Water Requirement of Crops MCQ Quiz in मल्याळम - Objective Question with Answer for Water Requirement of Crops - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

Explanation:

For Kharif: 

The culturable command area = 3554.4 hectares

Duty at the head of the canal = 1900 hectare per cumec

Discharge required(Q₁) = \(\frac{{{\rm{Culturable \ command\ area}}}}{{{\rm{Duty}}}}\)

Discharge required(Q1) = \(\frac{{{\rm{3554.4}}}}{{{\rm{1900}}}}\)

Discharge required(Q1) = 1.87 cumec

For Rabi: 

The culturable command area = 2369.9 hectares

Duty at the head of the canal = 2150 hectare per cumec

Discharge required(Q2) = \(\frac{{{\rm{Culturable \ command\ area}}}}{{{\rm{Duty}}}}\)

Discharge required(Q2) = \(\frac{{{\rm{2369.9}}}}{{{\rm{2150}}}}\)

Discharge required(Q2) = 1.10 cumec

Average discharge required(Q_av):

\({{\rm{Q}}_{{\rm{av}}}} = \frac{{{{\rm{Q}}_1} + {{\rm{Q}}_2}}}{2}\)

\(​​{{\rm{Q}}_{{\rm{av}}}} = \frac{{{{\rm{1.87}}\ } + {{\rm{\ 1.10}}}}}{2}\)

Q_av = 1.485 cumec = 1.49 cumec.

Duty:

The duty means the area of land that can be irrigated with the unit volume of irrigation water or it is the area of land expressed in hectare that can be irrigated with unit discharge i.e. 1 m3/s flowing throughout the base period, expressed in days. It is expressed as ha/m3/s or ha/cumec.

∴ \(\text{Duty}=\frac{\text{Area}}{\text{Discharge}}\)

From above it can be concluded that

1. Duty is more for more area if discharge is constant.

2. Duty is less if discharge is more for a given area.

Note:

Mathematically, Duty is given as:

\(D = \frac{{8.64B}}{{\rm{\Delta }}}\)

Where, D = Duty (in ha/m3/s), B = Base period (in days), Δ = Amount of water required by plant (in m)

Calculation:

Delta, \(\Delta ~=\frac{2\times 400\times {{10}^{6}}}{40000\times {{10}^{4}}}=2~m\)

Duty in hectares / cumec, \(D = \frac{{8.64\times125}}{{\rm{2 }}} = 540\; ha/cumec\)

Explanation

SAR 

Sodium-ion in small amounts is good for plants. But excess sodium ion creates a problem for both plant and soil. Excess sodium contributes to salinity and it is toxic for some sensitive crops.

Soil with high sodium content becomes very plastic in nature in the wet stage, which shows low permeability and poor aeration.

This excessiveness of sodium ion is measured in terms of sodium absorption ratio (SAR).

\({\rm{SAR}} = \frac{{\left[ {{\rm{N}}{{\rm{a}}^ + }} \right]}}{{\sqrt {\frac{{\left[ {{\rm{C}}{{\rm{a}}^{2 + }}} \right] + \left[ {{\rm{M}}{{\rm{g}}^{2 + }}} \right]}}{2}} }}\)

Where,

[Na+] = concentration of sodium ion in milli-equivalent per liter

[Ca2+] = concentration of calcium ion in milli-equivalent per liter

[Mg2+] = concentration of magnesium ion in milli-equivalent per liter

The correct answer is <2000 ha.

Explanation

Areawise division of Irrigation Projects:

• In the financial year 1978-79, Planning Commission classified the irrigation projects on the basis of Cultural Command Area (CCA) as follows:
  • Major Irrigation Projects - Project covering >10,000 ha of catchment command area.
  • Medium Irrigation Project - 2,000 to 10,000 ha of catchment command area.
  • Minor Irrigation Project - Less than 2,000 ha of catchment command area.
• Other than this, irrigation projects can also be classified on the basis of the type of flow:
  • Gravity Irrigation: In this type of project water is stored at height gravity makes it flow down to the required destination.
  • Lift Irrigation: In this type of project water is made to flow against gravity from a lower level to some height with the help of some external means.

Explanation

Zone of Rock Fracture is further divided into two zones:

1. Zone of Aeration 
2. Zone of Saturation

Zone of Aeration is further divided into three zones:

1. Root soil water zone
2. Intermediate zone
3. Capillary water zone

It is clear from the image that Ground Water comes under the Zone of Saturation.

Hence, In an underground profile, the zone of aeration does not include Groundwater

Calculation:

Given,

60 % of area during Kharif remained without water

i.e. Area got irrigated during Kharif = (100 – 60) % = 40 % 

Area during Rabi remained without water = 46 %

i.e.  Area got irrigated during Rabi = (100 – 46) % = 54 % 

∴ Intensity of Irrigation (I.O.I) is the area of land irrigated

∴ I.O.I = 40% + 54 % = 94 %

Concept:

1. Water Application efficiency

η_a = (W_s/W_f) × 100

Where W_s = Water Stored in root zone

W_f  = Water delivered to the field

2. Water Conveyance efficiency

η_c = (W_f/W_r) × 100

Where W_f = Water delivered to the field

W_f  = Water delivered from the reservoir (it includes losses from canals in form of seepage, evaporation etc.

3. Water Use efficiency

η_u = (W_u/W_f) × 100

Where W_u = Consumptive use of water

W_f  = Water delivered to the field

4. Water storage efficiency

η_s = (W_s/W_fc) × 100

Where W_s’ = Actual water Stored in root zone

W_fc = Water needed to be stored to bring the water content up to the field capacity.

Calculation:

Water stored in the root zone = 30 cm

Area of field = 40 hectares = 400000 m²

Water supplied = 8 cumecs

Duration = 6 hours

Volume of water supplied = 8 × 6 × 3600 = 172800 m³

Water supplied (in cm) = (172800/400000) × 100 = 43.2 cm

η_a = (W_s/W_f) × 100

Concept: 

The depth of water stored (dw) in the root zone is given by.

 \({d_w} = \frac{{{\gamma _d}}}{{{\gamma _w}}} \times d\left( {FC - PWP} \right)\)

where,

γd = dry unit weight of soil

γw = unit weight of water

d = depth of the root zone

PWP = Permanent wilting point

 FC - Field capacity

Calculation:

Given

 FC = 30 %, PWP = 10%

γd = 1.5 g/cc, γw = 1 g/cc

d = 1 m

The depth of water stored (dw) in the root zone

\(\therefore {d_w} = \frac{{1.5}}{{1}} \times 1 \times \left( {0.30 - 0.10} \right)\)

dw = 0.3 m = 300 mm

Explanation:

(i) The vadose zone is the undersaturated portion of the subsurface that lies above the groundwater table. The soil and rock in the vadose zone are not fully saturated with water; that is, the pores within them contain air as well as water.

Important point:

Phreatic zone or Saturated Zone:

The phreatic zone or zone of saturation, is the part of an aquifer, below the water table, in which relatively all pores and fractures are saturated with water. Above the water table is the vadose zone. The phreatic zone size, color, and depth may fluctuate with changes of season, and during wet and dry periods.

Explanation:

Tile drainage is a type of drainage system that removes excess water from soil below the surface. Plants need air as well as moisture in their root zones for their survival, excess irrigation farm water is free to move into the underground tile drains, this water if not removed retards the plant growth because It fills the soil voids and restricts proper aeration, Therefore there is a need for Sub-surface drainage or tile drainage.

Advantages of tile drainage for a farm are:

1. Increases the volume of soil from which the roots can obtain food
2. Removes the free gravity water that is not directly available to the plants
3. Increases air circulation.
4. Increases bacterial activity in the soil.
5. More consistent yields
6. Allows for more efficient use of resources
7. Reduces financial risk
8. Earlier and more timely planting
9. Improved harvesting conditions
10. Less wear and tear on equipment
11. Less power required for field operations
12. Better plant stand
13. Less plant stress
14. Fewer plant diseases
15. Less soil compaction