This document discusses irrigation and crop water requirements. It outlines several advantages of irrigation including preventing disease and weeds, enabling cash crops, improving groundwater storage, and increasing crop yields. Some disadvantages are excessive water leakage causing marshes, waterlogging from high water tables, lower temperatures, and land/water pollution. Crop water requirement depends on factors like crop type, growth stage, soil properties, climate, and agronomic practices. It is the total water needed from sowing to harvest and includes transpiration, evaporation, and water for plant metabolism. The factors affecting consumptive water use by crops are also summarized.

1. Welcome Civil Engineers

2. IRRIGATION
Advantages
1. Prevents Disease and Weeds
 2. Irrigation makes it possible to
grow cash crops which give good
returns to the cultivators. Examples
of cash crops are; sugarcane, potato,
tobacco etc.
 3. It improves the groundwater
storage as water lost due to seepage
adds to groundwater storage.
 4. It improves the yields of crops
which mean more income for the
farmer people prosperous.
 5. We use it to help the growth of
crops during the period of
inadequate rainfall.
Dis-advantages
1. Excessive seepage and leakage of water
forms marshes and ponds all along the
channels.
2. Excessive seepage into the ground
raises the water-table and this in turn
completely saturates the crop root-zone.
It causes waterlogging of that area.
3. It lowers the temperature and makes
the locality damp due to the presence of
irrigation water.
4. Under irrigation canal system
valuable residential and industrial land
is lost.
5. Leads to unhealthy climate and
Makes soil and ground water pollution.

3. The total amount of water needed by a crop from the
time of its sowing upto the period of harvesting .
Or
The total amount of water needed to meet the water
loss through Evapo-transpiration.
This Quantity of Water required by crop varies
from crop to crop and sowing-harvesting period
depending upon the capacity of soil
To retain water.
Crop water requirement is the water required by
the plants for its survival, growth, development
and to produce economic parts.
Overall the total water requirement of crop based on soil moisture condition

4. The following features which mainly influence
the crop water requirement are:
1) Crop factors
a) Variety
b) Growth stages
c) Duration
d) Plant population
e) Crop growing season
2) Soil factors
a) Structure
b) Texture
c) Depth
d) Topography
e) Soil chemical
composition.
3) Climatic factors
a) Temperature
b) Sunshine hours
c) Relative humidity
d) Wind velocity
e) Rainfall
4) Agronomic
management factors
a) Irrigation methods used,
b) Frequency of irrigation
and its efficiency
c) Tillage and other cultural
operations like weeding,
mulching etc

5. Crop Water Requirement includes all losses like:
a) Transpiration loss through leaves (T)
b) Evaporation loss through soil surface in cropped area (E)
c) Amount of weather used by plants (WP) for its metabolsm These
three components cannot be separated so easily.
Hence the ET loss is taken as crop water use or crop water
consumptive use.
d) Other application losses are conveyance loss, percolation loss,
runoff loss, etc., (WL).
e) The water required for special purposes (WSP) like puddling
operation, ploughing operation, land preparation, leaching,
requirement, for the purpose of weeding, for dissolving fertilizer and
chemical, etc.
Thecropwaterrequirementvariesfromplaceto place,fromcrop to crop
anddependsonagro-ecologicalvariationandcropcharacters.

6. Consumptive Use Of
Water
Quantity of water require by plant to meet to meet it’s
evaporation-transpiration & to meet metabolic activities
.
C.U = E +T + 𝑊𝑚
>99% <1%
~ E+T C.U =consumptive use
𝑊𝑚 =Water require for
metabolic process
E = Evaporation
T =Transpiration

8. 1 . CLIMATIC FACTOR :
a) Radiation
b) Temperature
c) Humidity
d) Wind velocity
e) Rainfall
2. CROP FACTOR:
a) No. & size of stomata
b) Opening & closing of
stomata
c) Plant architecture & planting
pattern
d) Stages of growth
e) Rooting depth & pattern
f) Duration of the crop
3. SOIL FACTOR:
a) Water holding capacity
b) Infiltration rate
c) Soil water depth
4. MANAGEMENT FACTOR:
a) Time of sowing
b) Mulching
c) Fertilizer application
Factor affecting Consumptive use
of Water

9. Smarty