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Aae 2102: Soil Science Question Paper

Aae 2102: Soil Science

Course:Bachelor Of Science In Agricultural Engineering

Institution: Jomo Kenyatta University Of Agriculture And Technology question papers

Exam Year:2012

JOMO KENYATTA UNIVERSITY
OF
AGRICULTURE AND TECHNOLOGY

University Examinations 2012/2013
FIRST YEAR EXAMINATION FOR THE DEGREE OF BACHELOR SCIENCE IN AGRICULTURAL ENGINEERING

AAE 2102: SOIL SCIENCE

DATE: AUGUST, 2012 TIME: 2 HOURS

INSTRUCTIONS: Answer Question ONE and Any Other TWO Questions.

Question One

a) i. Name and briefly describe the major soil horizons. [5 marks]

ii. Use the data given to calculate; gravimetric water content, bulk density and porosity of the soil sample.

Soil property Value

Weight of sample in air 180.0g
Weight of sample in water 50.23g
Oven dry weight 170.0g
Particle density 2.63g/cm3

b) A soil sample has the following cations on the exchange complex: H+(13 meq/kg soil), Na+ (7meq/kg soil), ca2+ (26meq/kg soil),K+ (12meq/kg soil), and Mg2+ (19meq/kg soil).

i. What is the total CEC of the soil? [2 marks]
ii. How many meq of Na are on 1kg of soil? [2 marks]
iii. How many meq of Ca are required to replace all the Na on the soil exchange
complex? [3 marks]

c) Why is Potassium important in plant nutrition? [4 marks]

d) Explain briefly the components and distribution of an ideal mineral soil. [8 marks]

Question Two

Define the following terms:

a) Saturation
b) Field capacity
c) Wilting point
d) Hygroscopic water
e) Plant available water [5 marks]

b) i. Explain in detail the factors that affect soil water. [10 marks]

ii. Explain briefly how the following methods are used to measure soil moisture content.

I. Gravimetric [2 marks]
II. Neutron probe [3 marks]

Question Three

a) Explain in details the five basic structural units. [10 marks]

b) i. Differentiate between active and potential acidity. [2 marks]

ii. What are the causes of soil acidity? [5 marks]

c) What are the factors which affect soil micro-organism population? [3 marks]

Question Four

a) Describe in details using a well labeled sketch, the nitrogen cycle. [10 marks]

b) Explain in details the major factor one would consider when choosing a fertilizer for use in his/her farm. [6 marks]

c) Explain briefly the main reasons why liming is carried out. [4 marks]

Question Five

Discuss in detail the factors which affect the formation of soil. [20 marks]

Aae 2102: Soil Science Question Paper

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