and uniformly under the whole soil surface. 

 The level of the surface of the soil in the evaporimeter was about 2 in. below that of 

 the rim, and was left linn, smooth, and horizontal, and was kept free from all plant 

 growth throughout the season. The level "f the water in the reservoir was usually 

 maintained at about 1 ft. below the surface, water being added once per week and 

 removed when made necessary as the result of rains." 



A set of similar evaporimeters 4 ft. deep and having a larger reservoir were used 

 for studying evaporation from corn plants grown on the different soils. 



In order "to ascertain in how far the soil moisture contained in the soil at the 

 beginning of the growing season is capable of carrying a corn crop toward maturity 

 when no rain is allowed to fall upon the ground, and what the yields would he . . . 

 2 blocks of soil on each of the 2 soil types at each of the 4 stations were cut off from 



