Factors affecting crop growth and production include climatic factors (temperature, rainfall, light, humidity, wind), edaphic factors (soil type, fertility, pH, moisture), and biological factors (pests, diseases, weeds, crop competition). Management factors like irrigation, nutrient management, cropping systems, and timely agricultural practices also play a crucial role.

1. Unit II Seasons and System of farming
Dr. S. Marimuthu., Ph.D.
Asst. Professor (AGR)
Factors affecting crop production

2. Factors
• A circumstance, fact, or influence that contributes to a result

3. Factors affecting crop production
Crop level Production system level
Y= G+E (G x E)
Where,
• Y= Yield
• G= Genotype
• E= Environment
• G x E= Interaction

4. Factors affecting crop production
• Internal Factors
• Climatic
• Edaphic (soil)
• Biotic
• Physiographic (Slope)
• Socioeconomic or
Anthropic (Man)
• External Factor
(Environmental)
• Genetic factors

5. Internal factors - Genetic factors
• High yielding ability
• Early maturity
• Resistance to lodging
• Drought, flood and salinity tolerance
• Tolerance to insect pests and diseases
• Chemical composition of grains (oil
content, protein content )
• Quality of grains (fineness, coarseness)
• Quality of straw (sweetness, juiciness)
Genetic
make up

6. External factors – Environmental factor
• Plant growth and development - To governed by
soil and climate
• Success or failure - Prevailing weather condition
• Modification of weather - Adjusting cropping
pattern
• More than 50 % yield variation
• Sound knowledge on climate and the biological
process of plant - Essential to a scientific farming

7. Climatic factors
• Precipitation
• Temperature
• Atmospheric humidity
• Solar radiation
• Wind velocity
• Atmospheric gases

8. Precipitation
• All water falls from atmosphere - Rainfall, Snow,
Hail, Fog and Dew
• Dew: condensation of water vapour present in
the air
• Rainfall - important factor influences vegetation
of a place
• Most crops receive water supply from rainwater
• Its amount and distribution, affects the choice
crops

9. Precipitation
• In desert areas grasses and shrubs are common where hot desert
climate exists
RF - Low & Uneven
distribution
Dry land
farming
Nutri – Ceraals
RF - Heavy &
Even distribution
Plains Western gates
Rice Tea, Coffee &
Rubber
Soil and
Vegetation

10. Precipitation
• Distribution of rainfall is more important than total rainfall
in drylands
Yield Amount of Rain fall
Low
yield Rain fall excess the optimum
Nutrient
Loss
Exceeds Infiltration rates, Run off
with Soil Erosion

11. Temperature
• It is intensity of heat energy
• 15 and 40o C for plant growth
• Temperature of a place - determined by
it’s distance from the equator (latitude),
altitude
• The minimum, optimum and maximum
temperature of individual’s plant -
Cardinal temperature

12. Cardinal temperature
Crops Min. temp (oC) Opt. temp (oC) Max. temp (oC)
Rice 10 32 36-38
wheat 4.5 20 30-32
Maize 8-10 20 40-43
Sorghum 12-13 25 40
Tobacco 12-14 29 35

13. Pattern of biome distribution
• Large group of land ecosystems with similar climates and
organisms

14. Classification of crops based on temperature
Cool season crops
• Grown in cool weather period (Nov to Feb)
• Wheat, Barley, potato, Oats, sugarbeet etc.,
• Cardinal temp: Min:0-5;Opt:25-30; Max:30-
38oC
Warm season crops
• Grown in summer & monsoon (Mar- Sept)
• Rice, Sorghum, Maize, Sugarcane, Bajra,
Groundnut
• Cardinal temp: Min:15-20; opt:30-38; Max:45-
50

15. Classification of vegetation based on temperature
Class Region
Temp
conditions
Vegetation
Common
crops
Megatherms
Equatorial/
tropical
High temp
throu’ year
Tropical rain
Cassava,
rubber, rice
Mesotherms
Tropical/
subtropical
High temp with
low temp
winter
Tropical
deciduous
forests
Maize,
sorghum, etc
Microtherms Temperate Low temp
Mixed
coniferous
Wheat, oats
potato
Hekistotherms
Artic/
alpine
Very low temp Alpine Pines, spruce
• Eurythermic plants – Wide range of temperature - Freezing to 55°C
• Stenothermic plants – Narrow range of temperature - Aquatic

16. Influence of temperature on growth
• Biochemical reactions: At opt temp range the
biochemical reaction increases with increase in
temp.
• Rate of reaction may double for every 10 oC
increase - Quotient10 (Q10))
• Uptake of CO2: The opt temp for net CO2 uptake
is 24oC for wheat and Barley

17. Influence of temperature on growth
• Enzyme activity: Temp increases the activity of
enzymes
• Rate of photosynthesis: Low temp reduced the
rate of PS - Eg. Maize (10oC for 10 days, the rate
of PS reduced by 33%)
• Influence on growth regulators: At opt temp
the activity of auxin, gibberellins and cytokinin
(growth promoters) are high and the activity of
abscisic acid is low (growth retardant)

18. High temperature on growth of plants
• Nutrient uptake is reduced (Absorption of
calcium is reduced at 28oC in maize)
• Affects shoot growth in temp. crops (wheat)
• Abortion of pollen or loss of viability of pollen
• High temp. with high RH favours plant diseases
Lace bug
Mealy bug
Rot diseases

19. High Temperature
• Most of the Plants killed at 50-
60°C – Thermal death point
• Sun clad: Temperature
fluctuation - Death of tissue in
bark - high day temperature and
low night temp.
• Stem griddle: Scorching of
shoots of young seedling near
ground surface - summer cotton

20. High temp stress
Heat injury
• Very high temperature often
stops growth
• The plant faces incipient
starvation due to high
respiration rate.
• The plant stunted and if the
condition continuous the plant
will die

21. High Temperature
• Dehydration of protoplasm & Cell
protein precipitate
• Evaporation and Respiration will
be more
• Enzymes are affected
• Maturity advances
• Absorption and translocation of
nutrient affected

22. High temperature on growth of plants

23. Low temp stress
• Affect - survival, cell division and elongation, PS, water transport,
vegetative and reproductive growth
• C4 plants under 10 oC,
the activity of pyruvate
dikinase is reduced - less
PS
• Entry of water into the
plant is restricted (low
permeability of cells)

24. Low temp stress
• Temperate crops - Vegetative
(low temp) and high temp at
maturity (wheat, veg -10,
reproductive 18 and grain
develop 20oC)
• Tropical crops high temp during
early stage and low temp at
maturity (Rice veg 31, flowering
30 and ripening 20oC)

25. Low temp stress
Chilling injury
• Plants growing in hot
climate if exposed to low
temp for sometime, are
found to be killed or injured
severely.
• Eg: Chlorotic bands on
leaves of sugarcane and
maize, exposed to 4oC for
60 hours

26. Low temp stress
Freezing injury
• Plants exposed to low temperature,
water in intercellular spaces frozen into
ice crystals (Temperate region) further
low temp - increase size of ice crystals -
Distortion of cell (Death of cell)

27. Low temp stress
• Suffocation: During winter ice/snow -
crop suffers for want of oxygen - Ice
in contact with roots inhibits diffusion
of CO2 restricting root respiration
• Heaving Injury: Plants caused by
lifting upward of the plant along with
soil from it’s normal position in
temperate regions where snowfall is
common

28. Atmospheric Humidity
• Humidity - Water is present in the
atmosphere in the form of
invisible water vapour
• Relative humidity - Ratio between
the amount of moisture present in
the air to the saturation capacity
of the air at a particular
temperature
• RH - 100% it means that the entire
space is filled with water

29. Atmospheric Humidity
• Very low and very high relative
humidity is not suitable for crop
production
• RH - 40 – 60% is suitable for most
of the crops
• RH - 80% and above, high chance
for the outbreak of pest and
disease, e.g., Brown plant hopper
(BPH) in rice multiplies enormously

30. Atmospheric Humidity
• Influenced by temperature and
pressure of a particular place
• ET of crop plants increases with
temperature but decreases with
high RH affecting quantity of
Irrigation water
• Moist air favours the growth of
fungi and bacteria - affect crop
growth
• Blight disease of potato and tea
spread fast during moist weather

31. Solar radiation
• Primary source of heat energy for earth and its
atmosphere
• 99% of the energy to biosphere from the sun
• one per cent is from
• Stars,
• Lightning discharge,
• Sun’s radiation reflected from the moon,
• Re-radiation from the earth etc.

32. Solar radiation
• Solar energy provides light energy required for
photosynthesis and many other functions like
seed germination, leaf expansion, growth of
stem and shoot, flowering, fruiting and
thermal conditions for physiological functions
of the plant

33. Solar constant
• Solar energy received on a unit area at
the outer most boundary of the earth
spherical per unit time
• 1.88 g cal. cm-2 min-1 in June
• 2.02 g cal. cm-2 min-1 in January
• Average value is 1.94 g cal. cm-2 min-1
• 35% by UV and visible segment & 65%
by infrared segment

34. Reflectivity – Albedo
• Ratio of radiant energy
reflected to the total
incident radiation
• The percentage
expression is albedo
• Measured by
albedometer
• The earth albedo value
is approximately 35%
Is the reflectivity of a surface

35. Thermal effect of radiation
• >70 % of solar radiation
absorbed by plants is
converted into heat
• This heat energy is utilized
for transpiration and for
convective heat exchange
with surroundings

36. Photosynthetic effect of radiation
• A portion of solar radiation upto 28 % of energy is used in photosynthesis
• Light is indispensable for the synthesis of the most important pigment of
the plant –Chlorophyll
• Chlorophyll - absorbing radiant energy and converting it into potential
chemical energy of carbohydrates
• Regulate opening and closing of stomata
• Light affects the plants through it’s
• Intensity
• Quality
• Duration

37. Effect of light intensity
Low light intensity
• Causes stomatal closure
• CO2 entry restricted –
photosynthesis reduced
• Low plant growth, short
internodes and spikelet
sterility
High light intensity
• Respiration rate increase
• More water loss or transpiration
• Cell content will be oxidized at
very high light intensity called
Photo oxidation (or) Solarisation
• Leaf surface will decrease but
thickness increase

38. Duration of light
• Important for selection of crop variety
• Photoperiodism (Required relative length of the day & night,
especially for floral initiation)
• Short-day plants: Flower initiation required <10 hrs
• E.g. Rice, Jowar, Maize, green gram, black gram etc.
• Long day’s plants: Flower initiation >10 hrs E.g. Wheat, Barley,
Sugarbeet and Potato
• Day neutral plants: Photoperiod does not have much influence for
phase change for these plants. E.g. Cotton, sunflower, Buck wheat

39. Quality of light
VIBGYOR - is the Photosynthetic Active Radiation (PAR) – 400 to 750 nm
• V - Violet - 390 - 430 nm
• I - Indigo - 430 - 470 nm
• B - Blue - 470 - 500 nm
• G - Green - 500 - 560 nm
• Y - Yellow - 560 - 600 nm
• O - Orange - 600 - 650 nm
• R - Red - 650 - 750 nm

40. Quality of light
• Colours used for photosynthesis is violet-blue
and orange red regions
• Red light - most favourable for plant growth
• Shorter wavelength of UV rays, X rays and
Gamma rays and infrared rays - detrimental
crop growth
• UV and shorter wavelengths are scattered and
infrared and longer wavelengths are absorbed
by moisture of the atmosphere
• “Diffused light or sky light”

41. Wind Velocity
• Wind is to carry moisture and heat (also
supplies fresh CO2 for the PS)
• Mild wind is essential for crop production
(4 – 6 km/hour)
• High wind - mechanical damage of the crops
(i.e.) it removes leaves and twigs
• ET also increases with increase in wind speed
(frequent irrigation)
• Availability of CO2 and flow of nutrients are less
and Soil erosion. It also helps pollination

42. Wind Velocity
• Velocity of wind at a place depends on
geographical situation, topography, altitude and
distance from sea shore
Mechanical damage
• Lodging of crop and trees due to violent winds
• In bare soil, wind cause severe soil erosion
Physiological effects
• Higher wind speed leads to more ET loss
• Hot dry winds - damage at flowering time
• Internal water balance of plants is affected

43. Benefits - Wind Velocity
• Wind is also responsible for rainfall - In India
monsoon type of winds are mainly due to wind
movements
• Wind helps in pollination of flowers
• Hot dry winds reduce the incidence of yellow rust of
wheat
• Moderate wind have a beneficial effect on
photosynthesis
• Net Assimilation Rate and Relative Growth rate (RGR)
are increased with increase in wind speed from 2.5 to
7.0 m/s in barley and rice

44. Provisions to reduce the ill effect of wind
Wind break
• Structure to reduce the
wind speed
• Hedge, Tree along the
border rows
• Any other – structure to
reduce heat or cold
waves some extent

45. Provisions to reduce the ill effect of wind
Shelter belt
• Block or multiple rows of trees
with or without shrubs
• Several rows – 3 to 9
• Protection against heat and
cold waves and wind speed –
velocity reduces to 10 times of
the tree height at wind ward
side 30 times at leeward sides

46. Atmospheric gases on plant growth
• CO2 – is important for Photosynthesis, CO2 taken by the plants by
diffusion process from leaves through stomata
• CO2 is returned to atmosphere during decomposition of organic
materials & farm wastes

47. Atmospheric gases on plant growth
• O2: is important for respiration of
both plants and animals
• Nitrogen: one of the important major
plant nutrient, Atmospheric N is fixed
in the soil by lightning, rainfall and N
fixing microbes in pulses crops
• Certain gases like SO2, CO, CH4, HF
released to atmosphere are toxic to
plants

48. Edaphic factors
• Soil moisture
• Soil air
• Soil temperature
• Soil mineral matter
• Soil organic matter
• Soil organisms
• Soil reaction
• The factors which relate to structure
and composition of soil
• Physical, Chemical and Biological

49. Soil moisture
• The moisture is held within the soil
(attractive forces)
• Available soil moisture range between
saturation point and wilting point
Soil air
• Absolutely essential for the
absorption of water by roots
• O2 - respiration of roots and
microorganisms
• Breaking down the insoluble
mineral into soluble salts
• Decomposing organic matter

50. Soil temperature
• Influences the rate of absorption of
water and solutes (20°C and 30°C),
• Germination of seeds and rate of
growth of the underground
portions of the plants
Soil mineral matter
• Derived - weathering of the rooks
and minerals
• Plant nutrients (Si, Ca, Mg, Fe, K, Na
and Al)
• Minor (B, Mo, Zn, Cu, Co, I & Fe)

51. Soil organic matter
• Influence on the soil properties and
growth of crops
• Derived from dead and decaying or
added into the soils (Plants and
animal)
Soil organism
• Break down the organic matter
Flora Macro flora Roots of higher plants
Micro flora Bacteria, Actinomycetes,
Fungi, Algae
Fauna Macro fauna Earthworms, Burrowing
vertebrates
(moles, gophers, rats, etc.)
Micro fauna Protozoa, Nematodes,
Mites, Insects

52. Soil reaction
• Describes the degree of acidity or
alkalinity - terms of concentration
of H/OH ions
• Neutral soils - best for growth of
most crops

53. Biotic factors - plants
Competitive and complimentary nature
among field crops
• Competition between plants (nutrients,
moisture & sunlight)
• Cereals & legumes - mixed cropping -
mutual benefit -better yield
Competition between weed and crop
• Weeds reduce crop yields ( compete with
resources)
Plants as Parasites
• Dependent on its host (striga, orabanche,
cuscuta &loranthus)
Symbiosis
• Mutual relationship with each other &
with the environment
• Legumes and rhizobia–nodule forming

54. Biotic factors - animals
• Soil animals or Soil fauna include
protozoa, nematode, rotifers, snails
and insects
• Harmful organisms - Insects and
nematodes - damage crops –
storage grains (20% )
• Beneficial organisms - pollinated by
insects (Bees, wasps, Moths,
butterfly & beetles), Burrowing of
earthworm (aeration & drainage of
the soil)
• Small animals - rabbits, squirrels and
field rats - excessive damage to crops
• Large animals - Domestic animals and
wild animals- damage to crop plants

55. Physiographic factors
• Geological Strata
• Its not for parent material utilized -
nature of crops grown in these soils
• Topography - nature of the surface of earth
• Altitude of the place – increase temp
• Steepness of slope - run off
• Exposure of the slope to light and wind -
weak intensity of light and strong dry winds
• Direction of the mountain chains -
Distribution of the rainfall during monsoon -
type of crops in dry farming

56. Anthropic (socio economic) factors
• Man / women produce
changes in plant environment
and are responsible for
scientific crop and soil
management,
• Breeding varieties for
increased yield, and
• Introduction of exotic plants

57. Thanks a lot