Winter cereal crops – wheat, barley, oats and rye - planted out during September have emerged strongly and continue to grow on well.

But according to Teagasc tillage specialist, Shay Phelan, growers will have a ‘date with destiny’ where these crops are concerned at the end of this month (October).

He explained: “These crops were drilled at a time of high air and soil temperatures.

"Aphid populations have been extremely high over recent weeks.

Meanwhile, Teagasc is highlighting the various potash fertiliser strategies that can be applied to winter cereal crops, according to soil type.

Potassium

Potassium (K) may receive less attention than nitrogen, though cereal crops have a substantial requirement for it.

However, the application of the crop nutrient requires a little more thought in autumn.

In essence, potash plays an important role in water regulation, crop strength and stress tolerance, while good K nutrition can also reduce lodging and brackling.

Traditionally, large dressings of the nutrient are often applied to tillage soils in autumn. But should all of this requirement necessarily go out then?

According to Teagasc, the starting point is the soil test. The target for mineral tillage soils is Potassium Index 3, which indicates an adequate soil supply for crop growth.

Applications are then based on soil status, expected yield, and crop offtake.

Straw management is also important.

A 10t/ha winter wheat crop removes around 98kg of potassium per hectare, where straw is removed, compared with 47 kg K/ha where straw is chopped and incorporated.

The role of soil type

Soil type also plays a key role, as soils differ considerably in how they hold and release K.

Heavier soils generally have a greater capacity to retain potassium. Light, sandy soils, however, have less capacity to hold the element.

This increases the risk of movement below the main rooting zone where applications are greater than the crop’s immediate requirement.

Large reserve applications are therefore generally discouraged on these soils.

Some soils can also fix potassium within clay minerals, making it less readily available to crops.

Previous soil tests can provide useful clues here. If the potassium index remains stubbornly low over successive soil tests, despite adequate nutrient applications, potassium fixation may be part of the explanation.

In other words, if plenty of potassium has gone in but the soil test refuses to budge, it is worth asking where it has gone.

Timing therefore matters. On sandy or organic soils, current advice is not to build large soil K reserves, but to apply sufficient K annually to meet crop requirements.