A range of crop nutrient deficiencies are now visible in spring cereals, which is a direct result of the ongoing dry weather, according to Teagasc.
Phosphorus (P) deficiency is characterised by purple/red colours on older leaves and poor tillering.
Potassium (K) shows as yellow tipping, starting on the older leaves that moves down the leaf margins. The affected leaf feels like paper and eventually turns white,
Magnesium (Mg) deficiency is recognised by yellow striping down the older leaves between the leaf veins.
Manganese (Mn) deficiency shows up a similar striping to Mg but on newer leaves and spotting between veins.
In addition, Mn deficiency is evident in affected fields by a “wheeling” effect – where tramlines or wheel marks appear greener than the rest of the crop.
As soils continue to dry and with no rain predicted, other deficiencies such as zinc (Zn) and copper (Cu) are inevitable in fields with a history of such issues.
Actions that can be taken
While rain would alleviate a lot of the deficiencies currently being observed in spring cereals, if there is a history of a specific nutrient deficiency problem associated with a site, or a nutrient deficiency presents in the crop and the symptoms persist, action may be required in the form of foliar applications.
Correct identification of the deficiency is important. While soil analysis can help to identify high risk areas for most of the trace elements, for some, such as Mn, tissue analysis can be more accurate.
Research shows that there is no economic justification for the addition of trace elements mixes prophylactically, where no deficiency is evident.
Additionally, due to the small quantities that some trace elements are required by the crop, adding these unnecessarily could have a negative impact on crop performance.
Applying foliar trace element treatments in hot and dry conditions requires some careful considerations.
The following are some tips for the foliar applications of trace elements to crops:
- Apply early in the morning or late in the evening – stomata are open and temperatures are generally cooler at these times, reducing evaporation and preventing leaf scorch.
- Check the weather forecast for suitable spray conditions. Avoid applying immediately before rain and in very high or low humidity. Avoid applying in midday sun.
- Ensure good leaf coverage.
- Choose appropriate formulations – chelated compounds or inorganic formulations, that can be absorbed quickly and efficiently through the leaves. Although more expensive, these may be more effective in drought conditions compared to inorganic salts.
- Apply label rates: too much trace element solution in dry conditions can stress the crop further.
- Do not mix incompatible products: some trace element solutions or pesticides can react negatively with each other, reducing efficacy or even causing damage to the plant.
Growers should always check compatibility before mixing treatments. In a severe deficiency situation, it is advisable to address the deficiency before applying further pesticide products.
