South: Pre-emergence herbicides work well in spring cereals

Always the eternal optimist, one advantage of this year’s challenging spring has been to provide more than adequate amounts of moisture to allow pre-emergence herbicides to work well on the last of the spring cereals being drilled now. The majority of which were finally drilled last week into mainly good conditions.

We have come to the end of a difficult week weather wise with some cold nights and the odd white frost. Moderate daytime temperatures been hovering around 4-5C at times. Crop growth is very uneven in places and still somewhat slow. With some wheat crops looking a bit starey. Slugs are very active on spring cereals and grazing is still taking place on even strong crops of winter wheat.

Despite the weather, forward wheat crops have or are now receiving a T1 fungicide based around the SDHI isopyrazam and epoxiconazole plus chlorothalonil. On barley, T1s have consisted of prothioconazole and trifloxystrobin. The cool unsettled conditions have maintained the disease risk, with yellow rust showing up in crops where T0s were delayed. The septoria risk has increased too, although symptoms could well be slower to show, as the latent period will be extended in the cooler temperatures.

Oilseed rape is slowly coming into full flower, but as usual many crops are very variable. With crops now flowering, subsequent weather conditions will heavily influence the risk of sclerotinia. To date the latest AHDB report indicates that the risk of infection remains relatively low in the east, with more spore release being detected in other areas of the country. When planning a flowering fungicide strategy the pressure from aphids and seed weevils will need to be factored if they reach threshold levels. For seed weevil this is 0.5-1 weevil per plant.

Tissue testing of winter wheat so far this year is high lighting low levels of magnesium, zinc and boron in many samples. We are well used to dealing with N, P, K, sulphur and manganese, but it seems we are still not adequately addressing the other important trace elements. In house trials are showing positive benefits of applying additional trace elements, even when the soil results may be showing little or no deficiency. Improvements in terms of overall yield through improved green leaf retention, more ears per sq m and grains per ear and generally improvements to overall plant health have been observed. It may also lead to plants having better tolerance to disease? Something echoed at a recent farm walk in Kent, hosted by Biodiversity, Agriculture, Soil and Environment (BASE) member Andrew Howard.

Andrew is currently doing a Nuffield Scholarship looking at companion cropping and he has planted a range of companion crops this spring on the home farm. The range of crops being trailed together include; buckwheat and linseed, lucerne, buckwheat and linseed, to mention just two. All under a no-till system, while the technique of under sowing winter wheat is also being evaluated in crops drilled last autumn. Andrew has also for many years been looking at fine tuning plant nutrition, soil biology and the overall benefits of improving soil health. It will be very exciting to see how these crops perform this season.

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