6 MASS. EXPERIMENT STATION BULLETIN 290 



since the field was first plowed in 1883. Ail the other plots received equal amounts 

 of nitrogen, but in different kinds of fertilizers. Plot was again included. For 

 this year it is sufficient e.xplanation to mention that all the plots received fer- 

 tilizers supplj'ing phosphoric acid and potash in amounts like those of 1885, 

 while all but three received nitrogen as in that year. 



We have then a crop of corn liberally fertilized which can be compared with 

 the first crop on immanured soil. It will be noted that not one of the plots 

 equals the first year, with the exception of 10, which in total crop barely exceeds 

 its first year. In all cases the yields of ears are lower in this fertilized crop. The 

 crop of 1883 was grown upon new land, even though it was "run out" as a pro- 

 ducer of hay. The turf underlying that corn evidently contained a reservoir of 

 fertility fully equal to that added in the fertilizers of 1889. The poor yields on 

 Plots 4, 7, and 9 are especially striking and will be recalled later in this article. 



In the report for 1889, there is the statement that the larger part of the late 

 summer was cold and wet and for this reason unfavorable for raising fodder corn. 

 A difference in average temperature between the two seasons would affect the 

 development of the corn crop in a way that could not be wholly overcome by 

 fertilizers. The first crop was frost-bitten early in September, which would cause 

 a quickened drying of the leaves and possible losses by breakage of them in 

 handling. Hence we have in each season under comparison a weather condition 

 which cannot be evaluated in weight of crop. 



During the recorded history of this field there have occurred variables which 

 have affected the field unevenly for a tim^e. The most common variables were 

 weather conditions such as a drenching rain at a critical stage, an unseasonable 

 frost, a severe drought, or a hard winter. Theoretically, all parts of a field are 

 equally exposed to the weather. Actually, variations in soil or fertilizers are 

 much exaggerated by an e.xtreme change in weather. Sometimes the variable 

 was due to the lack of facilities encountered in pioneer work as in these early 

 e.xperiments. 



It is now well known that it is difficult to find a field of an acre or more that 

 is truly uniform in soil and subsoil throughout its area. This experimental field, 

 like the experiment station itself, has developed under changing conditions 

 which could not be foreseen and to which adjustments were necessary. 



COMPARISON OF NITROGEN FERTILIZERS 



Beginning in 1889 and continuing with but little change until 1919, a fer- 

 tilizer ex-periment was planned with the object of comparing three distinct kinds 

 of nitrogen fertilizers represented by the standard chemicals of that period, viz., 

 sodium nitrate, ammonium sulfate, and dried blood. The other essential elements 

 of soil fertility, phosphoric acid and potash, were supplied to all plots alike in 

 standard chemicals of the times. Phosphoric acid was contained in dissolved 

 boneblack. Potash was applied in two distinctly different compounds, muriate 

 of potash and sulfate of potash-magnesia. In the long run this comparison of 

 two potash compounds showed them to be equally effective and cannot be said 

 to have influenced the comparison of the nitrogen fertilizers. 



The quantities of chemicals for the different plots are given in the following 

 chart. In terms of poimds per acre they would contain 45 pounds nitrogen, 80 

 pounds available phosphoric acid, and 125 pounds potash. In 1894 and 1895 the 

 quantities of phosphoric acid and potash were doubled but with no appreciable 



