News

Welcome to the first crop crack of 2024 and for the first time in many months we look set to get at least a few settled days. Growth is not what we would expect for the middle of April, and it is important to note that stress in whichever form will affect nitrogen utilisation. Nevertheless, top dressings are kicking in and crops are starting to come away. The poor economics across the agri-sector coupled with the persistent bad weather conditions have left a very depressive mood amongst many of the farmers I have been speaking to in recent weeks.

Winter Barley GS30 – GS31

All crops have completed tillering, with the most forward fields past 1^st node, GS31. Most are looking well considering the wet conditions over the winter. There are good plant counts and tiller numbers, but the mild winter means disease is already well established on these young plants with Rhyncho, mildew and net blotch showing in all.  Rhyncho remains the most damaging disease of barley, seriously damaging yield potential if not controlled quickly and effectively.

Winter Wheat GS22 – GS31

Growth stages vary widely depending on drilling date, but most are at various stages of tillering. Most have reasonably good plant numbers but some fields have suffered from waterlogging and unfortunately stitching in, up until now has been impossible. Septoria is established in all crops but particularly so in earlier drilled fields.

Disease Control

Rhynchosporium and Septoria are the two most damaging cereal diseases in NI. Both have always been more effectively controlled preventatively, but in previous times the curative properties of the azole family were able to rescue a bad situation, particularly in wheat, this is no longer the case.

Timing of fungicide applications and rates used are every bit as critical as product choice to achieve the maximum potential response. To ensure the main disease programme persists right through to ripening, it is advisable that all crops should by now have received a T0 fungicide where conditions have allowed. Farmers should be aiming to apply their main T1 fungicide application within the next week or so. Due to ground conditions to date, very few T0 sprays have actually been applied. Depending on crop stage, there may still be a good case for a T0 treatment. A T0 sets up a cleaner crop for its T1 treatment, which in turn can then can be less dependent on curative performance and more on preventative. Teagasc trials last year looking at the benefit of a late applied T0 were striking. They compared a very strong T1 + T2 programme with and without a T0.  The T0 application of full rate THIOPRON + half rate COMET (applied on 14^th April 2023 at GS31, just 11days before the main T1 went on), gave a significantly cleaner crop at flag leaf, which went on to translate through to more than a 0.5t/ha yield improvement in wheat.

T2 and T3 applications following at 4-5week intervals, ie mid-May and mid-June. This T1 timing should coincide with the beginning of stem extension between 1^st and 2^nd node, GS31-32.

Holding the T1 timing to GS31-32 should ensure T2 in barley and T2 & T3 in wheat be optimally timed to avoid extended gaps, maintaining persistency right up to and during senescence. Where a crop has not received a T0 treatment product rate at T1 will need to be increased to take account of this.

Weed control

Many crops did not receive an autumn herbicide and for those still to be treated, control of Annual Meadow Grass (AMG) is the most pressing issue. HAMLET is an excellent option for AMG in wheat only, there is no similar late option for barley. Note that HAMLET will only control AMG that has already emerged; unlike the autumn products it has no pre-emergent activity. Where the AMG has been controlled in the autumn but for example chickweed, cleavers or groundsel are likely to be a problem, ZYPAR is an excellent stand-alone broad-spectrum herbicide controlling these and most other emerged BLW. It also works best when the weeds are growing actively and has post-em activity only, therefore delay use until all cleavers have germinated and temperatures have risen to encourage growth. ZYPAR is also an excellent tank-mix partner with HAMLET

Growth regulation

When applied before 1^st node, GS31, application of certain chlormequat growth regulators can significantly increase tiller numbers. Chlormequat works by suppressing apical dominance, ie main stem development. In doing so it diverts the plant’s resources into producing and supporting more tillers. Particularly in wheat but in barley also, more tillers will go a long way towards compensating for low plant counts, ultimately increasing yield.

Correct timing is critical to maximise this effect. The earlier it is applied during tillering the greater the tiller effect, but note early application to increase tiller numbers will also reduce its effect on lodging. Application of a chlormequat based growth regulator often goes on with a T1 fungicide application sometime around 1^st-2^nd node, GS31-32. At this timing it is too late to affect tiller numbers and survival but will maximise the stem stiffening effect.

Early application will also increase root growth and so reduce stem-base lodging. Stem-base lodging is where the plant folds over at the soil surface as a result of poor anchorage in the soil, and is caused by poor root ball development, more likely when the seedling develops in wet soils that limit root development. All winter crops have rooted very shallow this season as a result of the persistently wet conditions and therefore stem-base lodging is likely to be a significant problem later this season.

Nutrient Deficiency

A combination of waterlogged soils, plants already suffering from restricted nutrient uptake and plants now trying to grow, is showing up Mn deficiency in many barley crops. Continuous cereal ground and ground recently limed is most prone to deficiency. Symptoms begin with small pale green speckles appearing throughout the leaf and these will progress to turn brown unless treated.

Copper deficiency often accompanies Mn deficiency – its symptoms are complete browning of the leaf tip especially the youngest leaves, and apparent wilting of the plant. Treatment will be most effective if treated immediately symptoms are recognised.

With air quality significantly improving over the last two decades, the most important source of sulphur to the soil coming from the pollutant gas sulphur dioxide has also reduced significantly. Whilst its deficiency is now being recognised and corrected on grassland through the application of high sulphur compound fertilisers, its impact in cereal crops in NI has by and large been misidentified or overlooked. After nitrogen, phosphate and potash, sulphur is the next most important element required by all crops, used to make essential sulphur containing amino acids and proteins in all plants. Soil sulphur is easily leached especially from light to medium soils, making shallow-rooting plants particularly vulnerable to deficiency. Deficiency causes paling in the cereal plant, caused by a reduction in chlorophyll production and even in the absence of any symptoms, decreased efficiency of nitrogen utilisation. Whilst often mistaken for lack of nitrogen, sulphur is not very mobile within the crop and therefore deficiency is most pronounced on the younger leaves; the opposite to nitrogen deficiency which affects the oldest leaves first. Crops of both wheat and barley with high yield potential are particularly responsive to one to two applications of foliar sulphur at the timings of rapid growth.