A THIRTY-YEAR FERTILIZER TEST. 133 



have been the same for the two series of corn years; and the destructive 

 system of farming followed may have seriously affected the ability of the 

 soil to produce crops on fertilizers alone, as compared to its ability to pro- 

 duce crops on barnyard manure. 



With reference to the first possibility, Table 6, page 136, presents data 

 for moisture and temperature during all of the years in question. An 

 attempt is made to epitomize these records in a single sentence descriptive 

 of the growing conditions for the years in question. Bringing these to- 

 gether, the following picture is obtained of the comparative growing 

 conditions in the two periods : — 



It is evident that the weather conditions in the last period were less 

 favorable than in the first period. 



In interpreting the significance of the above facts, thought must be 

 given to the farming system followed. At the very beginning the stage 

 was apparently set, although unconsciously, for a crop increase from the 

 use of fertilizer potash. Grass, a heavy potash feeder, had been occupy- 

 ing the land for a number of years, but without return to the soil of either 

 manure or fertilizer. As the years passed, this initial condition was 

 accentuated through the removal from the soil of successive crops of corn 

 and of grass and clover. Had these crops been fed on the farm, as in 

 practical agriculture they must have been, there would have been potash 

 return to the soil by natural means and less need for the use of commercial 

 potash. 



The Destructive Treatments. — A number of treatments were definitely 

 destructive, i.e., j-ields decreased definitely and significantly from one 

 period to another, and reached a point at which profitable farming would 

 have been absolutely impossible. Nitrate of soda alone, acid phosphate 

 alone, lime alone, nitrate of soda and acid phosphate, and land plaster 

 come in this Hst. The average jields for the first and second periods for 

 plots treated with these materials were as follows : — 



