Soil Fertility 97 



QUESTIONS 



1. Why should green-manure or farm manure or both be used with 

 commercial fertilizer ? 



2. How many pounds of nitrogen, phosphoric acid, and potash are 

 present in a 3-6-4 fertilizer ? How many pounds of ammonia, phos- 

 phorus, and potassium? 



3. State the five benefits of lime for soil improvement. 



4. What are the advantages in using ground limestone in place of 

 caustic lime ? 



5. How can a soil be tested to learn whether or not it requires lime ? 



6. Why should soil to be planted to alfalfa or red clover be well 

 limed? 



7. For what kind of crops is commercial fertilizer especially use- 

 ful? 



8. What is the appearance of growing plants that are in need of 

 nitrogen? 



9. Why should dried blood and tankage be mixed with the soil 

 in the furrow before the seeds are planted? 



10. When should raw rock-phosphate be used in preference to 

 treated phosphates? 



EXERCISES 



1. Fertilizer laws. Write to your experiment station for copies 

 of the fertilizer laws of your state. Study these carefully. 



2. Home-mixing of fertilizer. Find the quantities of material 

 required to mix a 2-8-6 fertilizer from 15 per cent nitrate of soda, 14 

 per cent acid-phosphate, and 50 per cent sulfate of potash. Make up 

 other similar problems. Get a fertilizer formula from a bag of mixed 

 fertilizer and plan how you could mix one having the same formula. 



3. Testing soils for acidity. Following directions given in the 

 chapter, test the soil in several fields near the school-house for acidity. 



REFERENCES 



Same as Chapter III. 



