115 



much as one half ration of potash and never over one-fifth ration of nitro- 

 gen, while the plot experiments have undertaken to supply full rations for 

 a full crop, which is fully double an average crop. 



The quantities of fertilizer used in the plot tests mentioned above 

 seem quite absurd to the American grain grower, yet they are very con- 

 servative compared with another set inaugurated at about the same time 

 in which 2,000 pounds of acid phosphate, 600 pounds of sulphate of potash 

 and 600 pounds of sulphate of ammonia per acre were used, or with an 

 extensive set of orchard experiments in which the plans called for the 

 application of 40 pounds of muriate of potash with corresponding amounts 

 of nitrogen and phosphates to each two year old tree. 



In the case of the plot experiments conducted for the purpose of de- 

 termining the value of the different plant foods, the excessive quantities 

 have often caused a profit to be shown for only the particular plant food 

 which was most deficient, while if more reasonable quantities had been 

 used each would have shown a profit. It is not unusual to find reports 

 of these experiments that recommend the use of a single plant food as all 

 that is necessary merely because it was the one that chanced to give the 

 largest profit. 



As compared with this line of plot experiments with full rations we 

 may, perhaps, devote a moment to results of plot experiments where 

 amounts and formulas generally used in farm practice were taken as a 

 basis. 



On a typical worn clay wheat land an experiment was undertaken on 

 the basis of 300 pounds per acre of goods containing nitrogen 3 per cent, 

 available phosphoric acid 10 per cent and potash 6 per cent, each element 

 being omitted in turn in the usual way. 



The following results were obtained : 



Fertilizers applied 



Yield, 

 bushels 

 per acre. 



Reduction from Omitting 



Equal to — 



Nitrogen. 



Phos. Acid. 



Potash. 



All. 



300 lbs. 3-10-6 



300 lbs. 0-10-6 



300 lbs. 3-0-6 



300 lbs. 3-10-0 



None 



33. S 

 29.1 



7.6 

 25.0 



6.5 



4.7 



26.2 



S.8 



27.3 



