SOIL IMPROVEMENT 87 



white cloudy appearance. If bone and phosphate rock were 

 in the soil, would they be dissolved by rain? 



EXERCISE. Dissolving Superphosphates. Put a very 

 little superphosphate (or acid phosphate) from a fertilizer 

 sack in a glass of water and stir. Does any of it dissolve? 

 Add a little clear lime-water. It should make a white cloudy 

 appearance, showing that some of the material has dissolved. 

 This would mean that plants could use this form of fer- 

 tilizer. 



Problems. 1. If nitrate of soda is 16 per cent nitrogen, 

 how many pounds of nitrogen in a ton of it? 



2. If sulphate of ammonia is 20 per cent nitrogen, how 

 much of it would be required to supply a 12-acre field with 

 240 pounds of nitrogen? 



3. When available phosphoric acid is valued at 5 cents 

 per pound, what should be the cost per ton of mineral super- 

 phosphate which is 14 per cent available? What should it 

 cost per ton if it is 20 per cent available? 



4. A shipment of sulphate of potash contained 48 per cent 

 potash, which should sell at 5 cents per pound of potash. 

 What will be the selling price per ton of this fertilizer? 



REVIEW. 



1. Give four kinds of improvement for soils. 



2. Give two kinds of tillage and the implements used for each. 



3. Give all the objects of plowing. 



4. Describe the different forms of mouldboards and the special 

 use of each form. 



5. What is a gang plow? 



6. Give several reasons for fall-plowing. 



7. Give a general rule governing the depth to plow. 



8 Describe a system of preventing weeds by shallow tillage. 

 9. Give the benefits derived from green manures. 



10. What care should be exercised in the use of green manures? 



11. Give the effects of lime on light soils. On heavy soils. 



12. Give five other effects of lime. 



13. Give five things which influence the value of barnyard manure. 



14. What are the two main causes of loss in stored manures? How 

 great is the loss usually? 



15. Describe two good ways of storing manure. 



