Cereal micronutrients
Maintaining Maximum Yield Potential
Certain elements are important for the healthy growth of cereals. The main nutrients of nitrogen, phosphorous, potassium and sulphur are well known to the grower, with high levels applied routinely after soil residual and rotational consideration have been taken into account.
However, other key elements are essential to sustain healthy plants although these can often be overlooked. These elements will help to maintain important functions throughout the plant's life cycle including:
- Plant vigour
- Winter hardiness
- Disease resistance
- Root development
- Flowering
- Uptake of nitrogen
- Shoot growth
- Grain fill
The main micronutrients in cereal nutrition
For wheat and barley in the UK, the most important micronutrients are manganese, magnesium, copper and zinc (other less important elements for temperature climates are boron, cobalt, iron and molybdenum).
Manganese
Manganese is acknowledged as a stress reliever.
Deficiency Symptoms:
Plants are yellow or pale green and have a floppy growth habit. In wheat, interveinal white streaks occur. In barley, interveinal brown spots can be a symptom of manganese deficiency. Early in the growth cycle, plant stunting often occurs. In extreme cases, plants will die.
Magnesium
Magnesium is fundamental to plants. It is essential for photosynthesis as magnesium is the central building block for chlorophyll. It is active in the movement of phosphates and in the regulation of cellular water resources.
Deficiency Symptoms:
There is a loss of healthy green colour between veins on older leaves, which is usually followed by chlorosis and/or the development of brilliant colours. In severe cases the leaves may turn yellow, red or purple. Sometimes, leaves curl and leaf necrosis may occur. Premature defoliation may follow. Yield and growth may be reduced.
Copper
Copper is a catalyst in enzymes which carry out essential biochemical functions, especially those involved in respiration and those that convert nitrogen to protein. In cereals it is of major importance in grain production and ear development (pollination).
Deficiency Symptoms:
Cereals show whitening of the tips of the young leaves which may twist in spirals and bend over at right angles to the stem. Growth may be severely checked. Ears may be few, underdeveloped and appear white at harvest, may sometimes be trapped within the leaf sheath. On chalk soils, plants can look normal until the plant comes into ear when deficient plants turn dark olive green. Yield is reduced drastically and there may be a profusion of "rat tailed" ears.
Zinc
Zinc is essential for photosynthesis and is important for rooting and maturity. It also assists in starch formulation.
Deficiency Symptoms:
These are most noticeable in the early stages of growth. Yellow streaks are seen at the second leaf stage on wheat and barley. On barley, white streaks appear along the leaf edges, often bleached. Plants can remain small and stunted with a "spikey" appearance. High numbers of late tillers are produced which remain immature. At ear emergence, awns can be twisted and wavy with ears distorted.
Correcting deficiency symptoms
It is false economy to wait until deficiency symptoms are visible before addressing nutrient requirements. By the time symptoms are evident, the crop is likely to have been suffering for a considerable time. Any yield potential will already have been reduced. Providing a balanced supply of essential nutrients from the start, to ensure a healthy plant, is more sensible than taking action after deficiency symptoms occur.
Nutrients needing supplementing can be predicted by:
- Knowing the key nutrients for that crop
- Understanding nutrient availability within soil types
- Recognising conditions which further limit availability
- Being aware of how requirements change over the growing season
| Soil Type | Manganese | Magnesium | Copper | Zinc |
|---|---|---|---|---|
| High pH | x | x | x | x |
| Low pH | x | |||
| High organic matter | x | x | ||
| Chalks | x | x | x | |
| Peats | x | x | ||
| Clay | x | |||
| Sand | x | x | x | |
| Outside Effects | ||||
| Poorly drained | x | x | ||
| Over liming | x | x | x | |
| Compacted soils | x | x | ||
| Recent ploughed grass | x | x | ||
| Cold seedbeds | ||||
| High potassium | x | x | ||
| High calcium | x | x | ||
| High nitrogen | x | x | ||
| High phosphate | x | x | ||
| High potash | x | |||
| High copper | x | |||
| High iron | x | |||
| Low phosphate | x | x | x | |
| Low sulphur | x | |||
| Low nitrogen | x | |||
| After set-aside | x | x | x | x |
Suggested Micronutrient Programmes for Cereals
(In absence of any specific deficiencies).
Winter Wheat
| Autumn | Manganese (+/- copper) - helps rooting, establishment and stress resistance (also zinc if land is known to be deficient or conditions are unfavourable). |
|---|---|
| GS25-31 | Magnesium for chlorophyll production - ready for large demand at GS32 (also zinc if land is known to be deficient or conditions are unfavourable). |
| GS39 | Magnesium onto quality wheats (also zinc if land is known to be deficient or conditions are unfavourable). |
(Manganese can be applied at any time if plants become stressed.)
Winter Barley
| Autumn | Manganese (+/- copper) - helps rooting, establishment and stress resistance (also zinc if land is known to be deficient or conditions are unfavourable). |
|---|---|
| Early Spring | Manganese (+/- copper). |
| GS25-31 | Magnesium for chlorophyll production - ready for large demand at GS32 (also zinc if land is known to be deficient or conditions are unfavourable). |
(Manganese can be applied at any time if the plants become stressed.)
Spring Barley
| GS25-31 | Manganese + magnesium, particularly on lighter land (+/- copper). |
|---|---|
| GS37-39 | Manganese + magnesium. |
(Manganese can be applied at any time if the plants become stressed).
Soil Nutrient Levels
| Manganese (Mn) (ppm) | Magnesium (Mg) (ppm) | Copper (Cu) (ppm) |
Zinc (Zn) (ppm) |
|
|---|---|---|---|---|
| Deficient | <1.5 | <25 | <1.8 | <1.5 |
| Low | 1.5 - 2.5 | 25 - 50 | 1.8 - 3.8 | 1.5 - 2.8 |
| Satisfactory | >2.5 | 51 - 100 | >3.8 | >2.8 |
(ppm = parts per million)
These figures are guidelines only. Full interpretation and treatment recommendations can only be made after considering visual symptoms and field history, as well as interactions between elements.
If history on your farm gives evidence of deficiencies, it is advisable to seek further advice, either from a consultant or advisor who could then design a programme after soil sampling and/or tissue testing.
Syngenta Seeds would like to thank Headland Agrochemicals for their contribution in compiling this information.
Warning
Symptoms of micronutrient deficiency can look similar to virus infection,for example, Barley Yellow Mosaic Virus and Barley Yellow Dwarf Virus. In these circumstances, send plants away for analysis. If virus is confirmed, grow resistant varieties.
