THE ROTHAMSTED EXPERIMENTS 363 



Ross of Alabama, Peter of Kentucky, and Penny of Pennsylvania, appointed 

 by the Association of Official Agricultural Chemists, "to consider in detail 

 the questions raised"; published in full in Circular 123 of the University of 

 Illinois Agricultural Experiment Station.) 



BROADBALK FIELD 



Undoubtedly Broadbalk is the best-known experiment field in 

 the world, and plots 2 and 3 are the most often referred to. While 

 the continuous growing of wheat on the same land is not to be 

 considered the best practice, the records given in Table 60 show 

 very clearly that it is possible. These plots are compared with 

 most of the others for a period of 55 years. Perhaps the most 

 interesting and instructive results are the average yields of 12.9 

 bushels on the unfertilized land, 35.5 bushels with farm manure, 

 and 37.1 bushels with the heaviest applications of commercial 

 plant food. 



Plots 5, 6, 7, and 8 differ only in the amount of nitrogen applied; 

 and, with successive additions of 43 pounds of nitrogen per acre, 

 the average yields increase from 14.9 bushels with no nitrogen 

 applied, to 23.8 bushels with 43 pounds of nitrogen, to 32.8 bushels 

 with 86 pounds of nitrogen, and to 37.1 bushels with 129 pounds 

 of nitrogen. The average yield of 55 crops is only 2 bushels more 

 per acre where 792 pounds of mixed mineral fertilizers have been 

 applied every year than where no fertilizer of any kind has been 

 used. These data are in striking contrast with the results from 

 Agdell field, where, as an average of the last 20 years, the increase 

 with minerals alone is 83 per cent of the total increase with min- 

 erals and nitrogen, while on Broadbalk the minerals alone have 

 produced an average increase which is only 8 per cent of the in- 

 crease from minerals and nitrogen (plot 8). 



With the fallow system on Agdell field the results are tending 

 in the same direction as those from Broadbalk, and most markedly, 

 of course, where all crops were removed. 



This must emphasize a fact which it is exceedingly important to 

 keep in mind while studying the results from Broadbalk field; 

 and indeed, when studying the data from not only the Rothamsted 

 fields but from nearly all of the oldest soil experiment fields in 



