Major Elements

Major elements must be readily available as they are usually lacking from the soil as plants consume large amounts for their growth and survival.

Nitrogen is an essential element in all living cells and is a necessary part of all proteins, enzymes and metabolic processes involved in the synthesis and transfer of energy.It is an important component of chlorophyll, the green pigment in leaves of plants, and plays a significant part in determining their yield and quality. Nitrogen facilitates rapid growth of plants, increasing seed, flower and fruit production. Plants adequately supplied with nitrogen are lush green and vigorous.Nitrogen Deficiency Symptoms:

  • Light greenish to yellowish colour (more pronounced in older leaves)
  • Stunted growth
  • Lower leaves appear scorched and show dominance of orange or red pigments.
  • Low yields and low protein content of grain, pasture and forage.

Phosphorous like nitrogen, is closely concerned with many important processes within the plant. It is part of nucleic acids, and therefore an essential part of all living cells.Plants require a ready supply of phosphorous at all stages of growth, but especially in the early stages of growth. It is of special importance during germination of seeds, root development and the ripening process of seeds and fruit.It stimulates early root development, leaf size, tillering, green formation and hastens maturity.Phosphorous is essential for nodulation and successful growth in legumes.Phosphorous Deficiency Symptoms:

  • Poor root development
  • Stunted growth
  • Spindly stalks
  • Reduced tillering
  • Delayed maturity
  • Purplish discolouration in older leaves
  • Poor fruit and seed development

Potassium plays an important role in almost all functions of plant development, grain and seed formation.Potassium aids in the following processes:

  • Photosynthesis
  • Reduces respiration
  • Essential for protein formation
  • Aids many enzyme actions
  • Helps to transport sugar and starches
  • Helps cells to maintain their internal pressure and reduces wilting
  • Increases root growth and drought resistance
  • Helps control water absorption through plant pores
  • Reduces lodging
  • Increases disease resistance
  • Regulates vegetative growth
  • Increases grain and fruit size
  • Aids in longer storage of fruit and vegetables

Potassium Deficiency Symptoms:

  • Plants grow slowly
  • Stalks weaken and lodge easily
  • Seed and fruits shrivel
  • White and yellow spots develop along the margin of leaves (legumes)
  • Moisture stress and drought symptoms appear quickly and are more pronounced

Calcium is necessary for the proper function of growing points, being a permanent part of the cell walls, particularly in the root tips. It plays an important role in the metabolism of nitrogen. Calcium is relatively immobile in the plant and therefore a constant supply should be made available during the period of vegetative growth. Calcium deficiencies are usually quite rare.Calcium Deficiency Symptoms:

  • In extreme cases it can be known to cause empty shells in groundnuts
  • Low calcium in conjunction with low phosphorous availability, results in stunted root growth in plants

Magnesium is part of the chlorophyll formation and is an important part of the process, converting sunlight into a usable energy source.Magnesium has a key role in phosphorous transport and is particularly important in the formation of seed.Magnesium also plays a significant role in the exchange capacity of the three main cations – K, Mg and Ca, since the plant under dominance of one of these elements can take up any of those cations which is available in abundance at the expense of the other element, not as freely available. Excess K applications can induce Mg deficiency symptoms.Magnesium Deficiency Symptoms:

  • Contrary to N deficiency where the whole leaf yellows, with Mg the veins remain green while the intervenial areas become orange yellow. This most pronounced on leaves exposed to sunlight
  • Leaves become abnormally thin
  • In oil producing crops, reduction in oil content is common
  • In cotton, leaves develop a purplish-red colour between the green veins
  • Low Mg can affect the uptake and transport within the plant of P, therefore a suspected P symptom could relate to low Mg availability

 

Trace Elements

Trace elements must be available to plants for normal healthy growth, even though they are necessary only in small amounts.

Chlorophyll formation and several plant enzymes rely on copper. It is also needed for reproductive growth, aid in root metabolism and in the utilisation of proteins. Copper should only be applied in small amounts as it can be highly toxic when present in soils in appreciable quantities available to plants.Copper Deficiency Symptoms:

  • In cereals it may show up through leaf distortion and “tip burn”
  • In maize it causes yellowing between leaf veins
  • In vegetables it causes die back of leaves
  • In general, plants appear “bleached”, roots and tops are stunted

Zinc is involved in several enzymes systems and is essential for protein synthesis.Zinc is responsible for regulating plant growth rate and development. It also plays a regulatory role in the transformation of carbohydrates, consumption of sugars, intake and efficient use of water by the plant.Zinc Deficiency Symptoms:

  • Stunted growth
  • Chlorosis – usually white
  • Early loss of foliage

Boron is important in the plant for cell division and metabolism, protein synthesis, pollen viability, flower and fruit formation and ultimately the yield.It is most important in quality of fruits and vegetables.Boron Deficiency Symptoms:

  • In maize and sorghum – white stripe between leaf veins, flower and cob sterility
  • Cotton – excessive shedding of squares and bolls
  • In legumes – internodes near growing points shorten, plants become stunted
  • Root crops – splitting and discolouration in the thickening part of the root – “heart rot”
  • Vegetables – hollow stems, stunting and deformities in young plants
  • Fruit trees – die back of terminal twigs, heavy fruit shedding

Iron is essential for formation of chlorophyll and is active in the oxidation process, releasing energy from sugar and starches.Iron Deficiency Symptoms:

  • Usually chlorosis – whitening of the young leaves – veins remain green

Manganese has several functions in the plant and is closely associated with iron, copper and zinc as a catalyst in the plants growth process.
Chlorophyll production, carbohydrate and nitrogen metabolism also depend upon Manganese.Manganese Deficiency Symptoms

  • Intervenial yellowing of young leaves, followed by spots of dead tissue which may drop out giving the leaf a ragged appearance.

Generally Mo is the least abundant trace element in soils and generally very little is present in forms available for plants. Only minute quantities are required by the plant. Mo is needed by plants to aid in the use of nitrogen nutrition.Molybdenum Deficiency Symptoms:

  • Symptoms similar to those of nitrogen deficiency
  • Failure of leaves to develop healthy green colour
  • Stunted plants
  • Yellowing of the tissue on the outer of leaves
  • Leaf edges will start to curl upwards
  • Intervenial and marginal leaf chlorosis followed by death along leaf margins

The Role of Fertiliser Nutrients