ADVERTISEMENTS:
Here is a compilation of essays on ‘Solar Radiation’ for class 7, 8, 9 and 10. Find paragraphs, long and short essays on ‘Solar Radiation’ especially written for school students.
Essay on Solar Radiation
Essay Contents:
- Essay on the Meaning of Solar Radiation
- Essay on the Mechanism of Solar Radiation
- Essay on the Distribution of Solar Radiation
- Essay on the Energy Balance of Solar Radiation
- Essay on the Spectral Distribution of Solar Radiation
- Essay on the Factors Affecting the Distribution of Solar Radiation
- Essay on the Measurement of Solar Radiation
- Essay on the Effects of Solar Radiation
Essay # 1. Meaning of Solar Radiation:
ADVERTISEMENTS:
The earth receives heat energy from three basic sources viz. (i) solar radiation, (ii) gravity, and (iii) endogenetic forces coming from within the earth but the solar radiation is the most significant source of terrestrial heat energy. ‘The radiant energy received from the sun, transmitted in a form analogous to shortwaves (1/250 to 1/6700mm in length), and travelling at the rate of 1, 86,000 miles a second, is called solar radiation or insolation’ (G.T. Trewartha).
The sun is a great engine that drives winds on the earth’s surface, ocean currents, exogenetic or denudational processes and ultimately sustains life in the biosphere. Solar energy received from the sun through solar radiation heats the earth’s surface and the atmosphere and thus is responsible for the movement of air and currents through changes in pressure gradients, drives the hydrological cycle through evaporation and precipitation which in turn helps in the cycling and recycling of nutrients and chemical elements in the biosphere through the broader cyclic pathways collectively known as ‘geo-biochemical cycles’, helps the plants to prepare their food through the process of ‘photosynthesis’ which infact, changes solar energy into chemical energy which is used by plants, animals and man, through different trophic levels of food chains and food webs.
Essay # 2. Mechanism of Solar Radiation:
The source of energy of the sun is its interior wherein the hydrogen is converted into helium due to enormous confining pressure and very high temperature under the process of nuclear fusion which generates huge quantity of heat. This heat is transported to the outer surface of the sun through convection and conduction from below.
ADVERTISEMENTS:
It may be pointed out that the rate of generation of heat inside the sun is more or less constant and hence the radiation of energy from the outer surface of the sun (called as photosphere) is also more or less constant. Thus, the amount of solar radiation or the solar energy received on a unit area of the surface facing the sun at the average distance between the sun and the earth is also more or less constant and is called as solar constant.
Thus, it is obvious that the solar constant refers to the rate of radiation from the sun which is of the value of 2 gram calories per square centimetre per minute (2 cal/cm2/min). It is also expressed in terms of langley (a unit measure of heat energy, one gram calorie per square centimetre is equal to one langley) as 2 langley per minute.
There are two basic laws which govern the nature and flow of radiation as given below:
(1) Wien’s Displacement Law:
ADVERTISEMENTS:
Wien’s displacement law ‘states that the wavelength of the radiation is inversely proportional to the absolute temperature of the emitting body.’
(2) Stefan—Boltzmann Law States:
Stefan Boltzmann law states ‘that flow, or influx, of radiation is proportional to the fourth power of the absolute temperature of the radiating body.’
The surface temperature of the sun is 6000°C or 11000°F. The highly incandescent gas of the sun’s surface being heated from below emits bundle of energy called ‘photon’ which is infact the particle of radiation which has the property of wavelength. Continuous emission of photons from the sun’s surface causes continuous bands of radiation having certain wavelength which is considered as short wavelength in relation to the earth’s outgoing long-wave radiation.
The solar energy radiated from the outer surface of the sun in the form of electromagnetic wave is called as electromagnetic radiation, which travels at the speed of 3,00,000 km per second (1,86,000 miles per second). The solar energy received at the earth’s surface is called insolation or solar radiation.
The energy from the sun is emitted in the form of electromagnetic waves which travel outward in radial manner from the sun almost in straight line and take 8 minutes 20 seconds to reach the earth’s surface after covering an average distance of 150 million km (93 million miles) between the sun and the earth.
The electromagnetic radiation waves are expressed in terms of wavelengths (L). The straight distance between two successive crests or troughs is called wavelength (fig. 33.1) (L) which is expressed in the length units of metres, centimetres, millimeters, microns etc.
The number of radiation waves (one radiation wave is equal to one wavelength) passing through a certain point per unit time (usually one second) is called wave frequency which varies according to the wavelengths of the radiation waves. There is inverse relationship between the wavelength and wave frequency i.e., shorter the wavelength, higher the wave frequency and longer the wavelength, lower the wave frequency (fig. 33.1).
In other words, high wave frequency is associated with short wavelength and low wave frequency is associated with long wavelength. Wave frequency is generally expressed as wave cycles per second. The wave cycles are usually expressed by the unit of measure of hertz.
ADVERTISEMENTS:
For example, one hertz per second represents one wave cycle meaning thereby only one wave-length passes per second from a fixed point. Hertz is further expressed in kilohertz (1,000 hertz) or megahertz (1,000,000 hertz).
The electromagnetic radiation emitted from the outer surface of the sun consists of four spectra of radiation waves having different wavelengths and wave frequencies.
(1) The first spectrum of the electromagnetic waves includes gama rays, hard x-rays, soft x-rays and ulra violet rays The wavelengths of this spectrum of the shortest wavelengths are expressed in the unit measure of ‘angstrom’ wherein one angstrom is equal to 0.000,000.01 cm or 10-8 cm.
The following are the wavelengths of the waves of the spectrum of the shortest waves:
(2) The second spectrum of the electromagnetic radiation waves is also called as the spectrum of visible light or rays which includes violet, blue, green, yellow, orange and red rays which carry 41 per cent of the total energy of the solar spectrum of all the electromagnetic radiation waves. The unit of the measure of wavelengths of this spectrum is micron (one micron is equal to 0.0001 cm or 10,000 angstroms). The wave frequency of these different rays ranges between 109 and 108 megahertz per second.
The wavelengths of these visible rays are as given below:
(3) Third spectrum of the electromagnetic radiation waves is called as infrared spectrum which consists of infrared waves of the wavelengths ranging from 0.7 micron to 300 microns. The wave frequency ranges between 108 and 106 megahertz per second.
(4) Fourth spectrum of the electromagnetic radiation wave consists of long-waves including microwaves, radar waves and radio waves. The unit measure of these wavelengths of long-waves is usually centimetre to metre. The wavelengths of microwaves range between 0.03 cm and 1.0 cm.
These waves are used to send messages from one place to other distant places. The wavelengths of radar waves vary from 1.0 cm to 100 cm (1 m).
The radar system is divided into two subsystems on the basis of frequency viz.:
(i) Radio system, and
(ii) Television system.
The radar, television and radio waves are divided into 6 categories on the basis of wave frequency and wavelengths:
Essay # 3. Distribution of Solar Radiation:
On an average, the amount of solar radiation received at the earth’s surface decreases from equator towards the poles but there is temporal variation of insolation received at different latitudes at different times of the year.
Table 33.1 depicts the amount of insolation received at the outer boundary of the atmosphere and at the earth’s surface at the time of winter solstice (22 December), vernal equinox (21 March), summer solstice (21 June) and autumnal equinox (23 September) as given by Baur and Phillips.
It is apparent from table 33.1 that the amount of solar radiation reaching the outer limit of our atmosphere is significantly more at different latitudes (A in table 33.1) than the amount of insolation received at the ground surface. This trend reveals the fact that a sizeable portion of incoming solar radiation is lost while passing through the atmosphere due to cloudiness, atmospheric turbidity (scattering), reflection, and absorption (through ozone).
The data of insolation as portrayed in table 33.1 – A further reveal that maximum insolation reaches the outer limit of the atmosphere at north pole at the time of summer solstice while maximum insolation is received at the ground surface between latitudes 30°-40° N on 21st June because of minimum amount of cloudiness due to the presence of subtropical high pressure belt and anticyclonic conditions.
Table 33.2 reveals the fact that the total amount of insolation received at the earth’s surface decreases from equator towards the poles. The insolation becomes so low at the poles that they receive about 40 per cent of the amount received at the equator. The tropical zone extending between the tropics of Cancer (23.5° N) and Capricorn (23.5°S) receives maximum insolation.
Not only this, there is very little variation of insolation during winter and summer seasons because every place experiences overhead sun twice every year.
The globe is divided into 3 zones on the basis of the amount of insolation received during the course of a year:
(1) Low latitude or tropical zone extends between the tropics of Cancer and Capricorn. All places experience overhead sun (sun’s rays are vertical) twice during the course of a year due to northward and southward march of the sun. Consequently, every place receives maximum and minimum insolation twice a year. The region receives highest amount of insolation of all other zones and there is little seasonal variation.
(2) Middle latitude zone extends between 23.5° and 66° latitudes in both the hemispheres. Within this zone every place receives maximum (at the time of summer solstice – 21 June in the northern hemisphere and at the time of winter solstice – 22 December in the southern hemisphere) and minimum (at the time of vernal equinox – 21 March in the northern hemisphere and at the time of autumnal equinox – 23 September in the southern hemisphere) insolation once during the course of a year. Insolation is never absent at any time of the year but seasonal variation increases with increasing latitudes.
(3) Polar zone extends between 66° and 90° (poles) latitudes in both the hemispheres.
Every place receives maximum and minimum insolation once during the course of a year but sometimes insolation becomes zero due to absence of direct solar rays.
Essay # 4. Energy Balance of Solar Radiation:
Solar energy meets two important aspects of crop growth. Firstly, it influences the thermal environment for physiological functions of the crops. Secondly, it establishes satisfactory light environment for photosynthesis and other crop functions. For the process of transpiration, a growing crop requires energy at the rate of 590 cal g-1 of water evaporated. Almost all this energy must come from the sun.
Knowledge of energy balance is important in understanding the likely magnitude of evapotranspiration in a given environment and the extent to which the crops restrict transpiration. It is also useful in understanding photosynthetic efficiencies of crops. Energy balance of the earth’s surface can be expressed by an equation equating all incoming and outgoing energy flux densities.
Net rate of incoming energy per unit area = Net rate of outgoing energy per unit area.
Rs (1- ρ) = R1 + G + H + LE (cal cm-2 s-1)
where, Rs = flux density of total shortwave radiation received by the ground surface from the sun and sky.
ρ = albedo of ground surface.
R1 = net flux density of long-wave radiation emitted by the surface, the difference between that emitted and absorbed.
G = heat flux density into the ground.
H = sensible (non-latent) heat flux density into the atmosphere.
L = latent heat of vaporisation of water (cal g-1) and transpiration.
Energy balance for crop surface can be derived from the following equation:
Rs = (1-ρ) –R1, = P + G + A + LE (cal cm-2 s-1)
where, Rs = incoming total shortwave radiation energy from the sun and sky falling on the crop
ρ = albedo of crop surface such that Rs (1- e) is the amount of energy absorbed
R1 = net flux density of long wave radiation emitted by crop surface
P = radiant energy utilised during photosynthesis
G = heat flux density into ground
H = sensible heat flux density for warming up the air in contact with crop and soil
LE = heat flux density to evaporate water from crop and soil (latent heat).
Essay # 5. Spectral Distribution of Solar Radiation:
Total solar radiation is defined as the sum of direct and diffusive radiation received on a horizontal surface. The diffusive component is the short wave energy scattered downwards by the terrestrial atmosphere. Diffuse sky radiation is different from atmospheric radiation which is a long wave radiation with maximum value around 15 m.
The proportion of diffuse component depends on the latitude, elevation, altitude, sun’s inclination and atmospheric turbidity. The principal factor, however, is clouds. The proportion of diffusive radiation at Indian stations varies from 0.18 to 0.80. Radiation in the range of 0.39 to 0.79 m is the light which the human eye perceives.
All the colours from violet to red make up the visible spectrum. At earth surface, visible wavelengths represent about 50 to 60 per cent of total solar radiation.
Essay # 6. Factors Affecting the Distribution of Solar Radiation:
It is apparent from the foregoing discussion that the amount of insolation received at the earth’s surface varies significantly (decreases) from equator towards the poles due to certain astronomical and geographical factors viz.:
(i) Angle of the sun’s rays,
(ii) Length of day,
(iii) Distance between the sun and the earth,
(iv) Sunspots and
(v) Effects of the atmosphere.
(1) Angle of the Sun’s Rays:
The angle between the rays of the sun and the tangent to the surface of the earth at a given place largely determines the amount of insolation to be received at that place. The sun’s rays are more or less vertical (maximum angle of 90° between the sun’s rays and the tangent to the earth’s surface) at the equator and become more and more oblique poleward.
In other words, the angle of the sun’s rays decreases poleward. As per rule vertical rays bring more insolation than oblique rays. In other words, as the angle of sun’s rays decreases poleward, the amount of insolation received also decreases in that direction.
The control of the angle of the sun’s rays on the amount of insolation may be explained with the following examples:
(i) Vertical rays are spread over minimum area of the earth’s surface and they heat the minimum possible area and thus the energy received per unit area increases. On the other hand, oblique rays are spread over larger area of the earth’s surface and hence the amount of energy received per unit area decreases.
It is, obvious from fig. 33.2 that A and B bands of the sun’s rays are of uniform width and carry equal amount of solar energy but the area (S) covered by A band is much smaller than the area covered by B band (O) and therefore the amount of insolation received per unit area over S surface is greater than over O surface area (fig. 33.2).
(ii) Oblique rays have to pass through thicker portion of the atmosphere than the vertical rays. Thus, the oblique rays have to traverse larger distances than the vertical rays. Consequently, the amount of solar energy lost due to reflection, scattering and absorption increases with increasing distance of travel path covered by the sun’s rays through the atmosphere (fig. 33.2). It may be summarized that the oblique rays lose more energy than the vertical rays while passing through the atmosphere.
(2) Length of Day:
If all the other conditions are favourable and equal then longer duration of sunshine (or length of day) and shorter duration of night enable the ground surface to receive larger amount of insolation. On the other hand, shorter the duration of sunshine and longer the period of night, the lesser the amount of insolation received at the earth’s surface. The length of day varies at all places except at the equator due to inclination of the earth’s axis, its parallelism and the earth’s rotation and revolution.
The length of day is always of 12 hours at the equator because the circle of illumination or light circle always divides the equator into two equal halves. But the length of day increases poleward with northward march of the sun in the northern hemisphere while it decreases in the southern hemisphere at the time of summer solstice (21 June).
On the other hand, the length of day increases from the equator pole-ward in the southern hemisphere but it decreases in the northern hemisphere at the time of winter solstice (22 December) (southward march of the sun). It is important to note that the duration of day becomes of 6 months at the North Pole from 21 March to 23 September during the northward migration of the sun while the night is of the duration of 6 months at the South Pole during this period.
Conversely, the length of day becomes of 6 months at the south pole (23 September to 21 March) during the southward migration of the sun while the night becomes of 6 months at the North Pole during this period. Inspite of increasing length of day from the equator towards the north pole during summer solstice and from the equator to the south pole during winter solstice amount of insolation received at the ground surface decreases considerably poleward because of decrease in the angle of sun’s rays.
Inspite of the longest length of day at the poles insolation becomes minimum because (i) the sun’s rays become more or less parallel to the ground surface, and (ii) the ice cover reflects most of the solar radiation. It is apparent that the angle of the sun’s rays controls the amount of insolation received more effectively than the length of day. It may be, thus, concluded, that the places having longer length of day and vertical sun’s rays will certainly receive maximum insolation.
(3) Distance between the Earth and the Sun:
The distance between the sun and the earth changes during course of a year because the earth revolves around the sun in elliptical orbit. The average distance between the sun and the earth is about 93 million miles (149 million kilometres). At the time of perihelion on January 3 the earth is nearest to the sun, say 91.5 million miles (147 million kilometres) away while at the time of aphelion on July 4 it is farthest from the sun, say 94.5 miles (152 million kilometres) away (fig. 33.3).
As per rule, the earth at the time of perihelion, when it is nearest to the sun, should receive maximum insolation while it should receive minimum insolation at the time of aphelion when the earth is at the greatest distance from the sun.
In fact, in the month of January, when the earth is nearest to the sun, there is winter season instead of summer season in the northern hemisphere due to low amount of insolation received.
On the other hand, in the month of July, when the earth is farthest from the sun, there is summer instead of winter in the northern hemisphere due to high amount of insolation received. It is obvious that factors of the angle of the sun’s rays and length of day play more dominant role in the distribution of insolation than the factor of varying distances between the earth and the sun.
Of course winters are 7 percent less severe in January in the northern hemisphere but summer is 7 per cent more intense in the southern hemisphere at the time of perihelion while summer is 7 per cent less intense in July in the northern hemisphere but winter is 7 per cent more intense in the southern hemisphere at the time of aphelion.
(4) Sunspots:
Sunspots are created in the solar outer surface due to periodic disturbances and explosions. The number of sunspots varies from year to year. The studies have shown that the variation in the number of sunspots is cyclic in nature. In other words, the increase and decrease of number of sunspots is completed in a cycle of 11 years. During every 11th year there is maximum number of sunspots.
The energy radiated from the sun increases when the number of sunspots increases and therefore the amount of insolation received at the earth’s surface also increases. On the other hand, the amount of insolation received at the earth’s surface decreases when the number of sunspots decreases.
(5) Effects of the Atmosphere:
The electromagnetic solar radiation or the incoming shortwave solar radiation has to pass through thick layer of the earth’s atmosphere and hence it is partly absorbed, partly reflected and partly scattered by the atmosphere and partly transmitted to the earth’s surface.
Absorption:
If the total amount of energy radiated from the sun towards the earth and its atmosphere (which is 1.2 billionth part of the total energy radiated from the photosphere of the sun) is taken to be 100 per cent, about 14 per cent of this amount is absorbed by the atmospheric gases (e.g., by ozone in the stratosphere to larger extent and oxygen and carbon dioxide to very limited extent), water vapour, haze etc.
The process of absorption is selective in nature. The shortest wavelengths ranging between 0.02 micron and 0.29 micron are absorbed by oxygen (O2) and ozone (O3) gases. Ozone also absorbs ultraviolet rays of the wavelengths varying from 1000 angstroms to 4000 angstroms and thus prevents these ultraviolet radiation waves from reaching the earth’s surface. Water vapour absorbs the incoming solar radiation waves of the wavelengths ranging between 0.9 micron and 2.1 microns.
Scattering:
Some portion of the incoming electromagnetic solar radiation (23%) is scattered in the atmosphere by dust particles and haze. Six per cent of this scattered energy is sent back to space while 17 per cent reaches the earth’s surface. The process of scattering is selective in nature. Scattering becomes possible when the diameter of invisible dust particles suspended in the air and the molecules of the atmospheric gases is shorter than the wave lengths of the solar radiation waves. Blue light of the incoming shorter wavelengths is more scattered than red light.
This is the reason that the sky looks blue. Similarly, the picturesque reddish hue of the, sky during sunrise (dawn) and sunset (twilight) is the result of scattering of all the colour spectra except the red and orange because at the time of sunrise and sunset the oblique rays have to pass through the longest path of the atmosphere.
Reflection:
The scattering of incoming solar radiation waves by dust particles and molecules of water vapour (clouds) when the diameter of these particles is longer than the wavelengths of incoming solar radiation is called diffuse reflection which sends some portion of incoming solar energy back to space while some portion remains in the lower atmosphere. The diffused and scattered solar energy present in the lower atmosphere enables us to see even the dark portion of the moon.
One can also see (if not suffering from cataract) even in the pitch darkness of night. Some of the scattered and diffused solar energy reaches the ground surface. Such energy is called as diffuse blue light of the sky or diffuse day light. Some portion of incoming solar radiation is reflected back to space by high clouds (27 per cent) and by the ice-covered ground surface (2 per cent).
The portion of incident radiation energy reflected back from a surface is called albedo. Various attempts have been made to measure total albedo of the earth (including its atmosphere). Various data derived so far indicate the earth’s average albedo fluctuating between 29 per cent and 34 per cent including the energy reflected through the mechanism of diffuse reflection by dust particles, water molecules etc., (from the cloud surface and from the earth’s surface).
The albedo of other planets has also been estimated e.g. Moon (7%), Mercury (6%), Mars (16%), Venus (76%) and the remaining outer planets (73% to 94%).
It may be pointed out that the processes of absorption, scattering and reflection are not as simple as discussed above rather they are highly complex. Furthermore, the figures used here to indicate the quantity of solar radiation lost during its passage through the atmosphere by different processes are mere estimates and these vary from the estimates of one scientist to the other.
Essay # 7. Measurement of Solar Radiation:
Different forms of solar radiation are:
1. Direct solar radiation.
2. Sky radiation or diffused radiation.
3. Global radiation.
4. Reflected radiation.
5. Thermal radiation.
6. Net radiation.
Campbell-Stroke Sunshine Recorder:
Duration of bright sunshine hours is measured with Campbell-Stroke sunshine recorder. The instrument consists of a glass sphere of 10 cm diameter, mounted concentrically in a section of a spherical bowl, to focus the sun rays sharply on a card held in grooves cut into the bowl (Fig. 2.13).
Three overlapping pairs of grooves are provided in the bowl to take cards suitable for different seasons during the year (Table 2.9 and Fig. 2.13).
Sunshine recorder is installed on a masonry pillar of 1.52 m (5 feet) above ground surface. The sphere is supported on the bowl and degree of bent is according to latitude of the station.
Pyranometers:
Depending on the requirement, different instruments are used for recording the data. Pyranometer (pyreheliometer previously) is used for measuring total incoming radiation.
There are several types of pyranometers:
1. Eppley pyranometer.
2. Bellani pyranometer.
3. Precision pyranometer
4. Licor pyranometer
5. Albedometer.
Net Radiometer:
As the name indicates, it is used for measuring net radiation flux. There are two sensors, which are exposed to the sky and earth. Sensor exposed to sky measures incoming radiation and the other facing the earth measures outgoing radiation.
Quantum Sensor:
The instrument is used for measuring photosynthetically active radiation (PAR). Tube solarimeters containing several quantum sensors are used for measuring the intercepted photosynthetically active radiation (IPAR) in the crop canopy and the quantum sensors for measuring PAR near the ground. Difference between the two gives the intercepted or absorbed PAR.
Spectro-Radiometer:
Solar radiation in narrow wave bands can be measured with this instrument. It measures radiation at an interval of 20 nm bandwidth between 400 and 1010 µm wavelength range. Relationship between plant architecture (plant morphology) and reflectance can be measured with this instrument.
Infrared Thermometer:
It can sense infrared radiation in the range of 8 to 14 µm. Surface temperature of the plants can be measured without contact. Canopy temperature of crop can also be measured from a distance for estimating plant water status.
In international standards (S.I. units), solar radiation is expressed in Watts cm-2. In meteorology, commonly used unit of radiation is calories cm-2 min-1.
1 Watt = 1 Joule s-1.
1 cal cm-2 min-1 = 697.93 W m-2
Essay # 8. Effect of Solar Radiation:
Climate Effects:
On earth, solar radiation is obvious as daylight when the sun is above the horizon. This is during daytime and also in summer near the poles at night, but not at all in winter near the poles. When direct radiation is not blocked by clouds, it is experienced as sunshine, combining the perception of bright white light (sunlight in the strict sense) and warming. Warming on the body, ground and other objects depends on absorption (electromagnetic radiation) of electromagnetic radiation in the form of heat.
The amount of radiation intercepted by a planetary body varies inversely with the square of the distance between star and planet. Earth’s orbit and obliquity change with time (over thousands of years), sometimes forming a nearly perfect circle and at other times stretching out to an orbital eccentricity of 5 per cent (currently 1.67%).
But the seasonal and latitudinal distribution and intensity of solar radiation received at earth’s surface also varies. For example, at latitudes of 65 degrees, change in solar energy in summer and winter can vary by more than 25 per cent as a result of earth’s orbital variation.
Because changes in winter and summer tend to offset, change in annual average insolation at any given location is near zero, but the redistribution of energy between summer and winter does strongly affect the intensity of seasonal cycles. Such changes associated with redistribution of solar energy are considered a likely cause for the coming and going of recent ice ages.
Life on Earth:
Existence of nearly all life one earth is fueled by light from the sun. Most autotrophs, such as plants, use the energy of sunlight, combined with minerals and air, to produce simple sugars—a process known as photosynthesis. These sugars are then used as building blocks and in other synthetic pathways which allow the organism to grow.
Heterotrophs, such as animals, use light from the sun indirectly by consuming the products of autotrophs, either directly or by consuming other heterotrophs. Sugars and other molecular components produced by autotrophs are then broken down, releasing stored solar energy and giving the heterotroph the energy required for survival. This process is known as respiration.
Light requirements of plants: Solar energy provides light required for seed germination, leaf expansion, growth of stem and shoot, flowering, fruiting and thermal conditions necessary for physiological functions of the plant. Solar radiation plays an important role as regulator and controller of growth and development. Solar radiation also influences assimilation of nutrient and dry matter distribution.
The basic principle for increasing yield is harvesting more solar energy. All the management practices like optimum time of sowing, optimum plant population, timely application of fertilizers, irrigation management etc. are aimed at increasing the interception of solar radiation by foliage so as to get more yield.