Elements of Soil Science - Past Questions - 2065 Ashadh

Elements of Soil Science - Past / old Questions - 2065 Ashadh, Bachelor in Agricultural Engineering, Tribhuvan University, Nepal, Third semester

 

TRIBHUVAN UNIVERSITY
INSTITUTE OF ENGINEERING
Examination Control Division
2065 Ashadh

Exam: Back
Level: BE
Programme: B. Agri.
Year / Part: II / I
Subject: Elements of Soil Science
Full Marks: 80
Pass Marks: 32
Time: 3 hrs.

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✓ Candidates are required to give their answers in their own words as far as practicable.
✓ Attempt any Five questions.
✓ The figures in the margin indicate Full Marks.
✓ Assume suitable data if necessary.

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1.
a) What are different kinds of soil-forming factors? Describe in brief about these factors. [2+6]
b) Describe different horizons of soil profile with their characteristics. [8]

2.
a) What is soil water potential? How is water retained in soil? Explain the general pattern of moisture extraction from the root zone of plants. [2+3+3]
b) How can soil aeration in the field be assessed? What measures do you take to control soil temperature? [4+4]

3.
a) What are different types of plant nutrients? How does a plant respond to nitrogen deficiency? What are the different forms of nitrogen available in the soil? [3+2+3]
b) What is soil pH? Why does pH decrease when nutrients are absorbed? What do you mean by buffering of soils? Explain. [1+2+5]

4.
a) Explain the cation and anion phenomenon of soil colloids. [8]
b) What are the characteristics of taxonomical classification of soil? How is soil classified? [2+6]

5.
a) Following observations were found in gravimetric determination of soil moisture at successive depths of 15 cm in the root zone. Calculate the moisture content in equivalent depth of water in the root zone. [7]

Depth of soil layer in the root zone (cm)	Moist weight of soil (g)	Over-dried weight of soil (g)	Bulk density (g/cm³)
0-15	13	10	1.5
15-30	15	10	1.6
30-45	20	10	1.6
45-60	16	10	1.5

b) A soil sample has a particle density of 2.65 g/cm³ and bulk density of 1.8 g/cm³. Find the porosity of the soil. [1]
c) Differentiate soil texture and soil structure. Discuss the significance of soil texture in agriculture and soil management practices. [3+5]

6.
Write short notes on (any four): [4 × 4]
a) Triangular textural diagram
b) Soil survey
c) Controlling soil acidity
d) Indirect method of moisture measurement
e) Soil consistenc