POT CULTURES VERSUS FIELD EXPERIMENTS 515 



same type of soil at Wooster. In one experiment the Bureau's 

 results are reported in terms of " weight of green tops " of the 

 wheat seedlings, and in the other in terms of water transpired by 

 the young plants, which Whitney and Cameron have held to be a 

 satisfactory measure of plant growth. 



It will be noted that the disagreement between the 2o-day tests 

 of the Bureau and the nine years' field results of the Ohio Station 

 is so nearly perfect as to render the short-time culture experiments 

 of no value. (See Ohio Experiment Station Bulletin 167 and Illi- 

 nois Experiment Station Circulars 105 and 123.) 



The author has repeatedly emphasized the fact that the student 

 of soil fertility should study the data secured in soil investigations, 

 and thus be prepared to draw his own conclusions. The importance 

 of this is well illustrated by the following statement from the 

 Bureau of Soils concerning the data under discussion: 



" The general conclusions from the field experiments, both in the begin- 

 ning in 1894 and in their more advanced stages, are in agreement with those 

 carried on by the methods of basket cultures and cultures in soil extract." 

 (See page 116, Ohio Bulletin 167, written by the Bureau of Soils.) 



In his introduction to Ohio Bulletin 168 (page 122), Professor 

 Milton Whitney, as Chief of the United States Bureau of Soils, 

 makes the following statement: 



"The results of the two investigations at Wooster and Strongsville leave no 

 reasonable doubt that the paraffin pot method does give results in harmony 

 with the average results obtained by the much longer timed experiments in the 

 field. It thus has an unquestionable value as a practical method for investigat- 

 ing the manurial requirements of the soil." 



Attention is called to the fact that the form of statement used 

 in Table 109 is not only entirely fair and trustworthy, but it is 

 the only method by which the effect produced by each element 

 can be ascertained for the different conditions. Suppose, for ex- 

 ample, that a farmer is using potassium alone upon his land for 

 increasing his crop yields (which, as a matter of fact, hundreds 

 of Illinois farmers are doing on peaty swamp lands). The ques- 

 tion may naturally arise, Will it pay to apply nitrogen also to the 

 soil ? According to the Bureau's results, such an addition to this 

 Ohio soil would produce a greater increase than any other addition 

 of a single element ; while, according to nine years' actual field 



