1. Which of the following statement is wrong about consumptive use coefficient?
a) It is different for different crops
b) It varies with the crop growth
c) It is different for the same crop at different places
d) It is independent of the crop type and its growth
Explanation: Consumptive use coefficient (k) = evapotranspiration (Cu or Et) / pan evaporation (Ep). It is different for different crops, varies with crop growth and is different at different crop stages for the same crop
2. What is the range of reflection coefficient for close-grained crops?
a) 0.15-0.25
b) 0.05-0.45
c) 0.05
d) 0.45-0.90
Explanation: The range of reflection coefficient for different surfaces are-
| Close-grained crops | 0.15-0.25 |
| Bare lands | 0.05-0.45 |
| Water surface | 0.05 |
| Snow | 0.45-0.90 |
3. Which method is widely used in India for the computation of consumptive use?
a) Penman’s equation
b) Hargreaves – Christiansen equation
c) Blaney-Criddle equation
d) Tanks and lysimeter
Explanation: The value obtained from Penman’s equation is almost equal to the values obtained from the actual field observations made in pan evaporation method. The values obtained from the Blaney-Criddle equation were on the much higher side (about 30%) and the values obtained from the Hargreaves method is on the lower side (about 15%-20%). Lysimeter method is time-consuming and expensive.
4. The average value of Et/Ep for citrus crops?
a) 0.90
b) 0.7-1.10
c) 0.60
d) 0.66-1
Explanation: Et/Ep ratio is consumptive use coefficient (k). Group F includes citrus fruits like oranges, grapefruit, etc. the Et/Ep ratio is fairly constant throughout the year and average to a value of about 0.60.
5. The monthly consumptive use is given by ___________
a) Cu = k.p/40 [1.8t + 32]
b) Cu = k.p/40 [1.8t – 32]
c) Cu = k.p/40 [t + 32]
d) Cu = k.p/40 [t – 32]
Explanation: BLaney – Criddle formula is used to calculate monthly consumptive use.
Cu = k.p/40 [1.8t + 32] Where, Cu is monthly consumptive use in cm, K = crop factor, T = mean monthly temperature in °C, and P = monthly % of annual day light hours that occur during the period.
6. Which zone is the most important from an irrigation point of view?
a) Soil Zone
b) Intermediate Zone
c) Capillary Zone
d) Saturation Zone
Explanation: From this soil zone plants take their water requirements which are needed during their growth. As in this zone roots of the plants are present.
7. What is the name of water which flows under gravity?
a) Hygroscopic Water
b) Gravity Water
c) Capillary Water
d) Residue Water
Explanation: When water flows over the land, some water is absorbed in the root zone and remaining water flows underground due to the action of gravity, hence the name gravity water
8. Field capacity is different from gravity water.
a) True
b) False
Explanation: Immediately after application of irrigation water or sudden rain the gravity water drains down to the water table. But certain amount of water gets retained on the surfaces of soil grains and this water cannot be easily drained under action of gravity. This water is called field capacity.
9. How many days are generally taken to obtain field capacity after free gravity drainage?
a) 3 to 7 days
b) 4 to 8 days
c) 5 to 9 days
d) 2 to 5 days
Explanation: Generally field capacity is defined as the water content of soil that is left after free gravity drainage for certain period of time. This period of free gravity drainage is generally taken as 2 to 5 days.
10. By what type of forces the soil grains retain water on their surfaces?
a) Capillary Forces
b) Cohesive Forces
c) Molecular Attraction and by Loose Chemical Bonds
d) Compressive Forces
Explanation: Due to these forces like molecular attraction between adjacent soil grains and by their loose chemical bonds, i.e adsorption, the soil grains are able to retain water against the action of gravity on their surfaces.