Soil Moisture and their 2 methods to measure in very easy language

Introduction about Soil Moisture and their measurement

Soil Moisture-

Soil Moisture is the water that is available or held or retained in the pores of soil.

Measurement of soil moisture-

Soil Moisture can be measured with two methods-

  1. Direct Methods
  2. Indirect Methods

 

Direct Method to measure the Soil moisture-

Direct Method involves the determination of Property of water in the soil. Some suitable methods that include in direct methods which help to determine the soil moisture. That are-

  1. Gravimetric Method

  2. Using Methyl alcohol

  3. Volumetric method

Gravimetric methods are also of four types-

  1. Physical Gravimetric method
  2. Thermogravimetry method
  3. Precipitative gravimetric analysis
  4. Electrode Position

Thermogravimetry method is also known as Oven drying method or, TGA.

 

  1. Indirect method to measure the Soil moisture-

Tensiometer- A device to measure soil moisture
Tensiometer

In Indirect method involves the determination of property of water in the soil. Some common  Instruments are included in indirect method, those are-

  1. Tensiometer

  2. Gypsum Block

  3. Neutron Prode

  4. Pressure Plate and Pressure membrane apparatus.

Measurement of moisture content-

  1. By Thermogravimetry OR, Oven drying method to determine moisture content-

Procedure-

  • Soil sample is collected.
  • Record the weight of that soil sample with moisture (called as Wet weight).
  • Dry that sample of collected soil at 105 degree Celsius in hot air oven until constant weight is obtained.
  • Record the weight of Dried soil (called as Dry weight).
  • Now, we can measure the moisture content in collected soil sample, This is on weight Basis measure.

Formulae of Moisture content of soil on weight Basis is-

Soil Moisture content = (wet weight-Dry weight)/Dry weight X 100

  1. Volumetric method to determine moisture content-

Procedure-

  • Soil sample is collected with tube auger whose volume is known.
  • Calculate the moisture content with Oven drying method.
  • Also calculate Bulk Density of Soil.
  • Then Calculate the volume of soil moisture content from the given formulae-

Formula-

Bulk Density of Soil= Weight of dry soil (in gram)/Volume of Dry Soil (in cm)

Volume of soil moisture content= moisture content by weight X Bulk Density of Soil

  • Moisture content by weight by Gravimetric method OR, oven drying method.
  • Bulk Density of Soil is obtained through above formulae.

 

Some important Numerical Question Based on Oven Drying method of measurement of moisture content in Soil-

  1. Mr, Shyam, a Soil Scientist want to measure the moisture content in the soil of his field. He collected some soil sample from his field, he dried that soil sample and weighted 10 gram. After dry that sample, He calculated the moisture content in his field that is 30 per cent. What is the weight of old soil sample?
  2. The moisture Percentage of a Black Soil is 40 and when weight of Black soil is recorded with moisture is 10 gram. Then what is the weight of Black soil sample after null moisture is remaining?

 

Answer-

1st Question:-

Moisture content = 30 per cent.

Dry weight of soil sample = 10 gram

Old Weight =?

Soil Moisture content = (wet weight-Dry weight)/Dry weight X 100

30 = (x – 10) / 10 X 100

30 = (x – 10) X 10

3 = x – 10

3 + 10 = x

X = 13 gram

Means, Weight of old Soil Sample = 13 gram.


 

2nd Question:-

Moisture Percentage = moisture content = 40 per cent

Wet weight of Black Soil = 10 gram

Null moisture = 0 per cent of moisture

Means soil is dried.

Dry weight of Black soil = ?

40 = (10 – x) / x X 100

4x = 100 – 10x

14x = 100

x = 100/14

x = 7.14


 

Water Requirement for Crops-

NOTE = Water Requirement for Crops is also known as Crop water requirement.

Soil moisture
Crop water requirement

Some important Abbreviations are given below-

  • ET = Evapo transpiration
  • PET = Potential Evapo transpiration
  • WR = Water requirement
  • WP = Water used by Plant
  • WL = Water Loss
  • WSP = Water required for Special Purpose
  • IR = Irrigation Requirement
  • ER = Effective Rainfall
  • T = Transpiration Loss
  • CU = Consumptive use
  • S = Soil moisture contribution

Introduction about Crop Water requirement-

Crop Water requirement is the Total water that is required by the crops and Plants for Proper growth and development of Plants and Crops, their Life and to produce vegetative Parts.

This water required for crop is supply with the help of two methods, that’s are-

  1. Naturally- Required water is supply through Rain (Precipitation)
  2. Artificially- Required water is supply through Irrigation.

Losses during crop water requirement-

Crop Water requirement is includes some losses, Such as-

  1. Transpiration Loss through leaf and vegetative Parts of Plants and Crops (denoted as T).
  2. Evaporation Loss through soil surface of field where crops are sown (denoted as E).
  3. Amount of water used by Plants for their metabolic and Enzymic activities (denoted as WP).
  4. Some other Water losses occur during Runoff Loss, Percolation loss (denoted as WL).
  5. Water required for special Purpose such as- Land Preparation, Leaching. Puddling, etc.

 

Symbolically, Water requirement is represented as-

  • WR = T + E + WP + WL+WSP
  • WR= IR+ER+S
  • WR= CU+WL+WSP

Where, CU = E+T+WP

 

Factors that affect crop water requirement-

The crop water requirement varies –

  1. From one Place to another Place.
  2. From crop to crop.
  3. From different agro ecological variation.

Some other important factors that also affect crop water requirement-

  1. Crop Factors
  2. Soil Factors
  3. Climatic Factors
  4. Agronomic management Factors.

 

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See Also


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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 ecohillagri.com 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.

3 thoughts on “Soil Moisture and their 2 methods to measure in very easy language

  • November 8, 2020 at 11:44 am
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    I suspect that you’re trying to avoid bad feeling with this post, but please remember that the more controversial opinions will lead to good dialogue when argued with respect..and this is your blog not a democracy- let your voice set the tone here!

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