862 ANNUAL, REPORT OF THE Off. Doc. 



DISCUSSION OF MARYLAND STATION RESULTS. 



The matter of drawing conclusions from results obtained from 

 plot experiments is always attended with more or less uncertainty, 

 as soil and weather variations will often bring about what may seem 

 to be contradictions. There are, also, often uncontrollable and 

 unnoticed errors produced by the depredations of birds, mice, in- 

 sects, etc. While these may be very small in themselves, yet when 

 the error is multiplied to represent yields per acre, it may amount 

 to considerable. In order to obviate some of these difificulties, 

 there has been no report made on the experiments under discussion 

 until they have been through five years, and covered several kinds 

 of crops. Even a longer period than this would be desirable, as 

 it would probably serve to confirm some conclusions and to eliminate 

 some doubtful points. These tests will be continued for some years. 



The quantities of phosphoric acid applied in these tests are rather 

 more than was necessary and more than would be found economical 

 in practice, but it was thought best in planning the experiments 

 to have an excess present and so endeavor to make the results more 

 pronounced, than to attempt to run on the basis of greatest profit. 

 It was the principles of phosphoric acid fertilization that were de- 

 sired to be established rather than the limits of the soil require- 

 ments. 



Nothing Plots (Nos. .5, 10, 15, 20). An examination of Table 19, 

 page 62, shows that the average total product from the plots re- 

 ceiving no fertilizer was considerably below the average yields of 

 all the plots which were fertilized. With some crops there was 

 little increase in the yield through fertilization, and in a few in- 

 stances the nothing plots made a slightly higher yield than those 

 fertilized. This is notably the case with corn. The unfertilized 

 plots of corn made a better average yield than those receiving the 

 soluble phosphoric acid with rye turned under. The failure of the 

 phosphoric acid plots to outyield the nothing plots was probably due, 

 in a measure, to the phosphate being very available to the plant, 

 over-stimulated it in the start, and this produced in the plant a 

 condition which made it not so able to withstand the period of 

 drought later in the season and at a time when the grain was form- 

 ing and there was greatest call for food and activity. This is borne 

 out in a measure by a comparison of the detailed yields as given in 

 Table 19, v.ith the rainfall for that period. There is also a proba- 

 bility that the soluble phosphoric acid, when it entered the soil, 

 was precipitated and formed unions which were not available to the 

 crops, but this condition would not likely produce a decrease in the 

 yields. All of the fertilized plots made very decidedly larger yields 



