212 ANNUAL REPORT OF THE Off. Doc. 



located merely upon a plot of tive hundred acres up in Centre 

 county, but that its boundaries are coincident with the boundaries 

 of the State. How this work may best be accomplished is a matter 

 of detail which will recjuire careful consideration. 



Having located the soil types and having found that these soils 

 have different crop adaptation or require different cultural methods, 

 the question still remains, why these differences. What is the 

 c?use? We say in academic language that to produce ordinary 

 crops there is needed light, heat, water and plant food. There is no 

 doubt whatever, that these things are needed. When, how- 

 ever, we look at plots of ground, one of which yields twice as much 

 as the other and we ask ourselves, v/hat v>'as the variable fact(;r 

 in the production of these crops, we are uncertain as to the answer. 

 Was it the light, the heat, the water, or the plant food, or was it 

 due to some deleterious substance excreted by the plant. The 

 thought that it is desired to develop here may perhaps be illustrated 

 by an example. In the rotation fertilizer experiment at the Penn- 

 sylvania Station plot No. 1 in the second tier has received no fer- 

 tilizer or manure of any sort since the beginning of the experiment 

 in 1882, while plot No. 9 of the same tier has received a complete 

 commercial fertilizer each year; that is, whenever this plot was in 

 coru or wheat but not when it was in oats or grass (timothy and 

 clover). During the whole period the yield of plot 9 was 160, com- 

 pared with 100 for plot 1, aisd last season the yield of plot 9 was 

 197, compared with ioO for plot 1, or a yield of 23.2 and 12 bushels 

 respectively. The only difference in the treatment between these 

 two plots was the application .of fertilizer containing nitrogen, 

 phosphoric acid and potash. Was the difference in yield merely a 

 matter of i)lant food or was there a variation in some of the other 

 necessary factors of plant growth? By installing self-recording 

 thermometers on these plots Brown has shown in data to be pub- 

 lished in the next annual report of the Experiment Station that the 

 tem])erarure of the soil at sis inches below the surface was the 

 lowest on the high yielding plot in the summer and highest on this 

 plot in the winter, and that at all seasons of the year the extremes 

 in temperature were less on the high yielding plot. It will not do 

 to say that the difference in yield was due to differences in tem- 

 perature, but it is not unreasonable to believe that the difference 

 in temperature was a factor in producing the results. At any rate 

 it is a good illustration of the complicated character of the problem 

 before us. 



There are in this rotation fertilizer experiment, which was begun 

 in 1882, 144 plots which have received twenty-three distinct treat- 

 n^ents. These plots after twenty-five years show most marked 

 variations in the yield of corn, wheat, oats and hay, due to the 

 diff'erent fertilizers applied. While the crop is growing, it seems 

 that the soil should exhibit some differences, either in heat, mois- 

 ture, plant food or in some deleterious or toxic material. The 

 problem, then, is to study the soil as it is found under normal con- 

 ditions, not only as to heat, as has just been illustrated, but as to 

 moisture, plant food and toxic material. If, for example, the ap- 

 plication of fertilizer is valuable, not alone because it furnishes 

 plant food but because it destroys substances injurious to the plant, 



