Commercial Fertilizers. 169 



of the rotation. This method is used especially where only one 

 crop in a rotation is sold, the others being fed on the farm. A 

 liberal supply of food is used to give the maximum yield which 

 the climate and season will permit. The amount of food applied 

 is in excess of the requirements of the crop and the residue is 

 depended upon to help nourish the succeeding crops, or at least 

 the one immediately succeeding the money crop. This system 

 has some valuable features and is probably the one most in use 

 in this country at the present time. 



"Too frequently fertilizers are used by what certain writers 

 have called the 'hit or miss' system. No special thought is given 

 to the requirements of the crop or the composition of the fer- 

 tilizer, but if a farmer feels that he can afford it and the agent 

 is a glib talker, the sale is made. If the buyer happens to 'hit' 

 the food requirements of his crop a profit is secured and he is 

 correspondingly happy, while if he makes a 'miss' he feels as- 

 sured that there is no value in commercial fertilizers." Viv- 

 ian.) 



Field experiments necessary. These systems described have 

 their good features, but they do not take into account the' import- 

 ant fact that soils differ greatly in the amount and availability of 

 the plant food they already contain. In order to determine with 

 any degree of certainty what particular constituents are needed 

 the farmer must conduct some experiments for himself. This 

 can be done by carefully marking off certain portions of the 

 field, of definite size and uniform soil, and using on them differ- 

 ent fertilizing materials. Plots one rod wide and 8 rods long, 

 and containing 1/20 of an acre, are of convenient size. The dia- 

 gram on page 170, taken from Vivian, shows the arrangement 

 and kinds and quantity of materials to be used on each plot. 



Careful notes should be made during the growing period and 

 at the end of the growing season and when the crop is harvested 

 comparison made as to the yields by weight obtained. In this 

 way definite information will be secured as to whether the soil 



