Plant nutrition

 Plant nutrition

 Plant nutrition is the study of the chemical elements and compounds necessary for plant growth, plant metabolism and their external supply. In its absence the plant is unable to complete a normal life cycle, or that the element is part of some essential plant constituent or metabolite. This is in accordance with Justus von Liebig's law of the minimum.[1] The total essential plant nutrients include seventeen different elements: carbon, oxygen and hydrogen which are absorbed from the air, whereas other nutrients including nitrogen are typically obtained from the soil (exceptions include some parasitic or carnivorous plants).

Plants must obtain the following mineral nutrients from their growing medium:-[2]

·         the macronutrients: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sulfur (S), magnesium (Mg), carbon (C), oxygen (O), hydrogen (H)

·         the micronutrients (or trace minerals): iron (Fe), boron (B), chlorine (Cl), manganese (Mn), zinc (Zn), copper (Cu), molybdenum (Mo), nickel (Ni)

These elements stay beneath soil as salts, so plants consume these elements as ions. The macronutrients are consumed in larger quantities; hydrogen, oxygen, nitrogen and carbon contribute to over 95% of a plant's entire biomass on a dry matter weight basis. Micronutrients are present in plant tissue in quantities measured in parts per million, ranging from 0.1[3] to 200 ppm, or less than 0.02% dry weight.[4]

Most soil conditions across the world can provide plants adapted to that climate and soil with sufficient nutrition for a complete life cycle, without the addition of nutrients as fertilizer. However, if the soil is cropped it is necessary to artificially modify soil fertility through the addition of fertilizer to promote vigorous growth and increase or sustain yield. This is done because, even with adequate water and light, nutrient deficiency can limit growth and crop yield.

Contents

·         1Processes

·         2Functions of nutrients 

2.1Macronutrients (derived from air and water)

2.1.1Carbon 2.1.2Hydrogen 2.1.3Oxygen 

2.2Macronutrients (primary) 2.2.1Nitrogen 2.2.2Phosphorus 2.2.3Potassium 

2.3Macronutrients (secondary and tertiary) 2.3.1Sulfur 2.3.2Calcium 2.3.3Magnesium 

2.4Micro-nutrients  2.4.1Iron 2.4.2Molybdenum 2.4.3Boron 2.4.4Copper 2.4.5Manganese 2.4.6Sodium 2.4.7Zinc 2.4.8Nickel 2.4.9Chlorine 2.4.10Cobalt 2.4.11Aluminum 2.4.12Silicon 2.4.13Vanadium 2.4.14Selenium

·         3Nutrient deficiency

·         4Nutrient status of plants

·         5Plant nutrition in agricultural systems

·         5.1Hydroponics

Processes.

Plants take up essential elements from the soil through their roots and from the air (mainly consisting of nitrogen and oxygen) through their leaves. Nutrient uptake in the soil is achieved by cation exchange, wherein root hairs pump hydrogen ions (H+) into the soil through proton pumps. These hydrogen ions displace cations attached to negatively charged soil particles so that the cations are available for uptake by the root. In the leaves, stomata open to take in carbon dioxide and expel oxygen. The carbon dioxide molecules are used as the carbon source in photosynthesis.

The root, especially the root hair, is the essential organ for the uptake of nutrients. The structure and architecture of the root can alter the rate of nutrient uptake. Nutrient ions are transported to the center of the root, the stele, in order for the nutrients to reach the conducting tissues, xylem and phloem.[5] The Casparian strip, a cell wall outside the stele but within the root, prevents passive flow of water and nutrients, helping to regulate the uptake of nutrients and water. Xylem moves water and mineral ions within the plant and phloem accounts for organic molecule transportation. Water potential plays a key role in a plant's nutrient uptake. If the water potential is more negative within the plant than the surrounding soils, the nutrients will move from the region of higher solute concentration—in the soil—to the area of lower solute concentration - in the plant.

There are three fundamental ways plants uptake nutrients through the root:

1.      Simple diffusion occurs when a nonpolar molecule, such as O2, CO2, and NH3 follows a concentration gradient, moving passively through the cell lipid bilayer membrane without the use of transport proteins.

2.      Facilitated diffusion is the rapid movement of solutes or ions following a concentration gradient, facilitated by transport proteins.

3.      Active transport is the uptake by cells of ions or molecules against a concentration gradient; this requires an energy source, usually ATP, to power molecular pumps that move the ions or molecules through the membrane.

Nutrients can be moved within plants to where they are most needed. For example, a plant will try to supply more nutrients to its younger leaves than to its older ones. When nutrients are mobile within the plant, symptoms of any deficiency become apparent first on the older leaves. However, not all nutrients are equally mobile. Nitrogen, phosphorus, and potassium are mobile nutrients while the others have varying degrees of mobility. When a less-mobile nutrient is deficient, the younger leaves suffer because the nutrient does not move up to them but stays in the older leaves. This phenomenon is helpful in determining which nutrients a plant may be lacking.

Many plants engage in symbiosis with microorganisms. Two important types of these relationship are

1.      with bacteria such as rhizobia, that carry out biological nitrogen fixation, in which atmospheric nitrogen (N2) is converted into ammonium (NH+ 4); and

2.      with mycorrhizal fungi, which through their association with the plant roots help to create a larger effective root surface area. Both of these mutualistic relationships enhance nutrient uptake.[5]

The Earth's atmosphere contains over 78 percent nitrogen. Plants called legumes, including the agricultural crops alfalfa and soybeans, widely grown by farmers, harbour nitrogen-fixing bacteria that can convert atmopheric nitrogen into nitrogen the plant can use. Plants not classified as legumes such as wheat, corn and rice rely on nitrogen compounds present in the soil to support their growth. These can be supplied by mineralization of soil organic matter or added plant residues, nitrogen fixing bacteria, animal waste, through the breaking of triple bonded N2 molecules by lightning strikes or through the application of fertilizers.

Functions of nutrients.

Further information: Soil § Nutrients

At least 17 elements are known to be essential nutrients for plants. In relatively large amounts, the soil supplies nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur; these are often called the macronutrients. In relatively small amounts, the soil supplies iron, manganese, boron, molybdenum, copper, zinc, chlorine, and cobalt, the so-called micronutrients. Nutrients must be available not only in sufficient amounts but also in appropriate ratios.

Plant nutrition is a difficult subject to understand completely, partially because of the variation between different plants and even between different species or individuals of a given clone. Elements present at low levels may cause deficiency symptoms, and toxicity is possible at levels that are too high. Furthermore, deficiency of one element may present as symptoms of toxicity from another element, and vice versa. An abundance of one nutrient may cause a deficiency of another nutrient. For example, K+ uptake can be influenced by the amount of NH+ 4 available.[5]

Nitrogen is plentiful in the Earth's atmosphere, and a number of commercially-important agricultural plants engage in nitrogen fixation (conversion of atmospheric nitrogen to a biologically useful form). However, plants mostly receive their nitrogen through the soil, where it is already converted in biological useful form. This is important because the nitrogen in the atmosphere is too large for the plant to consume, and takes a lot of energy to convert into smaller forms. These include soybeans, edible beans and peas as well as clovers and alfalfa used primarily for feeding livestock. Plants such as the commercially-important corn, wheat, oats, barley and rice require nitrogen compounds to be present in the soil in which they grow.

Carbon and oxygen are absorbed from the air while other nutrients are absorbed from the soil. Green plants ordinarily obtain their carbohydrate supply from the carbon dioxide in the air by the process of photosynthesis. Each of these nutrients is used in a different place for a different essential function.[6]

Macronutrients (derived from air and water).

Carbon.

Carbon forms the backbone of most plant biomolecules, including proteins, starches and cellulose. Carbon is fixed through photosynthesis; this converts carbon dioxide from the air into carbohydrates which are used to store and transport energy within the plant.

Hydrogen.

Hydrogen is necessary for building sugars and building the plant. It is obtained almost entirely from water. Hydrogen ions are imperative for a proton gradient to help drive the electron transport chain in photosynthesis and for respiration.[5]

Oxygen.

Oxygen is a component of many organic and inorganic molecules within the plant, and is acquired in many forms. These include: O2 and CO2 (mainly from the air via leaves) and H2O, NO− 3, H2PO− 4 and SO2− 4 (mainly from the soil water via roots). Plants produce oxygen gas (O2) along with glucose during photosynthesis but then require O2 to undergo aerobic cellular respiration and break down this glucose to produce ATP.

Macronutrients (primary).

Further information: Microbial inoculant

Nitrogen.

Further information: Nitrogen cycle

Nitrogen is a major constituent of several of the most important plant substances. For example, nitrogen compounds comprise 40% to 50% of the dry matter of protoplasm, and it is a constituent of amino acids, the building blocks of proteins.[7] It is also an essential constituent of chlorophyll.[8] Nitrogen deficiency most often results in stunted growth, slow growth, and chlorosis. Nitrogen deficient plants will also exhibit a purple appearance on the stems, petioles and underside of leaves from an accumulation of anthocyanin pigments.[5] Most of the nitrogen taken up by plants is from the soil in the forms of NO− 3, although in acid environments such as boreal forests where nitrification is less likely to occur, ammonium NH+ 4 is more likely to be the dominating source of nitrogen.[9] Amino acids and proteins can only be built from NH+ 4, so NO− 3 must be reduced. In many agricultural settings, nitrogen is the limiting nutrient for rapid growth. Nitrogen is transported via the xylem from the roots to the leaf canopy as nitrate ions, or in an organic form, such as amino acids or amides. Nitrogen can also be transported in the phloem sap as amides, amino acids and ureides; it is therefore mobile within the plant, and the older leaves exhibit chlorosis and necrosis earlier than the younger leaves.[5][8]

There is an abundant supply of nitrogen in the earth's atmosphere — N2 gas comprises nearly 79% of air. However, N2 is unavailable for use by most organisms because there is a triple bond between the two nitrogen atoms in the molecule, making it almost inert. In order for nitrogen to be used for growth it must be “fixed” (combined) in the form of ammonium (NH+ 4) or nitrate (NO− 3) ions. The weathering of rocks releases these ions so slowly that it has a negligible effect on the availability of fixed nitrogen. Therefore, nitrogen is often the limiting factor for growth and biomass production in all environments where there is a suitable climate and availability of water to support life.

Nitrogen enters the plant largely through the roots. A “pool” of soluble nitrogen accumulates. Its composition within a species varies widely depending on several factors, including day length, time of day, night temperatures, nutrient deficiencies, and nutrient imbalance. Short day length promotes asparagine formation, whereas glutamine is produced under long day regimes. Darkness favors protein breakdown accompanied by high asparagine accumulation. Night temperature modifies the effects due to night length, and soluble nitrogen tends to accumulate owing to retarded synthesis and breakdown of proteins. Low night temperature conserves glutamine; high night temperature increases accumulation of asparagine because of breakdown. Deficiency of K accentuates differences between long- and short-day plants. The pool of soluble nitrogen is much smaller than in well-nourished plants when N and P are deficient since uptake of nitrate and further reduction and conversion of N to organic forms is restricted more than is protein synthesis. Deficiencies of Ca, K, and S affect the conversion of organic N to protein more than uptake and reduction. The size of the pool of soluble N is no guide per se to growth rate, but the size of the pool in relation to total N might be a useful ratio in this regard. Nitrogen availability in the rooting medium also affects the size and structure of tracheids formed in the long lateral roots of white spruce (Krasowski and Owens 1999).[10]

Microorganisms have a central role in almost all aspects of nitrogen availability, and therefore for life support on earth. Some bacteria can convert N2 into ammonia by the process termed nitrogen fixation; these bacteria are either free-living or form symbiotic associations with plants or other organisms (e.g., termites, protozoa), while other bacteria bring about transformations of ammonia to nitrate, and of nitrate to N2 or other nitrogen gases. Many bacteria and fungi degrade organic matter, releasing fixed nitrogen for reuse by other organisms. All these processes contribute to the nitrogen cycle.

Phosphorus.

Further information: Phosphorus cycle

Like nitrogen, phosphorus is involved with many vital plant processes. Within a plant, it is present mainly as a structural component of the nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), as well as a constituent of fatty phospholipids, that are important in membrane development and function. It is present in both organic and inorganic forms, both of which are readily translocated within the plant. All energy transfers in the cell are critically dependent on phosphorus. As with all living things, phosphorus is part of the Adenosine triphosphate (ATP), which is of immediate use in all processes that require energy with the cells. Phosphorus can also be used to modify the activity of various enzymes by phosphorylation, and is used for cell signaling. Phosphorus is concentrated at the most actively growing points of a plant and stored within seeds in anticipation of their germination. Phosphorus is most commonly found in the soil in the form of polyprotic phosphoric acid (H3PO4), but is taken up most readily in the form of H2PO− 4. Phosphorus is available to plants in limited quantities in most soils because it is released very slowly from insoluble phosphates and is rapidly fixed once again. Under most environmental conditions it is the element that limits growth because of this constriction and due to its high demand by plants and microorganisms. Plants can increase phosphorus uptake by a mutualism with mycorrhiza.[5] A Phosphorus deficiency in plants is characterized by an intense green coloration or reddening in leaves due to lack of chlorophyll. If the plant is experiencing high phosphorus deficiencies the leaves may become denatured and show signs of death. Occasionally the leaves may appear purple from an accumulation of anthocyanin. Because phosphorus is a mobile nutrient, older leaves will show the first signs of deficiency.

On some soils, the phosphorus nutrition of some conifers, including the spruces, depends on the ability of mycorrhizae to take up, and make soil phosphorus available to the tree, hitherto unobtainable to the non-mycorrhizal root. Seedling white spruce, greenhouse-grown in sand testing negative for phosphorus, were very small and purple for many months until spontaneous mycorrhizal inoculation, the effect of which was manifested by a greening of foliage and the development of vigorous shoot growth.

Phosphorus deficiency can produce symptoms similar to those of nitrogen deficiency,[11] but as noted by Russel:[12] “Phosphate deficiency differs from nitrogen deficiency in being extremely difficult to diagnose, and crops can be suffering from extreme starvation without there being any obvious signs that lack of phosphate is the cause”. Russell's observation applies to at least some coniferous seedlings, but Benzian[13] found that although response to phosphorus in very acid forest tree nurseries in England was consistently high, no species (including Sitka spruce) showed any visible symptom of deficiency other than a slight lack of lustre. Phosphorus levels have to be exceedingly low before visible symptoms appear in such seedlings. In sand culture at 0 ppm phosphorus, white spruce seedlings were very small and tinted deep purple; at 0.62 ppm, only the smallest seedlings were deep purple; at 6.2 ppm, the seedlings were of good size and color.[14][15]

It is useful to apply a high phosphorus content fertilizer, such as bone meal, to perennials to help with successful root formation.[5]

Potassium.

Unlike other major elements, potassium does not enter into the composition of any of the important plant constituents involved in metabolism,[7] but it does occur in all parts of plants in substantial amounts. It seems to be of particular importance in leaves and at growing points. Potassium is outstanding among the nutrient elements for its mobility and solubility within plant tissues. Processes involving potassium include the formation of carbohydrates and proteins, the regulation of internal plant moisture, as a catalyst and condensing agent of complex substances, as an accelerator of enzyme action, and as contributor to photosynthesis, especially under low light intensity.

Potassium regulates the opening and closing of the stomata by a potassium ion pump. Since stomata are important in water regulation, potassium regulates water loss from the leaves and increases drought tolerance. Potassium deficiency may cause necrosis or interveinal chlorosis. The potassium ion (K+) is highly mobile and can aid in balancing the anion (negative) charges within the plant. Potassium helps in fruit coloration, shape and also increases its brix. Hence, quality fruits are produced in potassium-rich soils. Potassium serves as an activator of enzymes used in photosynthesis and respiration.[5] Potassium is used to build cellulose and aids in photosynthesis by the formation of a chlorophyll precursor. Potassium deficiency may result in higher risk of pathogens, wilting, chlorosis, brown spotting, and higher chances of damage from frost and heat.

When soil-potassium levels are high, plants take up more potassium than needed for healthy growth. The term luxury consumption has been applied to this. When potassium is moderately deficient, the effects first appear in the older tissues, and from there progress towards the growing points. Acute deficiency severely affects growing points, and die-back commonly occurs. Symptoms of potassium deficiency in white spruce include: browning and death of needles (chlorosis); reduced growth in height and diameter; impaired retention of needles; and reduced needle length.[16] A relationship between potassium nutrition and cold resistance has been found in several tree species, including two species of spruce.[17]

Macronutrients (secondary and tertiary).

Sulfur.

Sulfur is a structural component of some amino acids (including cystein and methionine) and vitamins, and is essential for chloroplast growth and function; it is found in the iron-sulfur complexes of the electron transport chains in photosynthesis. It is needed for N2 fixation by legumes, and the conversion of nitrate into amino acids and then into protein.[18]

In plants, sulfur cannot be mobilized from older leaves for new growth, so deficiency symptoms are seen in the youngest tissues first.[19] Symptoms of deficiency include yellowing of leaves and stunted growth.[20]

Calcium.

Calcium regulates transport of other nutrients into the plant and is also involved in the activation of certain plant enzymes. Calcium deficiency results in stunting. This nutrient is involved in photosynthesis and plant structure.[21][22] Blossom end rot is also a result of inadequate calcium.[21]

Another common symptom of calcium deficiency in leaves is the curling of the leaf towards the veins or center of the leaf. Many times this can also have a blackened appearance[23] Calcium has been found to have a positive effect in combating salinity in soils. It has been shown to ameliorate the negative effects that salinity has such as reduced water usage of plants.[24] Calcium in plants occurs chiefly in the leaves, with lower concentrations in seeds, fruits, and roots. A major function is as a constituent of cell walls. When coupled with certain acidic compounds of the jelly-like pectins of the middle lamella, calcium forms an insoluble salt. It is also intimately involved in meristems, and is particularly important in root development, with roles in cell division, cell elongation, and the detoxification of hydrogen ions. Other functions attributed to calcium are; the neutralization of organic acids; inhibition of some potassium-activated ions; and a role in nitrogen absorption. A notable feature of calcium-deficient plants is a defective root system.[12] Roots are usually affected before above-ground parts.[25]

Magnesium.

Main article: Magnesium in biological systems

The outstanding role of magnesium in plant nutrition is as a constituent of the chlorophyll molecule. As a carrier, it is also involved in numerous enzyme reactions as an effective activator, in which it is closely associated with energy-supplying phosphorus compounds. Magnesium is very mobile in plants, and, like potassium, when deficient is translocated from older to younger tissues, so that signs of deficiency appear first on the oldest tissues and then spread progressively to younger tissues.

Micro-nutrients.

Plants are able sufficiently to accumulate most trace elements. Some plants are sensitive indicators of the chemical environment in which they grow (Dunn 1991),[26] and some plants have barrier mechanisms that exclude or limit the uptake of a particular element or ion species, e.g., alder twigs commonly accumulate molybdenum but not arsenic, whereas the reverse is true of spruce bark (Dunn 1991).[26] Otherwise, a plant can integrate the geochemical signature of the soil mass permeated by its root system together with the contained groundwaters. Sampling is facilitated by the tendency of many elements to accumulate in tissues at the plant's extremities.

Iron.

Iron is necessary for photosynthesis and is present as an enzyme cofactor in plants. Iron deficiency can result in interveinal chlorosis and necrosis. Iron is not a structural part of chlorophyll but very much essential for its synthesis. Copper deficiency can be responsible for promoting an iron deficiency.[27] It helps in the electron transport of plant.

Molybdenum.

Molybdenum is a cofactor to enzymes important in building amino acids and is involved in nitrogen metabolism. Molybdenum is part of the nitrate reductase enzyme (needed for the reduction of nitrate) and the nitrogenase enzyme (required for biological nitrogen fixation).[8] Reduced productivity as a result of molybdenum deficiency is usually associated with the reduced activity of one or more of these enzymes.

Boron.

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Boron is absorbed by plants in the form of the anion BO3− 3. It is available to plants in moderately soluble mineral forms of Ca, Mg and Na borates and the highly soluble form of organic compounds. It is available to plants over a range of pH, from 5.0 to 7.5. It is mobile in the soil, hence, it is prone to leaching. Leaching removes substantial amounts of boron in sandy soil, but little in fine silt or clay soil. Boron's fixation to those minerals at high pH can render boron unavailable, while low pH frees the fixed boron, leaving it prone to leaching in wet climates. It precipitates with other minerals in the form of borax in which form it was first used over 400 years ago as a soil supplement. Decomposition of organic material causes boron to be deposited in the topmost soil layer. When soil dries it can cause a precipitous drop in the availability of boron to plants as the plants cannot draw nutrients from that desiccated layer. Hence, boron deficiency diseases appear in dry weather.

Boron has many functions within a plant: it affects flowering and fruiting, pollen germination, cell division, and active salt absorption. The metabolism of amino acids and proteins, carbohydrates, calcium, and water are strongly affected by boron. Many of those listed functions may be embodied by its function in moving the highly polar sugars through cell membranes by reducing their polarity and hence the energy needed to pass the sugar. If sugar cannot pass to the fastest growing parts rapidly enough, those parts die.

Boron is not relocatable in the plant via the phloem. It must be supplied to the growing parts via the xylem. Foliar sprays affect only those parts sprayed, which may be insufficient for the fastest growing parts, and is very temporary.

Boron is essential for the proper forming and strengthening of cell walls. Lack of boron results in short thick cells producing stunted fruiting bodies and roots. Calcium to boron ratio must be maintained in a narrow range for normal plant growth. For alfalfa, that calcium to boron ratio must be from 80:1 to 600:1. Boron deficiency appears at 800:1 and higher. Boron levels within plants differ with plant species and range from 2.3 mg/kg for barley to 94.7 mg/kg for poppy. Lack of boron causes failure of calcium metabolism which produces hollow heart in beets and peanuts.

Inadequate amounts of boron affect many agricultural crops, legume forage crops most strongly. Of the micronutrients, boron deficiencies are second most common after zinc. Deficiency results in the death of the terminal growing points and stunted growth.

Boron supplements derive from dry lake bed deposits such as those in Death Valley, USA, in the form of sodium tetraborate (borax), from which less soluble calcium borate is made. Foliar sprays are used on fruit crop trees in soils of high alkalinity. Boron is often applied to fields as a contaminant in other soil amendments but is not generally adequate to make up the rate of loss by cropping. The rates of application of borate to produce an adequate alfalfa crop range from 15 pounds per acre for a sandy-silt, acidic soil of low organic matter, to 60 pounds per acre for a soil with high organic matter, high cation exchange capacity and high pH.

Boron concentration in soil water solution higher than one ppm is toxic to most plants. Toxic concentrations within plants are 10 to 50 ppm for small grains and 200 ppm in boron-tolerant crops such as sugar beets, rutabaga, cucumbers, and conifers. Toxic soil conditions are generally limited to arid regions or can be caused by underground borax deposits in contact with water or volcanic gases dissolved in percolating water. Application rates should be limited to a few pounds per acre in a test plot to determine if boron is needed generally. Otherwise, testing for boron levels in plant material is required to determine remedies. Excess boron can be removed by irrigation and assisted by application of elemental sulfur to lower the pH and increase boron solubility.

Boron deficiencies can be detected by analysis of plant material to apply a correction before the obvious symptoms appear, after which it is too late to prevent crop loss. Strawberries deficient in boron will produce lumpy fruit; apricots will not blossom or, if they do, will not fruit or will drop their fruit depending on the level of boron deficit. Broadcast of boron supplements is effective and long term; a foliar spray is immediate but must be repeated.

Copper.

Copper is important for photosynthesis. Symptoms for copper deficiency include chlorosis. It is involved in many enzyme processes; necessary for proper photosynthesis; involved in the manufacture of lignin (cell walls) and involved in grain production. It is also hard to find in some soil conditions.

Manganese.

Manganese is necessary for photosynthesis,[22] including the building of chloroplasts. Manganese deficiency may result in coloration abnormalities, such as discolored spots on the foliage.

Sodium.

Sodium is involved in the regeneration of phosphoenolpyruvate in CAM and C4 plants. Sodium can potentially replace potassium's regulation of stomatal opening and closing.[5]

Essentiality of sodium:

·         Essential for C4 plants rather C3

·         Substitution of K by Na: Plants can be classified into four groups:

1.      Group A—a high proportion of K can be replaced by Na and stimulate the growth, which cannot be achieved by the application of K

2.      Group B—specific growth responses to Na are observed but they are much less distinct

3.      Group C—Only minor substitution is possible and Na has no effect

4.      Group D—No substitution occurs

·         Stimulate the growth—increase leaf area and stomata. Improves the water balance

·         Na functions in metabolism

1.      C4 metabolism

2.      Impair the conversion of pyruvate to phosphoenol-pyruvate

3.      Reduce the photosystem II activity and ultrastructural changes in mesophyll chloroplast

·         Replacing K functions

1.      Internal osmoticum

2.      Stomatal function

3.      Photosynthesis

4.      Counteraction in long distance transport

5.      Enzyme activation

·         Improves the crop quality e.g. improves the taste of carrots by increasing sucrose

Zinc.

Zinc is required in a large number of enzymes and plays an essential role in DNA transcription. A typical symptom of zinc deficiency is the stunted growth of leaves, commonly known as "little leaf" and is caused by the oxidative degradation of the growth hormone auxin.

Nickel.

In higher plants, nickel is absorbed by plants in the form of Ni2+ ion. Nickel is essential for activation of urease, an enzyme involved with nitrogen metabolism that is required to process urea. Without nickel, toxic levels of urea accumulate, leading to the formation of necrotic lesions. In lower plants, nickel activates several enzymes involved in a variety of processes, and can substitute for zinc and iron as a cofactor in some enzymes.[2]

Chlorine.

Chlorine, as compounded chloride, is necessary for osmosis and ionic balance; it also plays a role in photosynthesis.

Cobalt.

Cobalt has proven to be beneficial to at least some plants although it does not appear to be essential for most species.[28] It has, however, been shown to be essential for nitrogen fixation by the nitrogen-fixing bacteria associated with legumes and other plants.[28]

Aluminum.

Aluminum is one of the few elements capable of making soil more acidic. This is achieved by aluminum taking hydroxide ions out of water, leaving hydrogen ions behind.[29] As a result, the soil is more acidic, which makes it unlivable for many plants. Another consequence of aluminum in soils is aluminum toxicity, which inhibits root growth.[30]

·         Tea has a high tolerance for aluminum (Al) toxicity and the growth is stimulated by Al application. The possible reason is the prevention of Cu, Mn or P toxicity effects.

·         There have been reports that Al may serve as a fungicide against certain types of root rot.

Silicon.

Silicon is not considered an essential element for plant growth and development. It is always found in abundance in the environment and hence if needed it is available. It is found in the structures of plants and improves the health of plants.[31]

In plants, silicon has been shown in experiments to strengthen cell walls, improve plant strength, health, and productivity.[32] There have been studies showing evidence of silicon improving drought and frost resistance, decreasing lodging potential and boosting the plant's natural pest and disease fighting systems.[33] Silicon has also been shown to improve plant vigor and physiology by improving root mass and density, and increasing above ground plant biomass and crop yields.[32] Silicon is currently under consideration by the Association of American Plant Food Control Officials (AAPFCO) for elevation to the status of a "plant beneficial substance".[34][35]

Vanadium.

Vanadium may be required by some plants, but at very low concentrations. It may also be substituting for molybdenum.

Selenium.

Selenium is probably not essential for flowering plants, but it can be beneficial; it can stimulate plant growth, improve tolerance of oxidative stress, and increase resistance to pathogens and herbivory.[36]

Selenium is, however, an essential mineral element for animal (including human) nutrition and selenium deficiencies are known to occur when food or animal feed is grown on selenium-deficient soils. The use of inorganic selenium fertilizers can increase selenium concentrations in edible crops and animal diets thereby improving animal health.[36]

Nutrient deficiency.

The effect of a nutrient deficiency can vary from a subtle depression of growth rate to obvious stunting, deformity, discoloration, distress, and even death. Visual symptoms distinctive enough to be useful in identifying a deficiency are rare. Most deficiencies are multiple and moderate. However, while a deficiency is seldom that of a single nutrient, nitrogen is commonly the nutrient in shortest supply.

Chlorosis of foliage is not always due to mineral nutrient deficiency. Solarization can produce superficially similar effects, though mineral deficiency tends to cause premature defoliation, whereas solarization does not, nor does solarization depress nitrogen concentration.[37]

Researchers found that partial deficiencies of K or P did not change the fatty acid composition of phosphatidyl choline in Brassica napus L. plants. Calcium deficiency did, on the other hand, lead to a marked decline of polyunsaturated compounds that would be expected to have negative impacts for integrity of the plant membrane, that could effect some properties like its permeability, and is needed for the ion uptake activity of the root membranes.[38]

Nutrient status of plants.

Nutrient status (mineral nutrient and trace element composition, also called ionome and nutrient profile) of plants are commonly portrayed by tissue elementary analysis. Interpretation of the results of such studies, however, has been controversial.[39] During recent decades the nearly two-century-old “law of minimum” or “Liebig's law” (that states that plant growth is controlled not by the total amount of resources available, but by the scarcest resource) has been replaced by several mathematical approaches that use different models in order to take the interactions between the individual nutrients into account.

Later developments in this field were based on the fact that the nutrient elements (and compounds) do not act independently from each other;[39] Baxter, 2015,[40] because there may be direct chemical interactions between them or they may influence each other's uptake, translocation, and biological action via a number of mechanisms[39] as exemplified[how?] for the case of ammonia.[41]

Plant nutrition in agricultural systems.

Hydroponics.

Hydroponics is a method for growing plants in a water-nutrient solution without the use of nutrient-rich soil. It allows researchers and home gardeners to grow their plants in a controlled environment. The most common solution is the Hoagland solution, developed by D. R. Hoagland and W. C. Snyder in 1933. The solution (known as A-Z solution) consists of all the essential nutrients in the correct proportions necessary for most plant growth.[5] An aerator is used to prevent an anoxic event or hypoxia. Hypoxia can affect nutrient uptake of a plant because, without oxygen present, respiration becomes inhibited within the root cells. The nutrient film technique is a hydroponic technique in which the roots are not fully submerged. This allows for adequate aeration of the roots, while a "film" thin layer of nutrient-rich water is pumped through the system to provide nutrients and water to the plant.

 

 

How are coastal farmers responding to salty soils?

BYSUSTAINABLESECUREFOODBLOG

When most people think about agricultural fields, they envision vast landscapes of crops as far as the eye can see. Although that may be true for parts of the Midwest, it’s a very different story on the Eastern Shore in Maryland.

Here, the line is blurred between farmland and marshland. What was once land where corn grew along the edges of agricultural fields is now home to wetlands with plants like salt marsh hay.

What have these changes taken place – at the whim of Mother Nature? Why is the marsh migrating onto coastal farmlands? The short answer – saltwater intrusion.

Salt-intruded farm field in Somerset County, Maryland. This farm is next to a marsh and brackish tributary; both provide unwanted salts to the farm field. Photo credit: Jarrod Miller

Saltwater intrusion, the movement of sea salts from coasts to inland locations, is driven by several things:

1. Well-known rising sea levels.
2. Withdrawal of water from coastal aquifers for human use.
3. The increased frequency and duration of droughts.
4. The connections among agricultural water ditches.
5. The frequency of storms and tides.

Although soil salinization is not a new issue facing farmlands, saltwater intrusion is. This unique phenomenon is comprised of high salinity levels and long periods of saturation. This causes problems for farmers in coastal areas.

An actively managed farm field, which is growing soybean this season, in Somerset County, Maryland that is experiencing saltwater intrusion. In the foreground, salt marsh hay is growing and in the background an invasive weed species growing. The extensive bare area where nothing is growing has some of the highest salt concentrations on the field. Photo credit: Elizabeth de la Reguera

High soil salinity does not allow a productive and profitable rotation of corn, soy, and wheat, common crops along the Eastern Shore of Maryland. These crops can only tolerate salty soils up to a point – and that point was reached years ago. Currently, there is about 5 times more salt in the soils than corn, soy or wheat can tolerate!

Salt stress can reduce a plant’s ability to absorb water. So, even though water might be present, the crops can’t easily access it – it’s like they are experiencing a drought. Saline soils also can cause ion imbalances. You might be familiar with electrolyte solutions used for long-distance runners. The balance in these solutions is important – the correct amount of sodium, magnesium and calcium is important for athletes, and even “regular” humans.

It’s the same for plants, too. These ion imbalances can suppress growth and limit productivity. The worse-case scenario is plant death. Farmers face a tough decision – try to continue farming, restore the land to wetland, or abandon their fields and way of life.

Corn attempting to grow on a salt-intruded farm field there is currently inundated with saltwater. Photo credit: Kate Tully

Farmers who wish to continue farming have started replacing crops with salt-tolerant species. For example, farmers have switched to sorghum because corn is no longer producing profitable yields. Farmers have also switched varieties of soy, because some are more salt-tolerant than others. Some types of barley can grow in our region, too.

Part of my research is determining the correct rotations of these new crops for farmers.  Our preliminary data shows that salt-tolerant soybean has a higher percent germination compared to sorghum on salt-intruded farm fields.

When we investigated reasons why the sorghum wasn’t doing well, we found some interesting things. The sorghum wasn’t germinating well. Most likely, sorghum is more sensitive to sodium and chloride toxicity. We found other reasons that affected the salt-tolerant soy. This helps us make recommendations to farmers. However, the differences in each crops’ sensitivity to different stressors associated with saltwater intrusion highlights the complexity and challenges for these farmers, and the scientists who support them.

In some cases, the only decision for a coastal farmer is to abandon their farm fields and put them into different uses. When a farmer stops planting crops, we have found a unique community of agricultural weeds and wetland species takes over the land. This suggests that abandoned fields may facilitate marsh migration.

So, whether a farmer chooses to switch to a salt-tolerant cropping system or abandon their field, the marsh is still going to encroach onto the fields.

University of Maryland field trial on a salt-intruded field. Investigating sorghum, salt-tolerant soybean, salt marsh hay, and switchgrass for salt tolerance. Photo credit: Jarrod Miller

Further, as weather conditions become variable (i.e. frequency in storms and droughts) and sea level continues to rise, saltwater intrusion will only move further inland. But what if a farmer decided to restore their salt-intruded field to a tidal wetland instead of surrendering to nature? Farmers can enroll in the Conservation Reserve Enhancement Program (CREP) to take their farmland out of production for at least a decade and establish wetlands. This provides farmers with an income and provides ecosystem services. For example, agricultural soils are very low in carbon compared to tidal wetland soils. Thus, converting the land to a tidal wetland has the potential to store carbon now and sequester more carbon in the future, which can help mitigate climate change.

At the end of the day, a farmer needs to decide what the best course of action is for them. The unfortunate reality is that we can’t stop saltwater intrusion. In a decade or two, these farmlands will more closely resemble a tidal wetland than an agricultural field. H

 

What do nutrients do for plants?

If a plant decided to go on a diet, you know, to keep its plant-like figure, what do you think it would choose to be as healthy as possible?

It turns out that plants, like humans, rely on essential nutrients to maintain a healthy and balanced lifestyle. So, what’s the plant equivalent of a protein shake you might be wondering?

Probably an N-P-K shake comprised mostly of nutrients like nitrogen (N), phosphorus (P), and potassium (K). Then you can add some “shots” of smaller amounts of calcium (Ca), magnesium (Mg), and sulfur (S), which are essential for plant health.

A comparison of common nutrients and what they do for plants and humans. Source: Agronomy: Grow with It!, Ateh et al., 2016, page 73.

Nitrogen (N)

Nitrogen is used by plants to create amino acids, the building blocks of proteins. Proteins are essential for all our human and plant cells. Amino acids are needed to form protoplasm – the site for cell division. That makes nitrogen crucial to plant growth and development. All plant enzymes used in biochemical reactions are also made of proteins.

Besides the creation of amino acids and proteins, nitrogen is also a necessary component of the chlorophyll molecule. So, nitrogen influences the photosynthesis process. Nitrogen can improve the quality and quantity of dry matter in leafy vegetables and protein in grain crops. Nitrogen deficiency results in stunted growth, pale green or yellowing of older leaves, as the plant tries to scavenge nitrogen from older leaves to younger tissues.

You might be thinking, well I’m going to pour on the fertilizer, but hold that thought! Plants can also have toxic levels of a nutrient. Nitrogen toxicity also results in stunted growth with plants looking dark green. It can also result in vegetative bud formation (more plant leaves or stems), instead of reproductive bud formation (more flowers or crops), which isn’t very good for yield.

Phosphorus (P)

Another big player in plant nutrition is phosphorus. It is very important in plant metabolism. Phosphorus is used in plant photosynthesis and respiration as it is needed for energy storage and transfer. It’s also part of RNA and DNA, the stores of genetic information of living things. Seeds usually have large stores of phosphorus available for young cells in shoot and root tips where growth is rapid. If the plant lacks phosphorus, this would result in stunted growth as cell division gets compromised. Luckily, phosphorus can be mobilized in a plant and transferred to sites of new growth. However, if a plant does this, it causes older leaves to appear dark or blue-green, even purple in severe cases. Phosphorus deficiency thus causes slow development and low seed and fruit quality. But be cautious about applying too much phosphorus to a plant – excess amounts can cause iron and zinc deficiencies.

Potassium (K)

Potassium is a bit different to nitrogen and phosphorus. It doesn’t become part of any organic compounds in the plant. It’s more like the ultimate assistant to many processes happening in a healthy growing plant. For example, potassium assists in the regulation of water use in the plant by controlling the opening and closing of stomata, allowing the plant to cool itself. At sites of energy production, potassium maintains the balance of electrical charge. Potassium has even been shown to improve disease resistance of the plant, improve the size of seeds and grains and improve quality of fruits and vegetables. But too much potassium can also result in toxic levels in the plant leading to calcium, magnesium and nitrogen deficiencies.

Calcium (Ca)

Calcium is needed in smaller amounts in the plant but it’s not mobile in the plant. This means that if adequate amounts of calcium aren’t available, symptoms of deficiency will first appear on young leaves as growth is stunted. Growing points of the stem and roots also stop developing with notable deterioration of the root system before the above-ground parts of the plant. Again, on the flip side, high calcium in a plant can cause magnesium and boron deficiencies.

Magnesium deficiency in a canola plant leaf. Notice the vein area remains green, while the rest of the leaf is turning yellow. Credit: Ivan Izgagin

Magnesium (Mg)

Magnesium is an important component of the chlorophyll molecule and therefore needed for photosynthesis. It is mobile in the plant, therefore when there’s a deficiency, chlorosis first occurs on older leaves in the leaf tissue between the leaf veins. Leaves can start to look yellow, bronze or reddish while leaf veins remain green. High magnesium levels can cause a calcium deficiency.

Sulfur (S)

Finally, sulfur is used by the plant to create some amino acids and is essential for chloroplast growth and function (the part of the cell where photosynthesis occurs). Sulfur is not mobilized in a plant so symptoms of deficiency first show on new plant growth where there is a uniform yellowing of new plant tissue. Growth is stunted and maturity is delayed which lowers yield. Toxic levels of sulfur are hard to create so a plant likely won’t suffer from this problem.

PIB’S DAILY BULLETIN ON COVID-19

 

                         PIB’S DAILY BULLETIN ON COVID-19

Posted On: 01 OCT 2020 6:23PM by PIB Delhi

 

(Contains Press releases concerning Covid-19, issued in last 24 hours, inputs from PIB Field Offices and Fact checks undertaken by PIB)

 

India sustains trend of consistent low level of Active Cases, For the 10th successive day, Active Cases below 10 lakh mark, India's total Recoveries nearly 53 lakh, The last 10 lakh recoveries added in just 12 days

India has sustained its trend of maintaining the active cases below the 10 lakh mark. For the 10^th successive day, the active cases are less than 1 million (10 lakhs). With a very high number of COVID patients recovering every single day, India’s steady trend of posting high level of daily recoveries also continues. 85,376 recoveries have been registered in the last 24 hours in the country. India’s total recoveries stands at 52,73,201 today. Higher number of single day recoveries have resulted in continuous increase in the national recovery rate, which is currently pegged at 83.53%. The rise in total recovered cases has been steep. The last 10 lakh recoveries were added in just 12 days. 77% of the total recovered cases are recorded in 10 States/UTs. Maharashtra has contributed the highest number to the total recovered cases followed by Andhra Pradesh and Tamil Nadu. The active cases in India are 9,40,705. India reported 9.4 lakh active cases earlier on 11^th September, 2020. 76% of the active cases are in 10 States/UTs. As on date, the active cases contribute only 14.90% to the positive caseload of the country.  A total of 86,821 new confirmed cases have been reported in the last 24 hours in the country. 76% of the new cases are concentrated in ten states. Maharashtra contributed more than 18,000 to the new cases. Karnataka and Kerala, both contributed more than 8,000. 1,181 deaths have been registered in the past 24 hours. 82% of new deaths are reported from 10 States and UTs.  40% of deaths reported yesterday are from Maharashtra with 481 deaths followed by Karnataka with 87 deaths.

For details :

A lot is done but more focused and collective action needed for mitigation of Air pollution: Shri Prakash Javadekar

 

                         A lot is done but more focused and collective action needed for mitigation of Air pollution: Shri Prakash Javadekar

Trial of ICAR developed biodecomposer technology to be done in NCR and neighboring states this year.

Posted On: 01 OCT 2020 4:59PM by PIB Delhi

Environment, Forest and Climate Change Minsiter, Shri Prakash Javadekar today chaired a review meeting on the situation of air pollution which has been a recurrent environmental concern in winter season in Northern India especially in Delhi NCR region over last few years. Five states Delhi, Uttar Pradesh, Haryana, Rajasthan and Punjab particpated in the meeting.

In a press briefing after the meeting which lasted for more than 90 minutes,Shri Javadekar said, that the meeting was fruitful in addressing the issue and that centre and state have worked and will work together to implement steps to combat air pollution, but more needs to be done.

In an effort to combat air pollution caused due to stubble burning the Minister informed that the centre has allotted a fund of Rs. 1700 crore to the states for stubble management. Currently,80% subsidy to cooperatives and 50% subsidy to individuals on machineries for stubble is being provided to curb pollution caused due to stubble burning.

The Minister stated that Hotspots have been identified in states of UP, Haryana and Rajasthan too and the state governments have been directed to pay more attention to these. State action plans have been made and discussed which will be implemented. Union minister emphasized that Delhi government has been directed to take more action on the 13 hotspots in Delhi so as to reduce the air pollution in the capital. 50 teams of CPCB will be deployed in Delhi NCR region to take appropriate action this year.

He further added that the trial of Pusa Microbial Decomposer Capsule is underway in Delhi NCR and informed that Uttar Pradesh will be using this technology over an area of 10,000 hectrares this year and Delhi will be using the same for 800 hectares as informed by Environment Ministers of these states during the meeting.Union Minister Prakash Javadekar also stated the importance of using Bio Decomposers, Bio CNG and Bio power to reduce air pollution and its negative impact.

The minister emphasised that there are several other factors that contribute to air pollution other than stubble burning which include constructions and demolition waste, poor waste management, unpaved roads and  dust management, Bio mass burning, etc. Today,States have shared their plans to fight against pollution and the Centre have suggested more steps to deal with it further.

The minister informed that several measures have been taken by the centre like BS VI norms have been introduced; power plants of Badarpur have Sonipat have been closed. He stated that Eastern and Western Peripheral Expressways have helped massively in reducing vehicular air pollution in Delhi and nearly 60,000 vehicles are diverted from Delhi which earlier used to go through Delhi.

To conclude the minister appealed to the state governments as well as the masses to also take constructive measures to contribute in reducing air pollution and informed that the Central Pollution Control Board will work actively with all states on a daily basis to monitor the level of pollution. 

However, COVID-19 has also shown that Nature can still be conserved, restored and used sustainably.

 

Ministry of Environment, Forest and Climate Change

Urgent need to accelerate action to conserve biodiversity: India at UN Biodiversity Summit

Posted On: 01 OCT 2020 7:11PM by PIB Delhi

Representing India at the United Nations(UN) Biodiversity Summit on the occasion of 75^th anniversary of the UN General Assembly, Union Minister for Environment, Forest and Climate Change, Shri Prakash Javadekar, said that as we are approaching the end of the UN Decade on Biodiversity 2011-2020 there is an urgent need to accelerate action to conserve biodiversity.  

The summit is first of its kind ever taken place on Biodiversity in the United Nations General Assembly. The Biodiversity Summit was participated by Head of States/Minister level representing the countries which are party to Convention on Biological Diversity (CBD). The Union Environment addressed the summit virtually.

The full text of the Environment Minister’s address is as follows:-

 

Excellencies, Ladies and Gentlemen,

• I stand before this august gathering to address the 75^th Session of the United Nations General Assembly as a representative of one of the seventeen mega-bio-diverse countries in the world.

 

• Since time immemorial, India has a culture of not just conserving and protecting nature, but living in harmony with nature.

 

• The emergence of COVID-19 has emphasized the fact that un-regulated exploitation of natural resources coupled with un-sustainable food habits and consumption pattern lead to destruction of system that supports human life.

 

• However, COVID-19 has also shown that Nature can still be conserved, restored and used sustainably.

 

• As we are approaching the end of the UN Decade on Biodiversity 2011-2020 there is an urgent need to accelerate action to conserve biodiversity.

 

Excellencies,

• As enshrined in our Vedic scripts “PrakritiRakshatiRakshita” that is if you protect nature, nature will protect you.

 

• Inspired by Mahatma Gandhi, the ethos of non-violence and protection of animals and nature have been suitably enshrined in the Constitution of India and is reflected in several laws and legislations.

 

• It is due to these beliefs and ethos that India, with only 2.4% of the earth’s land area hosts around 8% of the world’s recorded species.

 

• I am happy to inform this august gathering that in the course of last decade, India has enhanced the combined forest and tree cover to 24.56% of the total geographical area of the country.

 

• We now have the highest number of tigers in the wild and have doubled its numbers ahead of the deadline of 2022and recently announced the launch of Project Lion and Project Dolphin.

 

• India aims to restore 26 million hectares of degraded and deforested land, and achieve land-degradation neutrality by 2030.

 

• India has already set aside extensive area for meeting the conservation objectives, contributing to Aichi Biodiversity Target-11 and the SDG -15.

 

• India has established a comprehensive institutional and legal system to realize the objectives of the Convention on Biological Diversity (CBD).

 

• India has operationalized a system for access and benefit-sharing provisions of the CBD through a national network of 0.25 million Biodiversity Management Committees across the country involving local people and 0.17 million Peoples Biodiversity Registers for documentation of biodiversity.

 

Excellencies,

 

• The post-2020 global biodiversity framework that will be adopted at the 15^th Conference of Parties to the CBD in 2021 provides a good opportunity to enhance efforts to conserve and protect nature.

 

• India has already taken leadership role in order to conserve biodiversity by organizing two Conference of Parties(CoPs) within a span of less than a year

 

• We organized CoP-14 of UNCCD during September, 2019 in New Delhi, followed by CoP 13 of the Convention on Migratory Species (CMS) in Gandhinagar in Gujarat during February 2020.

 

• India has been championing the cause of “climate action” through conservation, sustainable lifestyle and green development model.

 

Excellencies,

On the occasion of the “75^th anniversary of the UN” and the start of the “UN Decade of Action and Delivery for Sustainable Development”, lets join our efforts to put nature on a path to recovery and realize the vision of “living in harmony with nature”.

 

 

I thank you.

 

***

GK

 

(Release ID: 1660746) Visitor Counter : 29

Salient Features of Monsoon 2020

                         Salient Features of Monsoon 2020

the all India seasonal rainfall this year was third highest, after 112% of LPA in 1994 and 110% of LPA in 2019

Out of 36 meteorological subdivisions, 2 subdivisions received large excess, 13 received excess and 16 subdivisions received normal monsoon rainfall during 2020 while only 5 subdivisions received deficient rainfall

Monsoon in 2020 withdrew from western parts of northwest India on 28th Sept. 2020 against the normal date of 17th Sept 2020 with a delay of around 11-days.

The cool ENSO neutral conditions observed over the equatorial Pacific Ocean in the beginning of the year turned in to weak La Niña conditions by the end of August 2020 as predicted by IMD

Posted On: 01 OCT 2020 4:17PM by PIB Delhi

The India Meteorological Department (IMD) has issued the following information on India Monsoon 2020:

Ø Quantitatively, the 2020 All India monsoon seasonal rainfall during 1 June to 30 September 2020 has been 95.8 cm against the long period average of 88.0 cm based on data of 1961-2010 (109% of its Long Period Average (LPA)).

Ø Considering the recent years since 1990, the all India seasonal rainfall this year was third highest, after 112% of LPA in 1994 and 110% of LPA in 2019.

Ø Thus 2019 & 2020 are the two consecutive years with above normal monsoon rainfall, after 1958 (110% of LPA) and 1959 (114% of LPA ) (Fig.1).

Ø Considering four broad homogenous regions of India, the monsoon seasonal rainfall during 2020 has been 106%, 84%, 115% & 129% of LPA respectively over East and North-East(NE), North- West(NW), Central and South India. Therefore, seasonal rainfall has been excess over Central and South India, normal over East and NE India and deficient over NW India. Monthly and seasonal total rainfall over different broad homogeneous regions and all India are given in Fig. 2.

Ø Out of 36 meteorological subdivisions, 2 subdivisions received large excess, 13 received excess and 16 subdivisions received normal monsoon rainfall during 2020 while only 5 subdivisions received deficient rainfall (Fig. 3). These 5 Met subdivisions which got deficient rains are Nagaland, Manipur, Mizoram & Tripura (- 32%), West Uttar Pradesh (-37%), Uttarakhand (-20%), Himachal Pradesh        (- 26%), Jammu & Kashmir and Ladakh (-34%) (Fig. 3).

Ø Considering month to month rainfall variation over India as a whole, the season is very uniquely placed in the historical record for its distinct and contrasting month to month variation. The rainfall over country as a whole was 118%, 90%, 127% and 104% of LPA during June, July, August and September respectively (Fig 2).

The spatial distribution of monthly rainfall over different Met- Subdivisions is shown in Fig 4.

Ø The week to week progress of monsoon rainfall over country as a whole and cumulative rainfall in percentage departure is shown in Fig. 5

Ø It was a good beginning for the season in terms of rainfall with formation and movement of the cyclone Nisarga, over the Arabian Sea. It helped the monsoon to advance into main-land along the west coast. Subsequent features favored timely advance and monsoon covered entire country by 26th 2 June against normal date of 8th July (about 12 days ahead of normal date). The country as a whole experienced excess rainfall (118% of LPA) during June.

Ø In July, many unfavorable features of monsoon appeared resulting in deficient rainfall for the country (90% of LPA). The weak monsoon in July was mainly due to absence of any major monsoon disturbance over Bay of Bengal. Absence of such major systems in July (Table 1) also caused the monsoon trough weak. The monsoon trough lay to the north of the normal position or closed to the foothills of the Himalayas on many days. It resulted in frequent and prolonged floods over northeastern India, Bihar and adjoining areas of east Uttar Pradesh.

At the same time, major parts of central and northwest India received deficient rainfall.

Ø During August, there was back to back formation of low pressure systems over the north Bay of Bengal and their movement towards Gujarat and south Rajasthan (Table 1). Monsoon trough was mostly south of the normal position and remained active. Arabian Sea was very active with stronger winds reaching up to 50-60kmph in lower levels during a few days in the month. Five low pressure systems formed during 4-10 , 9-11, 13-18 , 19-26 and 24-31 August 2020 which caused higher than normal rainfall over central and western part of India. Total number of low pressure days was 28 against normal of about 17(Table 1). It caused 2-3 spells of riverine floods over Odisha, Telangana, Madhya Pradesh, south Gujarat and south Rajasthan. It was a record rainfall in August 2020, when all India rainfall was 127% of LPA. It has been the record highest in last 44- years, after August 1976 (128.4% of LPA). It is also fourth highest in last 120 years. The highest ever percentage departure for the month of August during 1901-2020 had been 33% above LPA during 1926. The all India rainfall in percentage departure from LPA for the month of the August during 1901-2020 is shown in Fig.6.

Ø During August 2020, consecutively for 4 weeks, India got excess rain with 13% to 41% above LPA during week ending 12 Aug to week ending 2 Sept 2020. Similarly, the most deficient monsoon conditions prevailed in second fortnight of July.

Ø Month-wise locations of Very Heavy Rainfall (115.6 to 204.4 mm) and Extremely Heavy Rainfall (more than 204.4 mm) reported stations for June to Sept 2020 given in Fig 7.

Ø Monsoon in 2020 withdrew from western parts of northwest India on 28th Sept. 2020 against the normal date of 17th Sept 2020 with a delay of around 11-days. Withdrawal has been delayed mainly due to active monsoon trough in association with the formation of 2 low pressure systems in Sept 2020.

Ø As on 01st October, southwest monsoon has withdrawn from Punjab, western Himalayan region,

Haryana, Chandigarh, Delhi and many parts for Rajasthan and some parts of Uttar Pradesh. The withdrawal line of the Southwest Monsoon passes through Lat. 29°N/ Long.81°E, Lakhimpur Kheri, Shahjhanpur, Alwar, Nagaur and Lat. 26°N/ Long.70°E.

Verification of Long Range Forecast:

Ø The forecast for the date of monsoon Onset Over Kerala issued on 15th May 2020 was 5th June with a model error of ±4 days. The actual monsoon onset over Kerala was on 1st June and therefore the forecast was correct.

Ø The first stage forecast for the season (June-September) rainfall over the country as a whole issued in April was 100% of LPA with a model error of ± 5% of LPA. The forecast was upgraded to 102% of LPA with a model error of ± 4% of LPA in the updated forecast issued in May. IMD also predicted a probability of 65% of monsoon rainfall to be normal to above normal. However, the actual seasonal rainfall for the country as a whole was 109% of LPA, which is more than the predicted value.

Ø Considering the four broad geographical regions of India, the forecasts issued in May for the season 3 rainfall over Northwest India, Central India, Northeast India and South Peninsula were 107%, 103%, 96% & 102% of the LPA respectively all with model errors of ± 8%. The actual rainfall over Northwest India, Central India, Northeast India and South Peninsula was 84%, 115%, 107% and 129% of the LPA respectively. Thus, the forecasts of season rainfall over the Central India, Northeast India and South Peninsula regions were underestimate to the actual rainfall, while the forecast for Northwest India was an overestimate. The forecast for the second half of the monsoon season (August – September) for the country as a whole was 104% with a model error of 8% of LPA against the actual rainfall of 118% of LPA.

Ø This year, IMD had predicted possibility of the development of weak La Nina conditions in the second half of the season in its forecasts issued in April and May. The cool ENSO neutral conditions

observed over the equatorial Pacific Ocean in the beginning of the year turned in to weak La Niña conditions by the end of August 2020 as predicted by IMD.

CLICK HERE FOR--  (For Fig 1 to Fig 7, refer Page 4 to 8 and for Table 1, refer Page 9)