220 SOILS AND FERTILIZERS 



to amounts and mixtures is generally different for different farms, 

 the place of fertilizers in a standard rotation is more or less fixed. 



Take a number of good practical rotations and indicate where in 

 the succession of crops the fertilization should occur. Also suggest 

 what should be the formula of each mixture used, the fertilizer 

 compounds which should be carried and the amounts that might 

 be applied to a given soil. 



Exercise II. — Fertilization of home-farms. 



Encourage the pupils to bring in data regarding the fertilization 

 on their home farms. Tabulate, discuss and criticize such data in 

 a practical way. If any of the pupils have home project gardens, 

 the fertilization of such gardens should be made a special problem 

 for them. 



Exercise III. — Fertilizer practice in the community. 



A fertilizer survey of the township could be made with profit 

 by the teacher, visiting each farmer and making inquiry adequate 

 for the purpose in view. The pupils could aid not only in the col- 

 lection of such data but also in such compilation and interpreta- 

 tion as would later be necessary. 



Taking the class to visit a farmer whose system of farming and 

 fertilization is a practical success is to be advocated. The 

 economic use of fertilizers is attained not only by scientific knowl- 

 edge, but also by good sound experience and practice. 



Exercise IV. — Fertilizer experimentation. 



The measurement in crop yield of the effects from fertilizer use is 

 the only true means of gauging fertilizer needs and fertilizer prac- 

 tice. Whether a certain fertilizer pays is the ultimate question. 



Jjay out plans for fertilizer experimentation as suggested in the 

 text with the idea of taking careful data as to crop yield from the 

 various treatments used and the calculation of the net returns. 



The fertilizer needs of the soil for nitrogen, phosphoric acid, 

 potash and lime may be determined by the use of the various fer- 

 tilizer carriers both alone and in combination. Different ready mixed 

 fertilizers may also be compared. The amount of any particular 

 fertilizer that may most economically be used can be tested by vary- 

 ing the applications of the same mixture. The relation of lime, farm 

 manure and time of application to the effectiveness of any particu- 

 lar fertilizer may also be made a subject of experimentation. 



