248 SOILS AND FERTILIZERS 



QUESTIONS 



1. What advantage is gained by alternating deep-rooted with 

 shallow-rooted plants in a rotation ? 



2. Why is a rotation of crops less likely to cause a deficiency in 

 some one constituent of the soil than is the continuous growt^L of 

 one crop ? 



3. In what ways do some crops and some crop treatments pre- 

 pare available nutriment for other crops ? 



4. How may soil structure be affected by crop rotation ? 



5. Explain the relation of crop rotation to weeds. 



6. Explain the relation of crop rotation to plant diseases and 

 insects. 



7. How may plant nutrients be prevented from leaching by the 

 use of the proper rotation ? 



8. What three classes of crops should have a place in any rota- 

 tion and why ? 



LABORATORY EXERCISES 



Exercise I. — Crop rotations. 



Study standard crop rotations from different parts of the United 

 States as to crops grown, climate, markets, fertility of the soil, 

 fertilization, etc. Try to find the reason for the use of each rotation 

 under its particular conditions. , 



With the aid of the pupils, obtain a number of the rotations used 

 in the community or county. Study these from all standpoints, 

 and, if possible, suggest improvements. A rotation survey of the 

 community might be made in order that data valuable to the 

 farmers, as well as to the pupils, shall be obtained. The students 

 should aid in this as well as in the tabulation and interpretation of 

 the data. 



Exercise II. — Fertilizing the rotation. 



Under given conditions have the pupil work out the fertilization 

 of a standard rotation for the locality. This means not only the 

 kinds and quantities of fertilizer to apply, at what point in the 

 rotation to add them and at what time of year to put on the soil, 

 but also the use of lime, green manure and farm manure. Such a 

 study should be a summation of many of the practices and principles 

 of good soil management. 



