AGRO-101_T_13. growth and development of crops.pptx

Growth and development of crops

1. Lecture 13 Growth and development of crops – factors affecting growth and development.

2. Introduction Crop growth is defined as “ irreversible increase in size , measured as dry weight which occurs throughout the crop life cycle”. It may be expressed in terms of dry weight, length, height or diameter. Crop development is the progression through the morphological changes which occur during growth of the crop. It is more readily described qualitatively than quantitatively. For example, development of a crop plant from germination to maturity

3. Growth Development Growth is the increase in vigour , size, shape, height, volume and weight Development is the phase wise progress of an individual Growth is irreversible Development is a continuous process It is a quantitative character It is a qualitative character It can be measured It cannot be measured but can be visualized Some aspects of growth (e.g., height) may be irreversible . Some developmental changes can be influenced or corrected under certain conditions. Influenced by environmental factors like sunlight, water, and nutrients. Influenced by both genetic factors and environmental conditions. It may stops at maturation It is a continuous process

4. Weather elements i . Air temperature ii. Solar radiation iii. Precipitation iv. Wind v. Composition of the atmosphere

5. Effect of weather elements on crop growth It is a measure of intensity of heat. Temperature required for the growth is ranging from 5 to 45 C. It directly influences photosynthesis, respiration, cell wall permeability, nutrient and water absorption, transpiration, enzyme activity and protein coagulation. In Castor--High day temperature of >32°C promotes male tendency; low day temperature of <30°C promotes female tendency. i . Air temperature:

6. ii. Solar Radiation: This is the radiant energy from the sun, measured as a total amount (direct solar plus sky radiation) expressed in cal cm -2 min -1 measured by Pyrheliometer . For photosynthesis, only visible part of the total solar energy is of importance. Photosynthesis in green leaves use solar energy in wavelengths from 0.4 to 0.7 micrometers (µm), often referred to as photosynthetically active radiation (PAR) or simply light. Radiant energy influences the protoplasm permeability, intake and loss of water, enzyme activity, respiration, photosynthesis, flower initiation and ripening of fruits. Three aspects of light-intensity (quantity), duration (day length) and quality (spectral distribution).

7. iii.Precipitation : The essential requirement of water for plant growth can be visualized from the fact that it may constitute 70-95% of total fresh weight when it is actively growing. Precipitation is the major source of soil moisture for crop growth in dry regions during rainy season. A number of physiological processes in crop growth is affected due to water stress. Cell growth, cell wall and protein synthesis are adversely affected by the stress. Stomatal closure due to water stress restrict CO 2 intake leading to reduced photosynthesis. Precipitation also influences atmospheric humidity . High humidity can increase the risk of disease and pest outbreak Consequences of high intensity rains of long duration (floods) on crop production are well established.

8. iv. Wind: Plant responses to wind. Wind over the crop surface can alter the onset of drought during dry periods due to water vapor loss through transpiration. This may lead to stomatal closure and reduce rate of gaseous exchange leading to reduced photosynthesis and crop growth. Strong winds in association with rain can cause lodging, particularly at flowering in cereals . Provision of windbreaks in exposed areas can minimize the adverse effects of high wind speed. Growth of plants, in general, seems to be inhibited at wind speeds above 10kmph. However, there are individual variations.

9. v. Composition of the atmosphere:

10. v. Composition of the atmosphere: Certain gases, such as sulphur dioxide (SO 2 ),carbon monoxide (CO) and hydrofluoric acid (HF) when released into air in sufficient quantities are toxic to plants. Acid rain is often due to relatively high concentrations of sulphur dioxide and sulphates. Some of the effects that acid rain can have on plants and soil include increased leaching of inorganic nutrients, damage to leaves at pH<3, reduced microbial activity, reduced availability of soil nitrogen, etc. Injury to vegetation by fluorine released during the manufacture of metallic aluminum and the production of phosphatic fertilizers has been reported.

11. Weather and soil elements affecting crop production

12. 2. Soil elements i . Soil air ii. Soil temperature iii. Soil moisture iv. Soil reaction (pH) and v. Mineral nutrient supply

13. Soil can be defined as “Soil is a thin layer of the earth’s crust which serves as a natural medium for the growth of plants”. Soils are formed by the disintegrations & decomposition of parent rocks due to weathering and the action of soil organisms & also the interaction of various chemical substances present in the soil. Soil is formed from parent rock by the process of weathering over a long period by the action of rain water, temperature and plant & animal residues. A vertical cut of 1.5 to 2 m deep soil indicates a layer varying from a few cm to about 30 cm of soil, called surface soil, below that a layer of sub soil & at the bottom, the unrecompensed material which is the parent rock.

14. Role of soil: Soil is the natural media to grow the crop. Soil gives the mechanical support & act as an anchor, Soil supplies the nutrients to the crop plants, Soil conserves the moisture which is supplies to the crop plants Soil is an abode (house) of millions of living organisms which act on plant residues & release food material to plants Soil provides aeration for growth of crop and decomposition of organic matter.

15. Effect of soil elements on crop growth The percentage by volume of soil occupied by air under field conditions or at a given suction has been suggested as a measure of soil aeration status. As a rule, higher the bulk density, more compact the soil and smaller the amount of pore space. These situations restrict the plant growth due to its influence on root as well as shoot growth. High bulk densities inhibit the emergence of seedlings, increase mechanical resistance to root penetration and decrease the O2 supply to root system resulting in poor growth and yield of crops. Crops differ widely in their sensitivity to O2 supply. i . Soil air:

16. ii. Soil temperature: It influences root growth and functions . The rate of germination and emergence depends on soil temperature, as this can determine the survival of seedlings in rapidly losing soil moisture after sowing. Since most seeds are sown a depth of 2 to 5 cm , soil temperature can influence crop establishment.

17. iii. Soil moisture: Ability of soil to hold water( WHC ) is most important. Soil texture, structure and depth determine its moisture retention capacity to meet the crop needs. Soil texture influences its drainage characteristics and risk of erosion. Soil structure determines its suitability for arable farming. Efficient use of inputs in crop production depends on optimum levels of soil available moisture.

18. Functions of water Major component of the plant body (90%) Act as solvent for dissolving the nutrients & nutrient carrier Maintains/regulates the temperature of plant & soil as well Maintains the turgidity of plant cells Essential for absorption of nutrients & metabolic process of the plants Plant tissues constitute about 90% of water. Rain and ground water are the sources of the water. Ground H 2 O is reused for irrigation through well, tank or canal, etc. Erratic rains are to be conserved properly so that plants make best use of it. Rainwater is to be supplemented by irrigation to meet the water requirement of crops for bumper yields.

19. Water present in the soil helps the plants in many ways Supplies the essential raw material for production of carbohydrates by photosynthesis. Promotes physical, chemical & biological activities in the soil. Gaseous diffusion in soil for proper aeration Water is the life of plant and must be supplied in proper quantity. much water may suffocate the plant roots & too little may not be able to sustain the plant The water requirement of crops differs from crop to crop & variety to variety as well, depending upon the growth habit, genetically & physiological make up, duration of the crop, etc. For example, sugarcane, rice, banana, wheat, groundnut, etc. are the High water requiring crops Jowar, Mung, urad, Tur, gram, bajra etc. are the low water requiring crops.

20. iv. Soil reaction (pH): Availability of plant nutrients depends on soil reaction. Acid soils with high Fe, Al, and Mn decrease the availability of phosphorus. Availability of Mo declines with decrease in pH. Ammonical fertilizers left on soil surface are subjected to loss by volatilization at pH more than 7. Water soluble phosphate will be converted into unavailable form around pH 8.

21. v. Mineral nutrient supply: Capacity of the soil to supply essential plant nutrient elements has profound influence on crop production. Soil analysis provides estimates of the levels of available nutrients for determining the suitability of a soil for a particular crop and in formulating more precisely the fertilizer requirements. The inherent capacity of soil to supply amount of adequate nutrients to plants in balanced form is known as soil fertility while soil productivity is the capacity of soil to yield crops per unit area.