Homework Set 3

Soils 205-90

 

1.  (6)  Explain the following pathways in the nitrogen cycle.  What are the beginning and end products, and the conditions favoring each?

 

        Mineralization-

 

 

         Nitrification-

 

 

        Ammonia volatilization-

 

 

         NH4+ fixation-

 

 

         Denitrificaiton-

 

 

         Leaching-

 

 

2.  (3) What is the source of energy for the organisms that cause:

a)  N mineralization 

b)  nitrification

c)  denitrification

 

 

3.  (2)  A gardener applied sawdust to his garden as an organic mulch.  Several weeks later his plants turned yellow and died.  Use your knowledge of the nitrogen cycle to explain in detail why this happened.

 

 

 

 

 

4.  (2)  What is the difference between symbiotic and nonsymbiotic N fixation?  Which one is more important in soils?

 

 

  

5.  (1) Describe two ways in which humans have impacted the N cycle.

 

 

 

 

6.  (1) How are deficiency symptoms of S different from those due to a deficiency of N?

 

  

 

7.  (1)  Under what conditions do soils become deficient in S?

 

 

 

8.  (3)  What forms of N, P, and S are considered plant available?

 

 

 

9.  (1) Why would elemental S be a poor choice of a S additive for a humid zone soil but might be the preferred choice in an arid soil?

 

 

 

10.  (2) What are some of the forms of P that occur in acid soils?  In alkaline soils?

 

 

 

 

11.  (2)  If the three most common forms of P in soils are plant available, why are P deficiencies so common?

 

 

 

12.  (1)  Why are N, P, and S so important to plant nutrition? 

 

 

  

13.  (1) How is the reaction of P with alkaline soils different than its reaction with acid soils?

 

 

 

14.  (3) Explain three “problems” with K nutrition.

 

 

 

15.  (1) Give an example of each of the following forms of K in soil:

  1. unavailable
  2. readily available
  3. slowly available

 

16.  (2)  In your own words (chemical reactions are not required) explain why most micronutrients are more available at low pH.  Why does Mo behave differently?

 

 

 

17.  (3)  Use the following diagram to graph the relationship between micronutrient concentration and plant growth.  Label three regions on the graph and explain the shape.

 

 

18.  (1)  What is a chelate and how does it increase micronutrient availability?

 

 

 

19.  (4)  Explain the four major goals of nutrient management.

 

 

 

 

 

 

  1.  (2) Why is the use of animal manures often considered a disposal problem rather than a fertilizer opportunity?

 

 

 

  

21.  (1) Why is rock phosphate a poor phosphorus fertilizer material?

 

 

 

22.  (1) What is the Haber Process?

 

 

 

23.  (2)  How much actual P and K (%) does a fertilizer labeled 10-23-12 contain?

 

 

 

24.  (2) How much of a 24-20-5 fertilizer material would it be necessary to apply to a field to put on 180 units of N per acre?

 

 

 

 

25.  (1) What are the disadvantages of band application of fertilizer material compared to broadcast application?

 

 

 

26.  (1) You are selecting a fertilizer for your front lawn.  Your options are fertilizer a) 45-0-0 or fertilizer b) 12-0-0.  Which one would you select and why?

 

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