• Why is it important to me as a farmer?
• Why do we need trace elements?
• How to recognise the need for trace elements in the paddock

• Managing the application of trace elements

• Comparatively small amounts of micronutrients such as copper (Cu), zinc (Zn), manganese (Mn), iron (Fe), molybdenum (Mo), boron (B) and chloride (Cl) are required compared to macronutrients such as nitrogen, phosphorus, potassium, sulphur or carbon
• Chemical interactions can occur with trace minerals that reduce their availability and cause deficiencies, even when there is sufficient nutrient in the soil

• Although only required in small amounts, minor nutrients (micronutrients or trace elements) are essential for plant growth
• These nutrients often act as catalysts in chemical reactions. It is possible to have toxicities of trace elements, as well as deficiencies

• Sixteen nutrients are known to be essential for plant growth. They can be divided into two categories:
  • Major nutrients (macronutrients)
  • Minor nutrients (micronutrients), often referred to as trace elements

• The first three major nutrients, carbon, hydrogen and oxygen, are generally considered to come from carbon dioxide in the atmosphere and from water. Combined, they make up 90% to 95% of the dry matter of all plants
• The remaining nutrients are found in the soil and are taken up through the root system of the plant. However, legumes (such as clovers, lucerne and medics) also have the ability to convert atmospheric nitrogen into a plant-available form
• Comparatively smaller amounts of micronutrients such as copper (Cu), zinc (Zn), manganese (Mn), iron (Fe), molybdenum (Mo), boron (B) and chloride (Cl) are required
• Selenium (Se) is an essential element for animals, but not plants
• The need for micronutrient application is largely determined by soil conditions and processes such as soil acidity, fixation and leaching
• Micronutrients are normally present in soil in small quantities only and deficiencies may occur due to seasonal conditions or other nutrients limiting uptake
• Some Australian soils are naturally deficient in trace elements and it is likely that these deficiencies may become more significant in the future following the intensification of production systems, but it is relatively easy and cheap to overcome
• The term trace elements applies to elements, in addition to the micronutrients, that are present in soil in small concentrations � some of these can be toxic to plants

• Soil tests are usually not reliable to determine the status of available trace minerals in the soil
• Visual symptoms can be used as a guide to trace mineral deficiencies. Plant tissue and animal sample tests are useful to confirm most trace mineral deficiencies

• Molybdenum (Mo)
  • Essential for the health of the rhizobia bacteria associated with the legume root nodules that are responsible for atmospheric nitrogen fixation. It is also directly involved in nitrogen metabolism and specifically implicated in the electrontransfer system (for example, nitrate reductase and enzyme nitrogenous reactions). Molybdenum is the least abundant of the trace elements in the soil
  • Molybdenum deficiency symptoms may look similar to a nitrogen deficiency, and legumes will have green or grey to white nodules rather than the pinkish-coloured nodules of healthy plants
  • Consequently, a lack of molybdenum will reduce the nitrogen-fixing ability and growth of clovers. In effect, molybdenum-deficient plants cannot properly metabolise nitrogen, even though their tissues may contain considerable amounts of nitrates

• Copper (Cu)
  • Required for the formation of enzymes for chlorophyll production, nutrient processing and the plant�s exchange of water and oxygen for carbon dioxide. It is also required for seed setting of legumes. Plant responses (in other words, additional growth) due to copper are rare
  • Copper deficiency symptoms are not very specific in plants, although �dieback� is common, showing up first in the young growth
  • Copper deficiencies commonly occur in highly leached acid sands (such as coastal sandy and sandy loam soils), in loams from sandstone, in peat soils, and in highly calcareous alkaline soils

• Zinc (Zn)
  • Zinc (Zn) is associated with the formation of chlorophyll and of several enzyme systems required for protein synthesis. It also has a regulatory role in the intake and efficient use of water by plants
  • Zinc deficiency symptoms include:
    • Small bronze spots on older leaves of clovers; as spots enlarge, leaves develop a mottled appearance
    • Branching of small, dark green, distorted leaves in the centre of clover plants
  • Typically, zinc deficiency is associated with leached acidic sandy soils, alkaline soils with considerable calcium carbonate content, and soils with high organic matter

• Manganese (Mn)
  • Manganese (Mn) has several plant-growth functions. It is closely associated with iron, copper and zinc as a catalyst in plant-growth processes; is essential for rapid germination; and plays a role in enzyme systems in seed and new tissues
  • Manganese deficiency symptoms include:
    • Yellowing between the veins of young leaves
    • Eventually spots of dead tissue may drop out, leaving a �ragged� leaf
    • Stunting of growth
    • Reduced flower formation

• Iron (Fe)
  • Associated with the production of chlorophyll and helps to carry oxygen around the plant cells. Iron is also involved in reactions that convert nitrates to ammonia in the plant
  • Iron deficiency symptoms include:
    • Chlorosis (yellowing) between the leaf veins of the youngest leaves
    • Tips and margins of leaves remain green for the longest time
    • Affected leaves curve upwards
    • Stunting and abnormal growth
    • Iron is very immobile in the plant. Thus, deficiency symptoms affect the youngest leaves first

• Boron (B)
  • Mainly involved in the movement of sugars throughout the plant and in seed production in legumes. It is also an important nutrient in the metabolism of nitrogen, carbohydrates, and hormones and is involved in the uptake and efficient use of calcium in the plant
  • Boron may induce both toxicities and deficiencies in Australia
  • Boron Deficiency symptoms include:
    • Distorted and chlorotic leaves with darker pigmentation along the leaf margins
    • Red and yellow discolouration, particularly in sub clover
    • Poor growth
    • Low seedset
    • Deficiencies often tend to disappear after rainfall since plant roots may be unable to access soil boron in dry soils. Lucerne is the main crop in which boron deficiency has been identified in Victoria

• Chlorine (C)
  • Thought to stimulate carbohydrate metabolism, some plant enzymes, chlorophyll production, and the water-holding capacity of plant tissues. Chlorine seems to be more important for animals than for plants

• Selenium (Se)
  • Although not essential for plants, selenium is required by sheep and cattle for growth, and for prevention of selenium-responsive myopathy (white muscle disease)
  • Blood tests are the best way of determining if stock will benefit from additional supplies of Se

• For most soils in south west Victoria, there is no clear data on responses to pastures to the application of the trace elements zinc, copper, cobalt, boron or manganese. There are however, special cases such as lighter soils where experience has shown that some trace elements are necessary
• It usually takes a combination of local knowledge, tissue testing and strip tests to resolve exactly what elements are required
• As well as nutrients and organic matter, animal manures contain a wide range of trace minerals that may be useful in correcting pasture deficiencies

• Molybdenum (Mo)
  • Molybdenum deficiencies are more likely in acid soils, and the application of lime may increase its availability. However, peat soils, which are usually acidic, should not require additional molybdenum, as these soils usually have high levels of molybdenum held within the organic matter
  • Molybdenum toxicity is not thought to be significant in plants, but excessive molybdenum levels in plants or high rates of molybdenum applications in fertilisers can sometimes induce copper deficiency in livestock. Therefore, it is generally recommended that copper be included in the fertiliser whenever you apply molybdenum
  • Responses in south west Victoria were first seen in the 1940�s. Substantially better pasture growth followed an application of molybdenum on most basalt plains and coastal plains soils, any soil with a high buckshot gravel content and very light sandy soils
  • Normally applied as an additive to another fertiliser such as superphosphate to ensure even distribution over a paddock

• Can also be sprayed onto a pasture
• Liming makes Mo held in the soil more available, but application of Mo is generally much cheaper than liming unless the soil pH also needs correction
• Typical application rates are 0.05 kg Mo/ha every 5-7 years

• Copper (Cu)
  • Rates of 1.5 to 2 kg Cu/ha applied as fertiliser every 3 to 6 years are required for deficient soils

• Zinc (Zn)
  • Deficiencies may be temporarily induced by cold, wet weather and have been noted to disappear with the onset of warmer weather. Deficiencies are uncommon in pastures in southern Victoria except on the alkaline coastal soils

• Manganese (Mn)
  • There is no evidence in Victoria of manganese deficiency affecting pasture growth. However, manganese deficiency in pastures can be treated by applying manganese sulphate

• Iron (Fe)
  • Deficiencies usually occur on high-pH calcareous soils or in soils that have been heavily limed

• Boron (B)
  • Occasionally, liming may heighten a boron deficiency. Boron deficiency can be induced in turnip fodder crops by lime application, usually at 3.5 t/ha or higher during seedbed preparation
  • If plant tissue analysis indicates a deficiency, then apply born with a fertiliser application and retest in 2 to 3 years. Seek expert advice to determine the appropriate boron types and application rates

• Selenium (Se)
  • Where Se deficiencies in animals is diagnosed, the application of Se onto the pasture may be the most economic ways of getting it into the animal

• What are the optimum nutrient targets for pastures?
• How do I improve soil without using too much fertiliser?
• What are the merits of tissue testing instead of soil testing?

• Trace Elements for Dryland Pastures - Department of Environment and Primary Industries, Victoria


• Trace Elements for Pastures and Animals in Victoria - Victorian Resources Online - Department of Environment Primary Industries, Victoria


• What Nutrients do Plants Require? - (See 6.4 Minor nutrients or trace elements ) - Department of Environment Primary Industries, Victoria

• Fertilisers for pastures - (See page 22) � Department of Primary Industries, NSW


• Soil Fertility - Soil Health Knowledge Bank � Department of Agriculture, Fisheries and Forestry


• Fertilising Pastures :(Chapter 5)- Greener Pastures for south west Victoria (2006) � Department of Environment Primary Industries, Victoria

• Trace Elements for Dryland Pastures. Department of Primary Industries, Victoria.
• Soil Fertility. Soil Health Knowledge Bank � Department of Agriculture, Fisheries and Forestry.
• Fertilising Pastures � (Chapter 5).Greener Pastures for south west Victoria (2006) � Department of Primary Industries, Victoria.

• What Nutrients do Plants Require? (See 6.4 Minor nutrients or trace elements ) - Department of Primary Industries, Victoria.
• Fertilisers for pastures. Department of Primary Industries, NSW.

Page Updated: September 2013
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