FOURTEENTH ANNUAL YEAR BOOK— PART X. 717 



are apt to be deficient in Iowa soils, can be made by any thoughtful 

 and careful farmer in the manner described in the following paragraphs: 



Essentials in a Test. In the first place, the soil on which the experi- 

 mental plots are to be located should be truly representative of the soil 

 which it is proposed to test. If this is not the case the experiments 

 will be of little value and they may even prove misleading and induce 

 the land owner to adopt a system of management which will not give 

 satisfactory results. 



Again, the land which is devoted to the experimental plots should be 

 kept, through the years, under a definite system of crop rotation. This 

 is essential because a good rotation system is the basis of nearly every 

 satisfactory soil management scheme. No particular type of rotation will, 

 of course, be used in all sections of the state. Each farmer will be com- 

 pelled to choose a rotation which he believes will give the best results 

 under existing labor, market and soil conditions. 



An excellent rotation for many sections of Iowa is the following: 

 First year — corn, 

 Second year — corn. 

 Third year — oats or wheat. 

 Fourth year — clover. 



This rotation keeps one-half of the cultivated portion of the farm 

 in corn. Many grain farmers favor this plan because corn is classed as 

 the chief "money" crop in the state, while the live stock farmers prefer 

 it because the corn crop most nearly meets the requirements of their 

 feeding operations. 



Below is given another good rotation which is especially adapted to 

 the southern and western portions of the state: 

 First year — corn. 

 Second year — oats. 

 Third year — clover. 

 Fourth year — winter wheat. 



This rotation includes winter wheat and therefore will prove par- 

 ticularly satisfactory to the large number of Iowa farmers who are now 

 growing this crop much more extensively than in former years. Wheat 

 is an excellent crop in a fertility test because it shows quite definitely 

 in yield and quality the effect of soil treatment. 



Either of the rotations referred to above may be extended to cover a 

 five or six year period by seeding timothy with the clover and using the 

 crop for pasture or meadow. 



Locating and Marking Out the Plots. — After a rotation has been de- 

 cided upon a series of ten plots should be marked off in that portion of 

 the field which is most nearly representative of the soil which is to be 

 tested. 



The plots should all be of the same size. On the average, farm plots 

 which contain one acre each will probably be found to be most satis- 

 factory. They may, however, contain one-tenth, one-quarter or one-half 

 of an acre each. The size of the plot must necessarily be determined by 

 local conditions. A long and narrow plot is usually preferred; for 

 example, a one-tenth acre plot 7\'hich is two rods wide and eight rods 



