Field Research & Agronomy

Trace elements are only required in small quantities, acting as essential nutrients for plant growth. They’re a vital ingredient for producing healthy livestock, high yields and profitable returns.

Copper (Cu)

Copper is only required in small amounts in plants, but it is necessary for multiple functions, including chlorophyll formation and plant reactions. Plants supplied with good levels of copper also have stronger cell walls and are more resistant to fungal attack.  

Copper deficiency can be corrected by soil or foliar application, with copper sulphate being the most common form of copper fertilizer. Concentrations of 2ppm are adequate in most cases in youngest leaves, compared to nitrogen at 25000ppm.

Copper deficiency symptoms

Copper is important for lignin production, which is also responsible for stem strength and rigidity. As a result, a wilted appearance will be one of the first symptoms, regardless of soil moisture status. As the deficiency progresses, here’s what to except.

Slight: No leaf symptoms, straw weak below head, prone to wind loss, darkening of nodes, shrivelled grain, and a 20% yield loss.

Mild: No or few leaf symptoms, empty ears or ears containing shrivelled grain, occasional tiller abortion, purple/grey coloured straw, darkened nodes and glumes (around seed), plants remaining green after others mature, and a 20 – 60% yield loss.

Moderate: Few normal ears, shrivelled grain, white heads that are rat tailed or tipped, aborted tillers, plants that remain green, leaf tipping on youngest leaves and a 50 – 90% yield loss.

Severe: Nearly all tillers aborted, ears prematurely dying or not emerging, boot Continue to tiller , grass clumping, youngest leaves turning white, and a 90 – 100% yield loss.

Correcting copper deficiency

In crops, copper can be applied to the soil at a rate of 2kg/ha of copper.

Full cultivation system: Application would be expected to last for 5 years.

No-till system: More frequent applications of copper may be required.

Copper deficiencies may also be corrected with sprays in sulphate and oxide formulations. The choice of spray will depend the scale of the deficiency and the mixing of compatibilities with broadacre herbicides.

Zinc (Zn)

Zinc is essential for promoting certain metabolic reactions and is involved in the synthesis of plant growth substances and enzyme systems. It’s also necessary for the production of chlorophyll and carbohydrates. Deficiency in WA is common, becoming less available under high pH conditions. However, it is not the recurring problem that copper deficiency is.

Zinc is only required in plants in very small amounts, but it is used five to ten times more than copper. Concentrations of 15ppm are adequate in most cases in the youngest leaves.

Zinc deficiency symptoms

Zinc is immobile within the plant, so symptoms first appear on the younger leaves, early in the growing season. Deficiencies usually show on the middle leaves and extend to the new growth.

Mild: Seedlings and plants affected by mild zinc deficiency early in the season and under cool wet conditions may recover as the season warms. Symptoms include:

• Pale green stripe down either side of the main vein of the fully emerged leaf.
• Leaf tissue dying in the stripe and turning pale brown (tram lines).
• Necrotic patches.
  

Severe: When there is a severe zinc deficiency, the following symptoms may be present: general paleness of leaves, stunted plants, diesel-soaked appearance, necrotic areas about halfway along the leaves surrounded by yellow mottling areas, and middle leaves collapsed in the centre.

Note: Deficiency is likely to be more severe when soils are cooler and wetter.

Correcting zinc deficiency

Soil applied zinc rates can be as high as 5kg/ha, although 200 – 500g are more common. Zinc is immobile in 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 and are used in conjunction with zinc fertilizers in highly alkaline soils. Foliar sprays and seed dressings are to be used as solutions for the year of use only.

Manganese (Mn)

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 also promotes germination and accelerates maturity of the plant, while increasing the availability of phosphorous and calcium. With severe deficiencies, grain loss may be as high as 100%.

Manganese deficiency is widely distributed throughout the south west of WA, mainly in soils associated with gravel soils. Most of these soils 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 binds to the soil very quickly. Fertilizers that acidify the root zone (MAPSZC®, Vigour®, MAXam) will release this manganese for long enough to grow the crop. To be effective, the fertilizer has to be drilled next to the seed.

Manganese deficiency symptoms

Symptoms are generally seen from early tillering and can include:

• Leaves developing yellow-green patches with irregular, defined edges that become paler over time.
• Pale leaves that become limp and soft, eventually dying, producing a dead and wilted flag leaf.
• Plants that wilt and droop in warm weather.

Correcting manganese deficiency

Manganese deficiency can be corrected by the following two methods:

1. Mixing 15kg/ha manganese granule with fertilizer
2. Foliar application of 4kg/ha Manganese sulphate