Cold wet weather halts growth

Farmer Andrew Sloane from Tullysaran in a field of Cassia winter barley

Farmer Andrew Sloane from Tullysaran in a field of Cassia winter barley

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The prolonged period of cold wet weather over recent weeks had restricted growth of all spring crops sown in late March. Whilst all germinated well, growth of most crops had been particularly slow.

Most crops appear to have recovered from the transient yellowing associated with plants struggling to take up nutrients in waterlogged soils this past week.

The problem was very much the lack of heat, restricting nutrient availability and therefore growth and development. The slight rise in temperature this week has encouraged both weeds and crops to move steadily. To date aphids have been discouraged from flying due to cool conditions and aphicides at present may not be required. It is important to remember the work of the beneficial insects on crops.

The well below average air temperatures up until now mean soil temperatures have also been well below average for the time of year. The Nitrogen mineralisation process in the soil where fertiliser nitrogen is converted to a form that can be taken up by the crop is a soil microbe process and therefore dependant on soil temperature. Hence colder soil has slowed the availability of nitrogen to the crop, and many other nutrients also, particularly manganese.

The application of a broad-spectrum trace-element mix along with key macronutrients at this time is a very useful and beneficial way to supplement the plant’s nutrient requirements during periods of restricted availability, especially when coinciding with phases of rapid growth ie. during tillering and as stem extension begins.

An application of a balanced and readily available source of macro & micronutrients that is not dependant on soil availability at this key time will minimise the adverse effects of restricted soil nutrient uptake.

For winter wheat the T2 should ideally be applied between mid-flag leaf to mid-booting, GS38-45 along with the growth regulator. Most winter barley crops are looking exceptionally clean and should have good yield potential if the weather works in our favour. I think we are well overdue a spell of decent weather, although predicted prices would not excite any of us!

Potatoes

The protracted planting this spring has meant most potato crops have yet to receive weed control. This task must take priority as to delay until after crop emergence will set the crop back even further in an already late season.

Conditions have been ideal for the use of residual products (Afalon, Linurex, Sencorex). Where broad–leaved weed control has yet to be completed and the crop has passed the latest timing for Sencorex. A reduced rate of Sencorex tank-mixed with Titus will provide a wider weed spectrum of weed control than Titus used alone and can be used on emerged crops up to 25cm high where the label allows.

Scutch, other grasses or volunteer cereals are not controlled by the Titus/Sencorex mix. Where these weeds become a problem in coming weeks the graminicide Shogun can be applied. Shogun can cause transient yellowing and is therefore not approved for use on seed crops.

As canopies close, the soil surface will tend to remain damper, encouraging slugs. Timing is critical for effective control, just before the crop meets across the rows. Take advantage of any rainfall by applying pellets just afterwards, as this rain will encourage slugs up onto the soil surface. Potato varieties particularly susceptible to slug damage include Maris Piper, Desiree and Kerrs Pinks.

Blight fungicides move through the plant in three different ways contact, translaminar and systemic. Dithane, Ranman Top, Shirlan and Tizca are all contact fungicides. These products protect only the outer surface of the leaf onto which they are deposited.

Translaminar products such as Curzate M, Invader, Resplend and Revus move into the leaf and redistribute throughout the leaf tissue as it increases in size whilst systemic products such as Consento and infinito move in through the leaf surface and upwards into the new growth protecting this from infection also.

Products that have zoospore activity are the most effective 1st spray, applied at the rosette stage prior to rapid haulm growth. Shirlan or Tizca will control any zoospores that may be in the soil and provide good protection of the new plant.

During the main canopy development phase with the considerable amount of new growth it is essential the product being used is fully systemic to properly protect the new leaves being put on between applications. Later planted crops are higher risk as they produce more new growth between applications than earlier drilled crops, at a time when the level of inoculum in the air is progressively increasing.

If spraying during periods of unsettled weather, rainfastness of all products will be further improved with the addition of a sticker to the spray solution. Guard is a latex sticker and will improve the retention of the fungicide onto leaf surface, so improving both adhesions onto the leaf immediately post application and over the following days should rainfall levels remain high.

The way the blight product is applied is as important as the product choice. Make sure nozzle type used is correct to ensure sprayer pressure; droplet size and water applied is as directed on the label. Inspect and calibrate nozzles regularly to maintain performance. Never use any blight product at reduced rates. Do not spray when the leaves are wet as this will significantly increase the likelihood of runoff.