FIELD EXPERIMENTS WITH FERTILIZERS. 



W. H. Jordan. 



One of the oldest, and evidently one of the most popular, classes 

 of experiments conducted by experiment stations is field experi- 

 ments in the use of fertilizers. The Maine Station has shared 

 with other stations in this work and is now tilling experimental 

 plots for the eleventh season. 



Afier experience for this length of time, the writer is obliged to 

 confess that the results obtained, although valuable enough to be 

 well worth securing, are not so satisfactory as are those obtained 

 along some other lines by more accurate and severe methods. 

 Field experiments of whatever kind are not subject to exact con- 

 trol. They are widely open to sources of error, and for this reason 

 they are difficult of safe interpretation. The publication of a 

 single season's results is justified only on the ground of a pardon- 

 able ambition to show what and how much a station is trying to 

 accomplish, but to draw hard and fast conclusions from one year's 

 results is rarely warranted. After ten years have elapsed, how- 

 ever, the accumulated data possess a significance not possible in 

 the early stages of the work. There are presented here therefore, 

 not only the unpublished data of several years work but also a 

 summary of results secured during nine years. 



The problems that have been studied through field experiments 

 with fertilizers are those that are plainly indicated by practical 

 work as the important ones. 



(1) The relative utility of different forms of phosphoric acid. 



(2) The effect of partial and complete fertilizers.* 



(3) The relative effect of different amounts of fertilizer. 



(4) The possibility of maintaining fertility by the use of com- 

 mercial fertilizers alone. (Systems of manuring.) 



The matter of profit is not immediately connected with these 

 experiments. Indeed it is not possible to order them with refer- 

 ence to profit, consequently in their discussion the cost of produc- 

 tion is not considered . 



*The term complete is used liere as meaning a fertilizer that contains nitrogen, 

 phosphoric acid and potash. Such a fertilizer mixed in a particular manner, 

 xnay or may not be complete in the sense of supplj'ing the needs of a crop under 

 given conditions. 



