The catchy weather in April and early May has meant Septoria pressure has been extremely high especially on those earlier drilled winter wheat crops. The ear has now emerged on many crops of Extase and mildew is present on the more forward lush crops of Graham. Aphid numbers are currently very high in both winter and spring cereals. Any late drilled spring barley should be inspected and if colonies are found on over 50% of plants it should be treated to reduce the risk of BYDV.
Most spring cereal crops continue to benefit from the recent improved temperatures with many now racing through the growth stages.
As soils warm up and daylight hours are considerably longer the likelihood of crop stress through too little moisture, or not enough nutrient availability to support the potential rate of growth is now showing up in later drilled crops. As a result, many fields are beginning to show variation of colour and growth, and such variation is very difficult to address in a satisfactory way. Manganese (Mn) deficiency is widespread in much of our local soil types, and particularly damaging if not treated. Continuous cereal cropping, ground recently limed and dry soils all increase the likelihood of deficiency. Symptoms begin with small pale green speckles appearing throughout the leaf and these will progress to turn brown unless treated. Barley is particularly susceptible to manganese deficiency.
A young plant that is growing extremely rapidly is producing a huge amount of new plant tissue each day. This rapid growth is limited only by the availability of nutrients to synthesise biomass, dependant on soil fertility and the plant’s own root development to take up the nutrients. It is at this time therefore when nutrient deficiencies are most likely to appear and in doing so, suppress growth rates.
The application of a broad-spectrum trace-element mix along with key macronutrients during this time is a very useful and beneficial way to supplement the plant’s nutrient requirements during periods when availability does not meet demand, most likely to coincide with phases of rapid growth. Application of a balanced and readily available source of macro & micronutrients that is topping up what is being made available from the soil at this key time will minimise the adverse effects of restricting nutrient availability.
CEREAL HIGH N supplies 250gm N, 38gm Mg, 45gm Cu and 15gm Zn per hectare.
The T1 application should be applied from late tillering to the start of stem extension, GS24-31. Since this treatment is primarily for insurance and the risk of infection being present at this time is low, it follows that rates can be reduced compared to the winter crop. The T2 is the more responsive timing in spring barley when Ramularia is also a significant risk, therefore more of the spend should be directed at the T2 timing. This application should be applied from first awns visible to ear completely emerged, GS49-59. Also bear in mind too that preventing Rhyncho infection is much more effective than trying to control it curatively. Once infection has come in, any eradicant treatment has limited efficacy, and the infection will stress the crop, increasing the risk of Ramularia infection sooner rather than later.
Application of SELON at early tillering will have increased tiller and ear numbers and therefore yield potential, but will not have given any reliable strengthening of the straw. Stems that extend rapidly during the stem elongation phase are more likely to be weaker and so there is a greater risk of lodging especially where the crop is being pushed on with nitrogen. SONIS/CRATUS can be used but its cut-off in spring barley is 2nd node, GS32. CANOPY is a very useful alternative, safe to the crop and able to be used right up to and including full flag leaf, GS39.
Because the application of SELON at mid to end of tillering (GS23-30) does give reliable later season lodging control in wheat, it is less likely than spring barley that spring wheat will need a growth regulator towards flag leaf unless the crop is particularly dense.