Classes of Soil Water and Different Soil Moisture Levels

Q. Calculate the permanent wilting point if the depth of water in the root zone at the permanent wilting point per meter depth of soil is 0.4m. The dry density of the soil is 16 KN/m³.

1. 0.025
2. 0.245
3. 0.4
4. 0.64

Q.

The moisture content of the soil in the root zone of an agricultural crop at a certain stage is found to be $0.05$. The field capacity of the soil is $0.15$. The root zone depth is $1.2m$. The consumptive use of crops at this stage is $3mm/day$ and there is no precipitation during this period. Irrigation efficiency is $65\%$. It is intended to raise the moisture content to the field capacity in $8$ days through irrigation. The necessary depth of irrigation required is__

1. 284 mm
2. 314 mm
3. 406 mm
4. 456 mm

Q. The state of the soil when plants fail to extract sufficient water for their requirements is____.

1. Maximum saturated point
2. Permanent wilting point
3. Ultimate utilization point
4. None of these

Q. The field capacity of a certain soil is 20% and the moisture content of the soil before irrigation is 10%. What is the approximate depth upto which the soil will be wetted with an application of 50 mm of water?
[Take dry unit weight of soil as $15kN/m^3$ and unit weight of water as $10kN/m^3$]

1. 250 mm
2. 333 mm
3. 367 mm
4. 433 mm

Q. The soil moisture tension of soil at permanent wilting point ranges from:

1. 0 - 5 atm
2. 5 - 30 atm
3. 30 - 45 atm
4. > 45 atm

Q. For an irrigated field having: Field capacity = 30%, Permanent wilting point = 10%, Permissible depletion of available moisture = 40%, Dry weight of soil = 14.70 kN/m${}^3$, Unit weight of water = 9.8 kN/m${}^3$ and Effective rainfall = 30 mm, what is the net irrigation requirement per meter depth of soil?

1. 300 mm
2. 150 mm
3. 120 mm
4. 90 mm

Q. Consider the following zones :

1. Saturation zone
2. Capillary zone
3. Intermediate zone
4. Soil water zone

Which of these does not relate to the zone of aeration in the soil profile?

1. 1 and 2
2. 2 and 3
3. 4 only
4. 1 only

Q. The field capacity of a certain soil is $15\%$ and the moisture content of the soil before irrigation is $8\%$. If the dry unit weight of soil is $15.3kN/m^3$, the depth upto which the soil profile will be wetted with an application of $60mm$ of water is ________ mm.

1. 549.58

Q. The following data were noted from an irrigation field:

1. Field capacity = 20%
2. Permanent wilting point = 10%
3. Permissible depletion of available soil moisture = 50%
4. Dry unit weight of soil $=15kN/m^3$
5. Effective rainfall = 50 mm

The net irrigation requirement per meter depth of soil will be

1. 75 mm
2. 125 mm
3. 50 mm
4. 25 mm

Q. The water utilization by plants is available in the form of:

1. Gravity water
2. Hydroscopic water
3. Capillary water
4. Chemical water

Q.

Consider the following statements in connection with the soil-water-crop relationship:

1. Water utilization by plants is mainly from capillary water.
2. The amount of irrigation water required to meet the evapotranspiration needs of the crop during its full growth duration is its consumptive irrigation requirement.
3. The depth of water required to bring the soil-moisture level of a given soil up to its field capacity is called hygroscopic water.
4. With the continuous increase in the quantity of water applied, the yield of most crops increases up to a certain limit and then is expected to be constant.

Which of the above statements are correct?

1. 1 and 2
2. 2 and 3
3. 3 and 4
4. 1 and 4

Q.

Farmers use water for………………