THE PLANT NUTRIENTSMacro NutrientsCarbon (C) Used in exceptionally large quantitiesHydrogen (H)Oxygen (O)Nitrogen (N) Used in large quantitiesPhosphorus (P)Potassium (K)Secondary NutrientsCalcium (Ca)Magnesium (Mg) Used in moderate quantitiesSulfur (S)MicronutrientsBoron (B)Chlorine (Cl)Cobalt (Co)Copper (Cu)Iron (Fe)Manganese (Mn) Used in small quantitiesMolybdenum (Mo)Nickel (Ni)Silicon (Si)Sodium (Na)Zinc (Zn)Vanadium (Va)Carbon, Hydrogen and Oxygen represent 90-96% of the dry matter of all plants. Theseelements are supplied by atmospheric carbon dioxide and water. The plant obtains theremaining 4-10% from the soil and/or fertiliser inputs.
A more detailed table listing approximate concentrations of nutrient elements required forhealthy plant growth is as follows. Concentration in dry matter Element ppm % Hydrogen 60 000 6.0 Carbon 420 000 42.0 Oxygen 480 000 48.0 Nitrogen 14 000 1.4 Potassium 10 000 1.0 Calcium 5 000 0.5 Magnesium 2 000 0.2 Phosphorus 2 000 0.2 Sulfur 1 000 0.1 Chlorine 100 Iron 100 Boron 20 Manganese 50 Zinc 20 Copper 6 Molybdenum 0.1 Sodium trace Cobalt trace Silicon trace*Edwards D.G. (1971) Concepts of essentiality and function of nutrientsIn commercial agriculture the following elements are applied, when necessary, to improvecrops. Macronutrients Secondary Nutrients Micronutrients Nitrogen (N) Calcium (Ca) Zinc (Zn) Iron (Fe) Phosphorus (P) Magnesium (Mg) Manganese (Mn) Copper (Cu) Potassium (K) Sulfur (S) Boron (B) Molybdenum (Mo)
NUTRIENT FUNCTIONS IN THE DEFICIENCY SYMPTOMS CONDITIONS THAT SENSITIVE PLANT REDUCE AVAILABILTY CROPS • an essential element in all • lighter green or yellow coloured light or sandy soils where All crops are sensitive to living systems leaves (first evident in older leaves) nitrate nitrogen is leached nitrogen deficiency • needed by all cells – some plants eg. berries can water logged soils Nitrogen • occurs in the living develop red or orange colours soils with structural problems (N) substance (protoplasm) of • stunted growth lower protein levels in pasture and as a result of poor aeration mineral soils low in organic cells • • a major component of grain matter protein • delayed maturity soils where nitrogen has been • a major component of • decreased resistance to disease depleted by previous crops chlorophyll which converts and/or insect attack soils where the ammonium sunlight into plant energy • smaller fruit form has been applied to high • affects both yields and • lower yields pH soils (free ammonia) quality. • shorter storage life • necessary for proper cell • reduced growth – sometimes soil with a pH less than 5.5 or Cereals, maize, broccoli, division and the formation of stunted and other times only more than 7.0 cabbage, cucumber, new cells evident from shortened internodes, soil with a high clay content lettuce, potatoes, softPhosphorus • photosynthesis smaller leaves and reduced shoot mineral soils low in organic fruits, tree fruits (P) • sugar and starch formation • growth. dark green colour in some crops matter soil with high levels of hydrous (particularly citrus) and tomatoes. • energy transfer • carbohydrate transport. • purple leaves in others eg. oxides of aluminum or iron brassicas soils where phosphorus has • reduced tillering in cereals been depleted by previous • small misshapen fruit – can be crops pulpy with poor storage life • poor seed development
NUTRIENT FUNCTIONS IN THE DEFICIENCY SYMPTOMS CONDITIONS THAT SENSITIVE PLANT REDUCE AVAILABILTY CROPS • aids photosynthesis and the • light green to yellow older leaves continuously cropped soils with Apples, beans, berries, functioning of chlorophyll which later develop marginal leaf low levels of organic matter broccoli, citrus, cucurbits, • important for the formation scorch- different plants have their soils without balanced fertiliser grapes, legumes, lettuce, and translocation of own visual deficiency symptoms programs maize, nuts, passionfruit, starches, sugars and fats • plant growth is retarded light sandy soils where peas, potatoes, rhubarb,Potassium potassium has been leached stone fruit, sunflowers, • involved in protein formation • lodging (K) • aids many enzyme actions • disease resistance is reduced periods of drought prolonged periods of heavy rain tomatoes. • helps cells maintain their • stalks are weakened internal pressure • seed and fruit is misshapen some clay soils (eg. • reduces wilting and Krasnozems) respiration by maintaining soils in which deficiencies of the balance of salts and phosphorus and molybdenum water in cells have been corrected • improves crop quality heavily limed soil soils formed from parent • increases root growth and material low in potassium resistance to disease and drought • decreases lodging. necessary for the proper terminal buds and root tips fail to • low pH soils. Tree crops, fruit and functioning of growing develop normally. • where there is an unfavourable vegetables. points particularly root tips • lodging balance of calcium, magnesium forms compounds which • stunted root systems and potassium in the soil Calcium is not easily strenghten cell walls • leaves of grasses do not open (particularly heavy potassium translocated in plants, so Calcium aids in cell division and properly the tips of which stick to inputs in sandy soils) a constant supply is elongation the next lowest leaf where high rates of nitrogen required. This should be (Ca) neutralises organic acids • soft fruit • have been used foliar applied and in aids in the proper working • senescent breakdown and poor fruiting crops be available and permeability of cell storage life of fruit from after flowering membranes • internal and external disorders of onwards. regulates protein synthesis many fruit and vegetables and slows the aging process.
NUTRIENT FUNCTIONS IN THE DEFICIENCY SYMPTOMS CONDITIONS THAT SENSITIVE PLANT REDUCE AVAILABILTY CROPS the only mineral constituent • interveinal chlorosis beginning in • sandy acid soils – particularly in Vines, pome fruit, stone of the chlorophyll molecule the tips of older leaves. Veins high rainfall areas fruit, citrus, maize, aids plants to form sugars remain green, the chlorotic areas • course textured soils in humid tomatoes, capsicums,Magnesium and starches change from yellow to brown (other regions broccoli, cauliflower, plays an important part in colours in some plants). • cold wet conditions lettuce, potatoes, parsley, (M) the translocation of • leaves become brittle and necrotic • soils where there have been pumpkin and many phosphorus and may drop prematurely heavy inputs of potassium others. aids several plant enzymes • yield can be seriously reduced • soils which have received to function. • cotton leaves develop a purplish – repeated green manuring red colour between green veins • some varieties of black grapes and stone and pit fruit can develop interveinal red chlorotic areas • grass tetany in sheep and cattle • excessive premature fruit drop similar requirements to • generally very similar to nitrogen soils low in organic matter that Cotton, clovers, phalaris, phosphorus in plants deficiency - a uniform pale green to have been cropped for many barrel medic, lucerne, a constituant of several yellow leaf but the difference is years. canola, wheat, barley, Sulfur amino acids which are sulfur deficiency starts in the new maize, sunflowers, essential for protein leaves whereas nitrogen deficiency acid sandy soils where sulphate soybean, navy beans, (S) production starts in the old leaves. has been leached - especially sorghum, oats and aids the activities of some • In legumes the nodules produced such areas with high winter triticale. are smaller, pale rather than pink rainfall. enzymes and vitamins needed for chlorophyll and reduced in number formation • deficiencies in field crops include deficiency adversely affects poor low yielding plants, low the oil content in some oil protein and pale green and yellow crops and the baking quality leaves in wheat. in wheat crops aids efficient nitrogen stabilisation needed for nodule formation in legumes
NUTRIENT FUNCTIONS IN THE DEFICIENCY SYMPTOMS CONDITIONS THAT SENSITIVE PLANT REDUCE AVAILABILTY CROPS plays a role in cell division, • thick, curled and brittle tissues – high pH soils Cotton, barley, maize, aids efficient translocation cracking and splitting, sometimes overlimed soils oats, sorghum,Boron of calcium, with gumosis soils with high levels of nitrogen sunflower, clover, (B) protein synthesis, carbohydrate metabolism, • surfaces of leaf, petioles, stems and midribs develop cracks or a and/or calcium sandy soils that are easily lucerne, navy beans, soy beans, citrus, nuts, pome pollen viability corky appearance leached fruit, stone fruit, root flower and fruit set and • reduced flowering, seed set and soils with low organic content crops and vegetables. formation. fruit set. cold wet weather (especially Hormone formation • Growth points can die forming following a long dry spell) multiple side shoots • Small misshapen fruit • Internal flesh disorders and cracking in fruit and vegetables required for chlorophyll • marginal chlorosis of young leaves soils with excess nitrogen Cereals, maize, lucerne, production sometimes necrotic tips (if severe) and/or phosphorus citrus trees, carrots, helps with photosynthesis • twig dieback high pH soils lettuce and onions aids in the production of • sometimes necrotic and brown heavily limed soils enzyme protein spots over leaf surface soils that have had Copper involved in several enzyme molybdenum applied • reduced growth and yields (Cu) systems involved in several oxidation peat and muck soils – high in organic matter reduction reactions and the leached acid soils formation of lignins alkaline and calcarious soils helps regulate water cold wet conditions (availability movement in plants. can often be delayed at spring Required for seed time) production soils with high concentrations of iron and manganese soils formed from parent materials low in copper
NUTRIENT FUNCTIONS IN THE DEFICIENCY SYMPTOMS CONDITIONS THAT SENSITIVE PLANT REDUCE AVAILABILTY CROPS necessary for the formation • young leaves – interveinal high pH soils Vines, fruit crops, stone of chlorophyll chlorosis with green veins after heavy liming fruits, citrus, vegetables, aids in photosynthesis • later in season – yellowing of soils with high levels of metallic field peas, beans and Iron involved in the oxidation leaves (margins and tips can ions cereals process that releases scorch) poorly drained and/or aerated (Fe) energy from starches and • stunted growth soils enzymes • reduced yield and quality soils with high levels of copper aids in the formation of soils with low potassium levels proteins especially when associated involved in the conversion with high potassium levels of nitrate to ammonia in the plant. aids respiration. essential for chlorophyll • chlorosis of recently matured high pH soils Citrus, pome fruit, stone production and leaves with no reduction in leaf limed soils fruit, vines, strawberries, photosynthesis. size light sandy soils tomatoes, potatoes,Manganese aids nitrogen and • less pronounced mottling in some soils low in potassium legumes, vegetables, carbohydrate metabolism broad leaf plants soils low in organic matter cereals (especially oats), (Mn) oxidation reduction • small grains can show a soil high in copper, iron and sorgham involved in the activity of longitudinal striping zinc several enzymes • “grey fleck” in oats cold wet periods combines with copper, iron • chlorosis in citrus (more evident on soils that have evolved from and zinc to aid plant growth the shady side of the tree parent materials low in processes. manganese
NUTRIENT FUNCTIONS IN THE DEFICIENCY SYMPTOMS CONDITIONS THAT SENSITIVE PLANT REDUCE AVAILABILTY CROPS is a co-factor in the enzyme • in general similar to nitrogen low pH soils – particularly if Cucurbits (cucumbers, nitrate-reductose deficiency - yellowing or pale they contain aluminium and/or melons etc.) aids in the conversion of leaves, stunting, necrotic leaf iron oxides Crucifers (cabbage,Molybdenum nitrates of ammonium (the margins and tips (this is because soils with high copper levels canola, cauliflower etc.) initial stage of synthesis of without molybdenum plants cannot soils with low phosphate levels Legumes (beans, (Mo) proteins) metabolise nitrogen) – symptoms soils derived from parent lucerne, peas, soya essential for Rhyzobia to start in older leaves first materials low in molybdenum beans etc.) enable legume crops to fix • flowers can wither or be aerobic (atmospheric) suppressed nitrogen helps plants to utilise nitrate nitrogen involved in phosphate and iron metabolism necessary for the formation • stunted growth soils evolved from parent Cereals, cotton, fruit, pip of chlorophyll • leaves reduced in size and material low in zinc and citrus trees, nuts, Zinc involved in several enzyme misshapen high pH soils and soils heavily oilseed crops, pome fruit, systems, the growth limed rice, stone fruit, (Zn) hormone auxins and the • chlorosis (leaf mottling) leading to necrosis and premature leaf fall clay soils with high magnesium vegetables. synthesis of nucleic acids • chlorotic leaves and dieback in levels plays a part in the intake citrus soils high in organic matter and use of water in by • rosetting and/or “little leaf” in fruit soils high in potassium plants. trees soils that have been leveled, • “tram lining” – light striping both exposing the sub-soils sides of the midrib- in maize soils that have had high • bronze spotting on older leaves nitrogen inputs later giving a mottled appearance cold wet conditions (availability in legumes can often be delayed at spring time) • reduced development and size of fruit
NUTRIENT MOBILITYNutrient mobility in soilVery Mobile – (prone to leaching)nitrate Nitrogen, sulfate Sulfur, BoronModerately Mobile –ammonium Nitrogen ( ammonium Nitrogen is temporarily immobile),Potassium, Calcium, Magnesium, MolybdenumImmobile –organic Nitrogen, Phosphorus, Copper, Iron, Manganese, Zinc(Chelated forms of Copper, Iron, Manganese and Zinc are mobile andresistant to leaching)Nutrient mobility in plantsVery mobile –Nitrogen, Phosphorus, Potassium, Magnesium(Deficiency symptoms appear first in older leaves and quickly spreadthroughout the plant)Moderately mobile –Sulfur, Copper, Iron, Manganese, Molybdenum, Zinc(Deficiency symptoms first appear in new growth but do not readilytranslocate to old growth)Immobile –Boron, Calcium(Calcium is very immobile)
NUTRIENT ANTAGONISM AND INTERACTIONNITROGENWhen high levels of Nitrogen induce accelerated growth rates, levels of micronutrients thatwould normally be marginal can become deficient.High soil levels of Nitrogen can assist Phosphorus, Calcium, Boron, Iron and Zinc but anexcess can dilute these elements.Low soil levels can reduce Phosphorus, Calcium, Boron, Iron and Zinc uptake.Ammonium Nitrogen can make Molybdenum deficiency appear less obvious.PHOSPHORUSHigh levels of Phosphorus reduce Zinc and, to a lesser degree, Calcium uptake. It isantagonistic to Boron in low pH soils.POTASSIUMHigh levels of Potassium reduce Magnesium and to lesser extent Calcium, Iron, Copper,Manganese and Zinc uptake. Boron levels can either be low or toxic.Low levels can accentuate Iron deficiency.CALCIUMHigh levels of Calcium can accentuate Boron deficiency. Liming can decrease the uptake ofBoron, Copper, Iron, Manganese and Zinc by raising soil pH.COPPERHigh levels of Copper can accentuate Molybdenum and to a lesser degree Iron, Manganeseand Zinc deficiency.IRONIron deficiency can be accentuated by limimg, low Potassium levels or high levels of Copper,Manganese or Zinc.MANGANESEHigh levels of Copper, Iron or Zinc can accentuate Manganese deficiency – especiallyrepeated soil applications of Iron. Uptake can be decreased by liming or increased by Sulfurapplications (because of the affects on pH)
MOLYBDENUMDeficiencies can be accentuated by high levels of Copper and to a lesser degreeMnaganese. Uptake can be adversely affected by sulfates. Uptake can be increased byphosphates and liming.Molybdenum can increase Copper deficiencies in animals.ZINCUptake can be decreased by high Phosphorus levels, liming or high levels of Copper, Iron orManganese. Zinc deficiencies are often associated with Manganese deficiencies, especiallyin citrus.
EFFECT OF SOIL REACTION ON AVAILABILITY OF NUTRIENTSThe availability of nutrients at specific pH ranges differs between mineral and organic soils.The following charts demonstrate these differences.Influence of pH on the availability of plant nutrients in mineral soils; wildest parts of the shaded areas indicate maximum availability of eachelementAdapted from L.B.Nelson (Ed.) Changing Patterns in Fertiliser Use, Soil Science Society America, Madison,WI (1968).Influence of pH on the availability of plant nutrients in organic soils; widest parts of the shaded areas indicate maximum availability of eachelement.Adapted from E.E. Lucas and J.F. Davis. Relationships between pH values of organic soils and availability of 12 plant nutrients, SoilScience 92:177-182 (1961)