242 Report on Ckop PROcrcTioN of the 



productive capacity in every part and untoward conditions such 

 as fungi and injurious insects were to affect one part no more 

 than another, then we could measure with great accuracy the 

 relative influence of different fertilizers or different quantities of 

 the same fertilizer. Such desirable conditions as these are not 

 to be found. Only approximate accuracy is reached in field 

 experiments, even under the most favorable circumstances; and 

 for this reason the accompanying figures should not be taken as 

 representing fixed or absolute relations. The experiments con- 

 vey lessons, however, which appear to the writer to be plain. 



In the first place it is entirely clear that the limit of produc- 

 tion as determined by season and other conditions outside of the 

 supply of food was nearly reached in the Purdy field with the 

 first 500 lbs. of fertilizer applied. This is equivalent to stating 

 that the profits were mostly realized from the first 500 lbs. of 

 fertilizer, the manure cost of the gain in yield being only 1G.6 

 cents per barrel. While with the increasing quantities of fer- 

 tilizer used there was on the average a corresponding increase 

 of crop, this greater production but very little more than paid 

 for any application of fertilizer above 500 lbs. The data show 

 that the additional yield of onions resulting from each 500 lbs. 

 increase of fertilizer above the first 500 lbs. had a fertilizer cost 

 of 10.79 to 12.28 per barrel. The profits of such manuring are 

 uncertain, depending upon market conditions. 



It is to be noticed, moreover, that the added growth due to the 

 first 500 lbs. of fertilizer was not uniform in the different years. 

 In 1900 conditions were favorable for an onion crop, a fairly 

 large yield being secured, and the highest returns of any year 

 were obtained from the commercial plant-food added to the soil. 

 The year 1898 gave the smallest crop of any of the four. Com- 

 paring the effect of the fertilizers in these two years, we see that 

 500 lbs. of fertilizer caused an increase in 1900 of 64. G bbls. of 

 onions per acre and in 1898 only 11.7 bbls. It should be noted 

 that in 1898 the yield, though small, was progressive with the 

 increase of fertilizer, while in 1900 the yield with 500 lbs. of fer- 

 tilizer was as large as with the heavier manuring. All this 



