Spud Special: Planting under way in Scotland

Growers are putting the worries of lack of demand in the fresh market and movement of pre-pack behind them and starting to plant. Planting of early set skin and salad crops has commenced in many regions. Ayrshire is particularly behind due to prolonged heavy rain up to recent weeks even preventing ploughing.
Soils temperature are good (7C or above) so once soils dry there should be no delays. This may be one of rare years where we see emergence in 3-4 weeks in Scotland, hence growers need to think carefully about late frosts when deciding when to start main crop planting.

It looks like a repeat of last season with soils wet at depth, but rapidly drying on top. This will need careful management in order to minimise compaction pans. The majority of land was ploughed in the excellent conditions existing during the autumn, but have slumped in places. Land being ploughed now is generally coming up drier and on light land is working better. There will be a big advantage to open land up with deep tine cultivator to dry it prior to deep ridging.

Level of Rhizoctonia on seed is very variable, but in general more than usual due to a late soil borne infection and prolonged period after desiccation waiting for skin set and stolon separation. Growers need to wash seed and check for black surf. While eye plug tests may reveal more Rhizoctonia present, black scurf presence is usually representative of the level of infection. Where <10% of tubers are infected a half rate pencycuron (Monceren) or full rate flutolanil (Rhino) should be applied. Where more Rhizoctonia is present the rate of pencycuron should be increased. Soil applied azoxystrobin does not adequately control seed borne infections of Rhizoctonia under high pressure so a seed treatment are going to be require this season in most cases.

Where eyes have opened on seed there is evidence that the heat and drought stress during growing may have run the physiological clock faster than usual as some stocks appear to have all there eyes open, even at the stolon end of tuber. If this is the case then some ware crops would benefit from reducing the planting density by approx. 10% to account for the potential increase in stem numbers. There is variability, so growers need warm samples and check the number of eyes that open for different seed batches.

All the evidence is that blackleg bacterial levels on seed are low this season, however, even low levels can rapidly multiply and cause a problem if seed is managed poorly prior to planting. If seed is delivered to farm more than a few days ahead of planting then it should be decanted into boxes and ventilated where possible. If it has to be left in bags then ensure the bags are on pallets and that air is blown through them. Never plant warm seed in cold ground. If you are planting in high temperatures then use seed out of cold store, though try to bring seed out of cold store into ambient an building no more than 4C warmer than the cold store to avoid condensation.

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