Most water loss occurs through the leaves of plants. Therefore the equation is to be applied to large, extensive surfaces of homogeneous vegetation only. Reduce the ppm used, as you are putting on morevolume than a standard drench where you know how much volume was applied andwhat ppm was used. Seed hardening for 40 0 C for 12 hrs 53. In such vegetative propagated portions, transpiration is reduced to avoid wilting of organs or tissues since flaccid cells do not grow. Temperature : A rise in temperature of the leaf or both leaf and air, within a certain physiological range, will increase the rate of transpiration.
Removal of unwanted vegetation helps the main crop obtain greater accessibility to soil moisture and plant nutrients for its own growth. The beneficial effect of shelterbelts is seen more clearly in drought years. Hence antitranspirants are chemicals which on application to crop plants reduce transpiration. For example, at 20°C, l is about 2. Antitranspirant is any material applied to transpiring plant surfaces for reducing water loss from the plant. This fraction decreases over the growing period as the crop develops and the crop canopy shades more and more of the ground area. Adoption of the agrotechniques is the only solution for farmers of dryland and water stressed scenario to save millions of world population in millennium especially in the developing countries, like India.
Antitranspirants are compounds that are designed to reduce the loss of water vapor from plants, a process known as transpiration. Drought during the critical phenological phase like flowering and grain development is highly detrimental. There are other ways e. Leaf structure : Plants growing in dry areas show a number of structural modifications, especially in leaves, such as thick cuticle, thick cell well, well-developed palisade, sunken stomata, a covering of hairs, etc. Evaporation from an open water surface provides an index of the integrated effect of radiation, air temperature, air humidity and wind on evapotranspiration.
Evapotranspiration is not easy to measure. Role of Vegetation Vegetation is crucial in preserving productive soil and conserving rain water for sustaining life. Moreover, procedures have been developed for estimating missing climatic parameters. There are of four types. The supply of water can be inadequate due to the following reasons: i Water in the soil about the roots reaches wilting co-efficient, ii Root system is not adequate to supply the top, iii A low soil temperature, and iv A high concentration of soil solution. The rise in temperature accelerates evaporation from the outer surface of the cell walls of mesophyll cells into the intercellular spaces of the leaf and the open stomata help diffusion.
If transpiration stops, there would be an enhanced loss of heat by radiation and convection because of the increased leaf temperature. A large number of empirical or semi-empirical equations have been developed for assessing crop or reference crop evapotranspiration from meteorological data. Hence, radiation, air temperature, air humidity and wind terms should be considered when assessing transpiration. The effect of the chemical should persist for some-time. Mechanical Methods Where the slope of the soil is more than permissible, mechanical measures such as bunding, terracing and trenching are recommended in addition to agronomic methods. Crop evapotranspiration can be calculated from climatic data and by integrating directly the crop resistance, albedo and air resistance factors in the Penman-Monteith approach. It also conserves soil, and due to increased time of concentration, more rainwater seeps through the soil profile to recharge ground water.
Specific devices and accurate measurements of various physical parameters or the soil water balance in lysimeters are required to determine evapotranspiration. This is due to higher number of stomata per unit area, more extensive venation, greater internal evaporating surfaces exposed to the internal atmosphere in xerophytic leaves as compared to mesophytic leaves. Wind: Wind increases evaporation and consequently transpiration by removing the moist air from the surface of the leaf and replacing it by drier air, thereby increasing the saturation pressure deficit. In addition, winds of high velocity may cause stomatal closure. Ideal for most trees, vines, turf, flower and vegetable crops.
Optimum turgidity: It is generally argued that there is an optimum level of water potential within the plant. In addition leaf size and shape, spacing, distribution and structure of stomata, water content of leaves greatly affect the rate of transpiration. Water leaves the guard cells and enters the leaf parenchyma. These features reduce water loss. Apart from the water availability in the topsoil, the evaporation from a cropped soil is mainly determined by the fraction of the solar radiation reaching the soil surface. Should be non-toxic to various life forms, iii.
Similarly when the water potential becomes highly negative growth also stops. The methods are often expensive, demanding in terms of accuracy of measurement and can only be fully exploited by well-trained research personnel. The water, together with some nutrients, is taken up by the roots and transported through the plant. Vertical mulching To improve infiltration and storage of rainwater in these soils, vertical mulches are formed. Another method of estimating evapotranspiration is the mass transfer method. Therefore the evapotranspiration process is governed by energy exchange at the vegetation surface and is limited by the amount of energy available. Agronomic methods are used in inter-bunded areas and mechanical practices complement to help boost crop yields in rainfed drylands.
One of the most widely used antitranspirants compounds is acetylsalicylic acid which is used in low concentrations and also endogenously reported in some plants. Evaporation is the process whereby liquid water is converted to water vapour vaporization and removed from the evaporating surface vapour removal. Bothchemicals work on a wide range of plants, get in quickly like A-Rest but havelonger-lasting effects on plant growth. Farmers can also raise wind belts across the wind direction. Wind : Stomata close when the leaf is exposed to high wind velocities.