Agronomy module - Agrometeorology 1

Introduction

Agrometeorology is a science investigating the meteorologic, climatologic and hydrologic conditions which are significant for agriculture owing to their interaction with the objects and processes of agricultural production.

            A science dealing with climatological conditions which have direct relation or relevance to agriculture.

            Growth, development and productivity of plants depend on several factors.  These factors can be broadly divided into two major groups viz., internal factors (Genetic or hereditary) and external or environmental (surrounding) factors.  The environmental factors are

            i)          Climate (Meteorological elements)

            ii)         Edaphic (Soil)  

            iii)        Biotic (living organisms)

            iv)        Physiographic (elevation)

            v)         Anthrophic (man)

            This course on agrometeorology deals with the behaviour of the weather elements and their effect on crop production.

Climate: The aggregate of weather conditions over a longer period of time

Weather: The state of the atmosphere with respect to wind, temperature, cloudiness, relative humidity, pressure etc., at given time and at a given time.

Agroclimatic regions:  The grouping of different physical areas within the country into broadly homogeneous zones based on climatic and edaphic factors.

• The word “Meteorology” is of Greek origin, meaning, discourse  or study on things about and included meteors and optical phenomena. 
• An international Meteorological Organisation had been established in 1878. 
• The world meteorological organisation (WMO) took its present form in 1951.  It serves as a specialized agency to carryout the world wide exchange of meteorological informations with the head quarters in Geneva, Switzerland.
• The India Meteorological Department (IMD) was established in the year 1875.  The division of Agricultural Meteorology was started by the IMD in 1932 to meet the needs of agriculturist and researchers. 

Composition of Atmosphere

Constituent	Percent by volume
Nitrogen (N2)	78.08
Oxygen (O2)	20.94
* Argon (Ar)	0.93
Carbon dioxide (Co2)	0.03
* Neon (Ne)	0.0018
* Helium (He)	0.0005
Ozone (O3)	0.00006
Hydrogen (H2)	0.00005
* Krypton (Kr)	Trace
* Xenon (Xe)	Trace
Methane (Me)	Trace

·         Inert chemically never found in any chemical compounds.

• The maximum concentration of Ozone are found between about 30 and 60 km. 
• The water vapour content of air may vary from 0.02 per cent by volume in a cold dry climate to nearly 4 per cent in the humid tropics. 

Troposphere:

• It contains about 75 per cent of the total gaseous mass of the atmosphere.
• Under normal conditions, the height of the troposphere at the poles is about 8 kilometers, while at the equator it is about 18 kilometers.  

Stratosphere:

• The stratosphere begins at the troposphere which forms its lower boundary.  The lower stratosphere is isothermal in character 18 to 50 kilometers. 
• Presence of ozone layer is a special feature of this structure.

Mesosphere:

• Mesosphere exist from the height of 50 to 80 Km from the surface of the earth
• In this layer the temperature increases with height @ 5^oC/km.

Ionosphere:

• Above Mesosphere, the temperature fulls again reaching a minimum of about 100^oC at a height of 80 km.

Exosphere:  

• The outer most layer of earth's atmosphere is known as the exosphere which lies between 400 and 1000 kilometers.

Latitude:  Angular distance, measure in degrees, north or south from the equator.

Equator: An imaginary circle around the earth, equally distant at all points from both the North pole and the south pole. 

Longitude: (Length) Distance east or west on the earth's surface measured as an are of the equator (in degrees upto 189^o or by the difference in time) between the meridian passing through a particular place and a standard or prime meridian, usually the one passing through Greenwich, England.

Meridian: A great circle of the earth passing through the geographical poles an any given point on the earth's surface. 

Weather elements

1.      Solar radiation.

2.      Temperature, Air pressure

3.      Wind velocity and wind direction

4.      Moisture (humidity)

5.      Cloudines (Sunshine hours)

6.      Precipitation (Rainfall)

The  crop region are classified on the basis of average rainfall which are as follows:

                                   

Rainfall (mm)	Name of the climatic region
Less than 500	Arid
500 – 750	Semi Arid
750 – 1000	Sub humid
More than 1000	Humid