Fertilizers for Cereals and Grasses 215 



The farmer must study his own conditions. Scientific 

 inquiry has established the facts that soils differ in their 

 content of the different plant-food elements, and that 

 those of practically the same chemical composition differ 

 in respect to their physical qualities, which conditions 

 exercise an important influence upon the availability of 

 the constituents. 



This experimenting may also seem to be a trouble- 

 some operation, yet, if thoughtfully managed, it will 

 mean but little extra labor, and the resulting gain may be 

 far in excess of the cost of the work. For example, if it is 

 shown that fertilization under certain conditions is not 

 needed, and therefore not profitable, it saves possible 

 outlay at once ; if it shows that the application of certain 

 of the constituents is a profitable practice, it enables the 

 adoption of a systematic scheme of fertilization. 



A scheme for plot experiments. 



The following simple scheme of plot experimenting 

 has been suggested, and it admits of determining many 

 of the points involved. This scheme includes ten plots, 

 in which three are to be cropped without manure, as 

 check plots, in order to show the productive capacity of 

 the unmanured land. The plots may vary in size, though 

 it is desirable that they should contain at least one-twen- 

 tieth of an acre, and that they should be long and narrow 

 (one rod wide and eight rods long is a size), in order to 

 include as many inequalities of the soil as possible ; though 

 in any case land as uniform as possible in physical and 

 chemical qualities, and fairly representative, should be 

 selected. The following plan permits of a study of the 

 effect of the application of individual constituents, and 

 of their various combinations. If desired, in order to sim- 



