Spud Special: Cold soils cause for concern

Soils are drier than anyone would have imagined a month ago although in some areas, field margins and valleys, snow cover remains. Soil temperatures are still around 3-4C, but as one grower commented this is in an improvement over the 0C when he began planting. Even sheeted crops that went in 3 weeks ago are barely moving, with soils taking a long time to warm – even under fleece.

On the positive side growers won’t have to wonder what would have happened if they had planted more in March. Hopefully the slow start to planting nationally will leave less time for speculators to put more crops in the ground at the end of season on the back of a high price year. This should mean we get some much needed price stability.

Many growers are faced with the conundrum of what and when to plant. Most seed probably has around six weeks to break through before emergence issues can occur, but at current temperature this could easily be exceeded. Growers need to remember problems that showed with some varieties last season, both with emergence and little potato disease.

A lot of this was caused by anaerobic conditions in the ridge, but we are currently >3C colder than last season and could, in some cases, be planting 50% more small seed fractions that have less vigour and reserves. I would usually say 6C and warming as the lowest temperature to plant. Worryingly though, it has been dry in Scotland for 2 weeks and history suggests we miss dry planting windows at our peril, warmer often meaning wetter.

Early set skin needs to go in and last week some growers made a start on main crop. There is no rush for seed until conditions improve, even if that is the end of the month. Risks need to be managed for ware crops. Do not force any crop in to cold, wet soil as this is a recipe for disaster. Planting any varieties with known emergence problems < 8C is seeking trouble.

While Maris Piper, King Edward,  Marfona and  Markies are likely to come to little harm, planting Saxon or Vales Sovereign and Estima is likely to result in emergence issues. Make sure seed is no warmer than the soil it is going into hence, at present, planting out of cold store is probably best in order to avoid seed being cold shocked back into dormancy which leads to further  issues. Growers need to plant no deeper than necessary. Planting at 20cm does not result in any less greening than 15cm.  

Prolonged emergence means crops are more susceptible to both soil borne rhizoctonia and Free Living nematode feeding damage. On light soils, where these are known to be an issue, there is likely to be a response to in furrow fungicide (azoxystrobin) in combination with application of a nematicide.

The cold soils may also mean we could see a lot of symphilid damage. Though not seen in coastal areas for a number of years, this will also hopefully be controlled by nematicide.

Let’s hope for a heatwave at the end of April and early May – we may need it.

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