East: Soil temperatures slowing release of organic N

With soil temperatures at 10cm around 4.2C, things are just starting to wake up after ticking over for the last few months. Although it’s very clear that things are not as warm as we may wish them to be – you only have to look at the purple oilseed rape crops, the blue/bronzed winter wheat and the winter barley which is as “gold as a Guinea” to realise that cold soil temperatures are not allowing soils to mineralise and release their organic stores of nitrogen – if they were doing this, things would not look as horrible as they do – even the daffodils have stopped growing!

This is the man upstairs’ way of telling farmers not to rush out top dressing cereal crops, because with little or no growth, any rainfall events are simply going to leach the ammonium nitrate through the soil before the inactive cereal crop has a chance to grab hold of it – ergo . . . it’s too early to go – but as with most years it’s a fact that many farmers choose to forget.

Disease levels remain much as they did before Christmas, with many fields exhibiting high levels of Septoria tritici and yellow rust within the base of the canopy – just a reminder that whichever course you choose to steer at T0, the protectant qualities of chlorothalonil should form a big part of your mix.

Atlantis (iodosulfuron + mesosulfuron) applications have yet to begin thanks to wet leaves and poor travelling conditions, but will start once soil temperatures have been at or above 4C for five days. Getting in at the earliest opportunity is the key to getting the most out of Atlantis in any season – but hitting a dry leaf and making sure it stays dry for at least two hours after application remain critical.

Wheat bulb fly symptoms have yet to appear, but rabbits, hares, dear, and suspected wildebeest are notable in their numbers.

The mildew that was so widespread in winter barley before Christmas has all been controlled by the frosty nights without a splash of mildewicide being applied. It has also been far too cold to consider the use of Axial (pinoxaden) as a last resort on any blackgrass, which has survived the residual onslaught in winter barley,  you just have to keep your fingers crossed that it will do some good when you do get to it and, to be fair, keeping your fingers crossed is probably more likely to work on resistant blackgrass than the Axial.

Oilseed rape, however, is succumbing to the attentions of pigeons, with high levels of damage seen, but it is beginning to wake up after the winter and first applications of nitrogen plus sulphur are going on as I write this. Clearly the same is true for OSR, as it is for cereals in terms of soil temperatures. However, the root system is far deeper and more advanced in OSR and, with many growers using urea plus sulphur mixtures, this is far less likely to leach through the profile if wet conditions arrive. Being driven by the fact that it takes between four and five weeks for the SO3 to get into the plant through the roots and, as SO3 has to be available at stem extension, a week of rising temperatures will see OSR begin to move very quickly.

Disease levels, particularly light leaf spot, are increasing now and, over the next seven to 10 days it’s likely we will have to go out and put a protectant fungicide on to stop this problem getting any worse – we have nothing but protectants in the fight against LLS, so timing is critical. About 15% of plants affected or one plant in seven affected by LLS is the threshold and, as I write this, I’m finding nothing worse than 1% or one plant in 100 so we still have time.

Staying with OSR, the restrictions on new label Galera (clopyralid + picloram) should not be ignored. It is now a legal requirement that no crop other than cereals is planted for 36 months after the use of the herbicide product. This is not a crop safety issue, it’s to assess the impact of residues of picloram on non-cereal crops such as pulses – if you ignore the label and you get an RPA inspection you wish you hadn’t! So if you have cleavers and if anything other than a cereal crop is likely to be drilled in the next three years, you may be better to put up with them and apply straight clopyralid for the thistles, groundsel, mayweed etc, rather than fall foul of the RPA inspectors.

Although some spring barley is being drilled now on the lighter land, it’s still too wet to put spring beans in the ground on my farms, indeed it’s too wet to travel on many fields at all in Lincolnshire at present. This is quite surprising in some ways considering I only registered 28 mm of rain in January and just 25 mm of rain throughout February – the legacy of 2012 with slumped soils and silted up field drains won’t be going away in the near future!

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