Ahs2208:Soil Science Ii Question Paper
Ahs2208:Soil Science Ii
Course:Bachelor Of Horticulture
Institution: Meru University Of Science And Technology question papers
Exam Year:2012
QUESTION ONE – 30 MARKS
(a) Explain briefly how soil organic matter (Humus) influences the following soil properties. (i) Soil structure (ii) Soil water holding capacity (iii) Cation Exchange Capacity (iv) Soil colour (4Marks) (b) With the use of the Molecular Structural illustration, explain the following components of silicate clay: (i) Tetrahedral sheet (ii) Octahedral sheet (iii) Trioctahedral sheet (iv) Dioctahedral sheet (8Marks) (c) Explain the characteristics of the 1:1 and 2:1 type’s silicate clays and in each case give two examples. (7Marks) (d) Explain why the Chlorite and Kaolinite do not swell or shrink when wetted and dried as much as smectites. (7Marks) (e) What do you understand by: (i) Cation exchange (ii) Cation exchange capacity
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(iii) PH dependant charge (iv) Base saturation percentage.
QUESTION TWO – 20 MARKS
(a) Explain the sources of Hydron ions or soil acidity in the soil. (14Marks) (b) Explain the beneficial effects of soil organism. (6Marks)
QUESTION THREE – 20 MARKS
(a) Describe Aluminium toxicity in plants. (10Marks) (b) Explain the role of Aluminium in soil Acidity. (10Marks)
QUESTION FOUR – 20 MARKS
(a) Explain four mechanisms of Buffering of PH in soils. (10Marks) (b) Soil PH is measured in either (i) Soil paste or soil – solution suspension (ii) Soil – water or soil –salt suspension
Discuss each of the paired methods, highlighting the advantages, disadvantages and comparative PH value you would expect. (10Marks)
QUESTION FIVE – 20 MARKS
(a) In the laboratory determination of organic carbon, what is the role of the following: (i) Ammonium dichromate, concentrated sulphuric and phosphoric acid during digestion. (ii) Ferrous Sulphate during titration. (6Marks) (b) Describe the soil colloidal complex, indicate its various components and explain how it tends to serve as a ‘bank’ for plant nutrients. (14Marks)
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