Some nutrients are required in large quantities by plants (Major or Macro nutrients) and some in very small quantities (Micro or Trace elements). None the less they are a vital ingredient in growing healthy plants and in turn healthy livestock, high yields and profitable returns.
Copper is necessary for chlorophyll formation in plants and assists with several other plant reactions. Plants supplied with good levels of copper have stronger cell walls and are more resistant to fungal attack. Copper deficiency in WA soils is extremely common. Most soils have received a copper application as new land, and many soils have had more than two applications. Organic soils are commonly copper-deficient. These soils often contain large deposits of copper that is unavailable to plants. In WA, copper deficiency is most common in sandy soils , low in organic matter content. Copper is required in very small amounts in the plant. Concentrations of 2 ppm are adequate in most cases in youngest leaves, compared to nitrogen at 25000ppm. Copper deficiency can be corrected by soil or foliar application. Copper sulphate is the most common form of copper fertilizer, but copper chelate and copper oxide are also used.
Copper is important for lignin production, which is also responsible for stem strength and rigidity. Therefore the first symptoms seen may be a wilted look, regardless of soil moisture status. Copper has variable mobility in the plant. It may move from the oldest leaves as nitrogen moves, but in nitrogen adequate situations, where the plant will continue to draw nitrogen from the soil, copper will not move. The earliest symptoms appear on the youngest growth.
No leaf symptoms Straw weak below head – prone to wind loss Darkening of nodes Some shrivelled grain Yield loss may be 20%
Most ears contain shrivelled grain – some are empty Occasional tiller abortion Often straw purplish grey on the sunny side Darkened nodes and glumes (around seed) Plants remain green after others mature Usually no leaf symptoms Yield loss 20 – 60% Moderate deficiency Few normal ears Grain is shrivelled, white heads Rat tailed or tipped heads Aborted tillers Plants stay green Leaf tipping (withertip) on youngest leaves Yield loss 50 – 90%
Nearly all tillers aborted Nearly all ears die prematurely Ears may not emerge boot Continue to tiller – grass clump Youngest leaves white Yield loss 90 – 100%
In crops, copper can be applied to the soil at a rate of 2kg/ha of copper. This application would be expected to last for 5 years in a full cultivation system. In a No-Till system, growers will need to look towards more frequent applications of copper, as there is insufficient soil disturbance for copper uptake.
Copper deficiencies may also be corrected with sprays in sulphate and oxide formulations. The choice of spray will depend the magnitude of the deficiency and mixing compatibilities with broadacre herbicides.
Zinc is involved in the synthesis of plant growth substances, enzyme systems and is essential for promoting certain metabolic reactions. It is necessary for the production of chlorophyll and carbohydrates. Zinc is immobile within the plant, so symptoms first appear on the younger leaves.
Zinc deficiency in WA is common, although on the predominately lights soils, it is not the recurring problem that copper deficiency is. Zinc become less available under high pH conditions. Soils most likely to show deficiency symptoms are the heavy, highly alkaline soils of the south-east.
Zinc is required in very small amounts in the plant, but it is used 5 – 10 times more than copper. Concentrations of 15ppm are adequate in most cases in the youngest leaves.
Usually seen in young plants, early in the growing season. More severe when soils are cooler and wetter
Deficiencies usually show on the middle leaves and extend to the new growth
Mild deficiency – pale green stripe down either side of the main vain of fully emerged leaf. Leaf tissue dies in the stripe and turns pale brown (tram lines)
Necrotic patches appear
Severe – general paleness of leaves Stunted plants, Diesel soaked appearance, Necrotic areas about halfway along the leaves - causing them to bend in the middle. Necrotic areas increase and are surrounded by yellow mottling areas. Middle leaves collapse in the centre.
Yield losses can be only slight with plants showing some symptoms. Seedlings and plants affected by mild zinc deficiency early in the season and under cool wet conditions may recover as the season warms and day length increases.
Soil applied zinc rates can be as high as 5kg/ha, although 200 – 500g are more common. Zinc, like copper is immobile in the soil, therefore a full cultivation is important for plant uptake. In No-till systems, higher zinc rates may be required for essential early plant growth.
Zinc foliar sprays and seed dressings are also common. These are often used in conjunction with zinc fertilizers in highly alkaline soils where the zinc requirement is increased. Foliar sprays and seed dressings are solutions for the year of use only.
Availability – Sulfates or oxides?
Zinc is mainly applied as zinc sulfate or zinc oxide. Chelates are also used, but mainly in liquid form. Sulphates are regarded as being more soluble (and more available) than oxide formulations. However, in the soil environment both formulations react with soil constituents and become immobile in the months after application. Agronomically, a product which incorporates sulfates, oxides and oxy-sulfate forms is considered best management for zinc applications. More important than the form of nutrient used, is the distribution through the soil. The more sites available for the plant roots to intercept the less chance of deficiencies occurring.
Manganese functions primarily as a part of enzyme systems in plants. It activates several important metabolic reactions and plays a direct role in photosynthesis by aiding chlorophyll synthesis. Manganese promotes germination and accelerates maturity of the plant, while increasing the availability of phosphorous and calcium.
Manganese deficiency is widely distributed throughout the south west of WA. It is usually confined to irregular but clearly defined patches of a few m2 up to 20 ha. With severe deficiencies grain loss may be 100%. The main regions of deficiency are;
South western edge of the wheatbelt from the gravely white gum soils (south Moora/New Norcia) wandoo and mallet soils (West Brookton, Narrogin, Wandering, Wickepin, Katanning) and into fluffy red morrel and blue mallet soils around Dumbleyung, Kukerin, Kulin and Corrigin.
Narrow coastal strip of lime sands from Northampton to Israelite Bay.
South Jerramungup/Esperance sands. Other areas, usually associated with gravel soils.
Most of these soils are associated with gravel and have large reserves of Manganese in them. However it is tightly bound as insoluble compounds. Applications of manganese fertilizer is often unsuccessful as the applied manganese is bound to the soil very quickly.
Symptoms are generally seen from early tillering. They occur as yellow-green patches with irregular, but defined edges. These become paler and the plants wilt and droop in warm weather. All the leaves of wheat, barley and oats become pale, but symptoms show first on older leaves before moving to newer growth. Pale leaves will become limp and soft, eventually dying, producing a dead and wilted flag leaf.
Manganese deficiency can be corrected by;
- Mixing 15kg/ha manganese granule with fertilizer
- Foliar application of 4kg/ha Manganese sulphate