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In order for plants to grow, they need 13 mineral nutrient elements and other non mineral nutrients. The elements which are required for a plant to complete it's life cyle are called essential plant nutrients and vary in amount from element to element.
'Macronutrients' are plant nutrients required in the largest amount in plants whilst 'Micronutrients' are required in relatively smaller amounts. Additional mineral nutrient elements which are beneficial to plants but not necessarily essential include sodium, cobalt, vanadium, nickel, selenium, aluminum and silicon.
Nutrient elements differ in many forms. By their form, the way they are absorbed by plants, function in a plant and mobility in plant etc.
Macronutrients tend to be less available in soils with low pH whilst micronutrients tend to be less available in soils with high pH.
Although Boron is only present in plants as a trace element, it is important to reduce features like brittle stems, dying growing tips, and hollow stems in brassicas.
Deficiency: Death of growing points and deformation of leaves with areas of discoloration.
Excess: Leaf tips become yellow followed by necrosis. Leaves get a scorched appearance and later fall off.
Essential part of plant cell wall structure, provides for normal transport and retention of other elements as well as strength in the plant. It is also thought to counteract the effect of alkali salts and organic acids within a plant.
Deficiency: Reduced growth or death of growing tips; blossom-end rot of tomato; poor fruit development and appearance.
Excess: May cause deficiency in either magnesium or potassium.
Activates photosynthetic enzymes.
Deficiency: Very rare, but causes leaves to wilt and change in colour from green through to yellow, eventually becoming a bronze colour.
Excess: Leaves wilt. They may appear translucent brown with a soft, jelly-like consistency. Leaves darken/brown on the edge. Plant does not flower.
Important for reproductive growth.
Deficiency: Stunted with very small terminal leaves. Terminal leaves eventually die and multiple budding occurs immediately below the dead terminal. These buds will also die and often multiple buds will develop on each break making it look like broomstick like.
Excess: Symptoms appear in young tissue and include; dark green leaves followed by induced Fe chlorosis in which the leaves may appear nearly white; thick, short, or barbed-wire looking roots which can be mistaken for chemical damage; depressed tillering.
Essential for formation of chlorophyll.
Deficiency: Initial distinct yellow or white areas between veins of young leaves leading to spots of dead leaf tissue.
Excess: Possible bronzing of leaves with tiny brown spots.
Part of chlorophyll. Activates many enzymes.
Deficiency: Initial yellowing of older leaves between leaf veins spreading to younger leaves; poor fruit development and production.
Excess: High concentration tolerated in plant; however, imbalance with calcium and potassium may reduce growth.
Formation of amino acids. Electron carries catalyst.
Deficiency: Interveinal yellowing or mottling of young leaves.
Excess Older leaves have brown spots surrounded by a chlorotic circle or zone.
Necessary in both plant and animal nutrition.Soil pH is the major soil factor affecting the availability of molybdenum to plants. Generally, if the pH is 6.0 or higher, a deficiency will not occur.
Deficiency: Leaf edges curl upward on the whole plant. Causes "whip-tail" in cauliflowers, and "blossom end rot" in tomatoes.
Excess: Rare in plants but leaves turn intense yellow or purple color.
Nitrogen is important for many functions of a plant. It is available to gardeners in two forms: ammonia-type nitrogen and nitrate-type nitrogen. Most plants prefer to obtain their nitrogen in the nitrate form. Urea and Sulphate of Ammonia are unsuitable for hydroponics as they need to undergo conversion from ammonia-type to nitrate-type by soil bacteria before plants can use them. In sunny climates, plants need more nitrogen than the same plants in a cooler climate. Plants such as lettuce, cabbage and silverbeet generally need more nitrogen than less leafy plants. The most popular nitrate-type fertilizers are Potassium Nitrate and Calcium Nitrate.
Deficiency: Light green to yellow appearance of leaves, especially older leaves; stunted growth; poor fruit development.
Excess: Dark green foliage which may be susceptible to lodging, drought, disease and insect invasion. Fruit and seed crops may fail to yield.
All plants require phosphorus during periods of rapid growth. Most annual plants (plants that grow, reproduce,and die in one year) require large amounts of phosphorus as they begin to grow. Plants grown in cold weather which have limited roots and rapid top growth, suchas lettuce, are high phosphorususers. Legumes also require plentiful amounts of phosphorus. Established plants such as trees, shrubs and vines, especially those grown in warm climates with long summers, require the least amounts of phosphorus fertilizer.
Deficiency: Less growth than you would expect. Shoots thin and an upright habit. Leaves paler than usual with forward roll and scorched margins; defoliation of oldest leaves. Leaves can turn purple.
Excess: May cause micronutrient deficiencies, especially iron or zinc.
All plants require potassium,especially crops high in carbohydrates,such as potatoes.Studies have shown that adequate amounts of potassiummay promote the growth of long, strong cotton fibers; increase the shelf life of fruits; increase the stem length and quantity of roses; enhance the green color and growth of turf grass;and increase the size and quality of fruits, grains, and vegetables.
Deficiency: Older leaves turn yellow initially around margins and die; irregular fruit development.
Excess: May cause deficiencies in magnesium and possibly calcium.
Sulphur is a building block of proteins, enzymes and vitamins and is a key ingredient in the formation of chlorophyll.
Deficiency: Stunted or tall spindly growth. Initial yellowing of younger leaves spreading to whole plant; similar symptoms to nitrogen deficiency but instead of occuring on established leaves, occurs generally on new growth. Reduced amount of seed or crops.
Excess: May cause premature dropping of leaves.
Zinc is another element present in trace quantity. It acts as chemical catalysts, assisting other elements to do their job.
Deficiency: Interveinal yellowing on young leaves; reduced leaf size.
Excess: May cause iron deficiency in some plants.
Non Mineral Nutrients
The non-mineral nutrients which plants need to grow are Hydrogen (H), Oxygen (O), & Carbon (C). They are found in both air and water.
Plants use energy from the sun (Photosynthesis) to change carbon dioxide (CO2 - carbon and oxygen) and water (H2O- hydrogen and oxygen) into starches and sugars. These starches and sugars become food for the plant.