Irrigation Requirement and Factors that affect Irrigation Requirement in very easy Language

Hello Friends! Welcome to our agricultural Blog again, in this Blog (article), we can try to understand the topic about Irrigation requirement and those Factors that affect Irrigation requirement. Why we require Irrigation?

Introduction about Irrigation Requirement

The Quantity of required or needed  water that must be supply to crops or Plants for their better growth and development during the growing season of crops.

Field Irrigation requirement of crop means water requirement of crops exclusive of effective rainfall and contribution from soil moisture. It may be given below-

IR = WR – (ER + S)

Factors affecting Irrigation requirement-

Some Factors that affect Irrigation water Requirement or Irrigation water requirement depends upon some factors, that are-

  1. Nature of crops
  2. Rainfall
  3. Nature of soil where crop may grow


  1. Nature of Crops-

Each Plant and crop require specific amount of water during their growth and stages, some crop require large amount of water for their growth and development while some crop requires less amount of water for their growth.

  1. Rainfall

Frequency of Irrigation also depends upon Rainfall just like other Factors such as Crop’s Nature and soil’s Nature.

Relations between Rainfall and Irrigation water requirement = both are Inversely Proportional to each other.

  1. Nature of soil where crop may grow-

There are many types of soil in our country India; Such as- Sandy soil, loam soil, clayey soil and sandy loam soil, etc. And those crops that are grow in sandy soil they require more Irrigation water while the crops that grow in clayey soil require less Irrigation water than loam soil and Sandy soil.


Net Irrigation Requirement

NIWR = Net Irrigation Water Requirement

Formulae of Net Irrigation Requirement are given below-

Formulae of Net Irrigation Requirement


  • d = Net Irrigation water to be applied (cm)
  • Mfci = Field capacity in ith layer (%)
  • Mbi = Moisture content before irrigation in ith layer (%)
  • Ai = Bulk density (g/cc)
  • Di = depth (cm)
  • N = no. of soil layer

Gross Irrigation requirement-

The total Quantity of water that is used for irrigation is known as Gross irrigation requirement.

Gross Irrigation = (Net Irrigation requirement/Field efficiency of system)  X 100

Gross Irrigation requirement can be determined for-

  1. For a Field,
  2. For a Farm,
  3. For an outlet command area,
  4. For an Irrigation Project,
  5. For various stages of crops.


Q. Why we calculated the Gross Irrigation requirement?


Irrigation Frequency-

Irrigation frequency is the day interval between two consecutive irrigation during crop period.


Design Frequency (days)

Formula = (FC – moisture content of the root zone) / Peak period consumptive use rate of crop


Irrigation Period-

Irrigation period is the number of days in which we supply the required water to our crops and Plants.

  • Irrigation Period = (Net amount of moisture in soil at start of Irrigation) / (Peak Period consumptive use of crop)


Effective rainfall-

Factors affecting Irrigation requirement

Effective Rainfall can be defined as the difference between Total rainfall and actual evapo tranpiration as given as Formulae-

  • ER = (Total Rainfall – ET)

Effective rainfall can be defined as the rainfall that is stored in root zone of crops and can be utilized by crops.


Evapo transpiration-

Irrigation Requirement

Evapo transpiration is the sum of Evaporation Process and Transpiration as written as below-

  • ET = E + T

Evapo transpiration is aso defined as the addition of Plants Transpiration through their vegetative parts and Evaporation from the surface of earth.


Potential Evapo transpiration-

The Potential or capacity of atmosphere to perform evapo transpiration from soil or field surface and from vegetative parts of Plants such as leaves, stems, etc.


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It is Arpan Priy Das from west champaran, Bihar. Arpan started his blog about agricultural information named as “ECOHILLAGRI.COM ” He started his blog to help many agricultural or other students as well as farmers. so, it is necessary for them to learn about agriculture that is useful for students as well as farmers and that all concepts are present in this blog.

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