THE ROTHAMSTED EXPERIMENTS 397 



The number of species found in 1903 varied from 10 on plot n-i 

 to 47 on the unfertilized plot 3. On plot 3 there were 16 species 

 varying in amount from .59 per cent to 5.98 per cent, while 3 

 species were present in large quantity; namely, 20.15 P er cen t f 

 quaking grass (Briza media), 17.45 per cent of sheep's fescue grass 

 (Festuca ovina), and 13.81 per cent of the burnet weed (Poterium 

 sanquisorbia) . For a more complete discussion of the produce 

 from The Park, see pages 150 to 189 of Director A. D. Hall's book, 

 " The Rothamsted Experiments." 



In considering the financial aspect of these experiments, 

 probably we cannot do better than to take 2600 pounds of hay, 

 the average of plots 3 and 12 for the fifty years, as a general basis 

 of comparison, and then figure the increase in the yield of mixed 

 hay at $3 per 1000 pounds, or $6 per ton, which allows more 

 than $3 per ton for the extra expense of harvesting, stack- 

 ing, baling, and marketing, and for loss, based upon the lo-year 

 average price for central United States. 



On this basis the top-dressing with $3.48 worth of acid phosphate 

 produced practically no effect, the average increase of 18 pounds 

 of hay per acre being worth about 5 cents. The use of $12.90 

 worth of ammonium salts on plot 5 produced $1.19 worth of hay; 

 but with both ammonium salts and acid phosphate (plot 4-2) the 

 increase was worth $3.98 (cost $16.38). The addition of alkali 

 salts on plot 7 has increased the yield over plot 4-2 by 2197 pounds 

 of field-cured hay, worth $6.59, but the average cost of the potas- 

 sium itself is more than $10. 



The total increase on plot n-i over the unfertilized land is 

 4900 pounds, or $14.70, while the total cost amounts to more than 

 $33. As an average the minerals on plot 7 paid less than half 

 their cost, but as an average of 40 years the wheat straw was 

 worth about $2.60 a ton as a fertilizer for the increase it produced 

 on plot 13 above plot 9; or as a substitute for nitrogen, at 15 

 cents a pound, the straw was worth $4.85 a ton. (See plot n-i.) 



An investment of $6.45 in sodium nitrate, applied alone to plot 

 17, returned $4.14; but, if the hay were figured at $10 a ton net, 

 it would have been worth $6.90, thus showing an average profit 

 of 45 cents per acre per annum, if we disregard the gradual decrease 

 in yield of the unfertilized plots, which, however, cannot be ig- 



