QUESTIONS 225 



with moisture, has the ability to dissolve organic matter. This accounts in a 

 large degree for the brownish color of barnyard water. 



We can observe this solvent action in the following experiment: 



Place a good tablespoonful of organic matter (peat) provided in each 

 of two flasks, and add 75 c.c. of ammonium carbonate solution to one and a 

 like amount of water to the other. Shake each well for five minutes, then let 

 stand for 20 minutes, after which time shake again for a few seconds. Run 

 the liquid contents through filters into tumblers and note color of liquids. 

 Explain results. 



Home Experiments and Projects. To determine the profitable use of 

 acid phosphate on soil deficient in phosphorus. 



Procedure. Apply 300 pounds of acid phosphate on an acre of soil needing 

 phosphate. Another acre beside this should be left unfertilized. Keep account 

 of all costs, measure yields, and compute net profits. (One-tenth acre plots 

 could be used as well.) 



Other Fertilizer Projects. To determine the effect of an application of 

 mixed fertilizer applied on corn at the rate of 125 or 150 pounds per acre, in 

 the hill, with a fertilizer attachment on the corn planter. A whole field of 

 corn may be fertilized in this manner, but leave at least 4 or 6 rows through the 

 field for a check. Determine increased yields at harvest time, and determine 

 profits in the use of the fertilizer (Figs. 137 and 138). 



Tests may be made determining: 



(a) The value of green manuring on sand or on any soil poor in organic matter. 



(6) The value of manure reinforced with acid phosphate. 



(c) The more economic use of manure when applied at the rate of 8 tons 

 per acre over a 16-ton application. Keep account of all costs, determine yields, 

 and compute net profits. 



QUESTIONS 



1. Discuss the importance of available plant-food elements in relation to 



soil fertility. 



2. What are the elements most considered in crop production? 



3. What materials in a virgin soil contribute to the crop requirements of 



nitrogen, phosphorus and potassium? Is this supply inexhaustible? 



4. What is the theory of fertilizers? 



5. What are the substances commonly used to add needed elements to soils, 



or to render more available what is there? 



6. Of what value is leaf -mold, grass, etc.? 



7. What is meant by green-manuring? What are the benefits to be derived 



through this practice? 



8. Does green-manuring ever prove profitable? Is it always necessary to 



apply green manure? 



9. What are the best kinds of green manuring crops? Why? 



10. Why is it important to maintain the organic matter in soils? 



11. Name some crops used in green-manuring. Discuss their adaptability to 



different conditions. 



12. What are some points to bear in mind in plowing under green crops? 



13. What crops usually follow green-manuring? Why? 



14. Discuss the importance of green-manuring in soil improvement. 



15. What should determine whether or not a crop should be plowed under 



instead of being cut for hay? What is rowen? 



15 



