THE ROTHAMSTED EXPERIMENTS 385 



used in these computations is 50 cents a bushel (57.6 cents being 

 the lo-year average farm price for New York State, and also for 

 Ohio), and the cost of manure is figured at $2 a ton; but these 

 figures should always be modified to meet average local conditions. 

 They only help to summarize the results so as to bring to mind 

 their economic importance. 



Thus, at the prices named, the treatment applied to plot 4 has 

 cost $35.32 a year, and the increase produced has been worth $70 

 a year, or sufficient to pay the cost and leave practically 100 per 

 cent net profit. 



The ammonium salts on plot 5 have paid but half their cost, and 

 the sodium nitrate alone has but slightly more than paid for itself. 

 By far the largest returns for money invested has been from acid 

 phosphate on plot 9, which has paid for itself and added more than 

 600 per cent net profit as an average of the 26 years. Indeed, the 

 acid phosphate alone exactly doubled the average yield of 26 years. 



The alkali minerals, including 300 pounds of potassium sulfate, 

 100 pounds of magnesium sulfate (Epsom salt), and 100 pounds of 

 sodium sulfate (Glauber salt), have not paid their cost when used 

 in addition to acid phosphate, the average annual increase of plot 

 10 over plot 9 being only 7 bushels, and the annual cost $7.90. 



The largest average yield and the largest net profit per acre is 

 from plot 8, which produces as much on one acre as were grown on 

 four acres of untreated land. It should be noticed, however, that, 

 during the last 10 years of the experiment, the farm manure plots, 

 3 and 4, have forged ahead of the complete chemical fertilizers on 

 plots 7 and 8. 



Director Hall makes the following statements in his book on 

 " Rothamsted Experiments " (1905) : 



"In the Hoos field, experiments upon potatoes were begun in 1876, and con- 

 tinued for twenty-six years ; they were then discontinued, because the crop on 

 the plots receiving no organic manures had fallen to a very low ebb in conse- 

 quence of the deterioration of the texture of the soil. But on the plots receiving 

 farmyard manure, and even on those receiving only a complete artificial manure 

 (plots 7 and 8), the crop was maintained in favorable seasons. No falling off 

 was observed which could be attributed to the land having become 'sick' 

 through the continuous growth of the same crop, or through the accumulation 

 of disease in the soil." 



