Variable – is the word that best describes the potato crops that I see across the northern part of the country. Speaking to others it seems to be a similar picture wherever you are in the UK, which is unusual as in most years one or two regions have more favourable weather and as a consequence are often able to make up for supply shortfalls. This is not the case this year, as the whole country seems to have been under the influence of the jet stream.

I was once told that to grow potatoes successfully one needed to get the fundamentals right, chiefly seed quality and cultivations. If one or both are compromised then we all know that it is likely to be an uphill struggle to maximise marketable yield, so much relies on sunshine and adequate water.

This year seed quality has been variable, with Blackleg being the main issue, not helped by the extended planting period, cold dry soils followed by warm and wet soils. Compaction can be found easily, soil erosion and slumping is common place, all having an influence on the crop we are seeing now. Tubers have formed high in the ridge profile and as the soil dries it cracks open and greens become a big problem. Growth cracks are also a problem more often where soils have been waterlogged at some stage.

As mentioned earlier, sunshine and adequate water have a major influence on yield, assuming everything else is right. In 2011 most potato crops had achieved full canopy ground cover by the longest day in June, whereas only a few crops were in a similar position this year.

Met Office data says that for the months of June, July and August in 2011 there was 510.7 hours of sunshine across the main potato growing areas of East and North East England, compared with 410.8 hours for the same period this year. Rainfall for the months of June, July and August in the same area for 2011 amounted to 228.7mm, compared with 331.3mm for the same period this year. No wonder yields are down.

Tuber numbers are generally good, but size is likely to be limited with a shortage of bakers reported in packing crops. Wastage in crops will be a big factor and not just the obvious issues that can be seen easily such as greens, growth cracks, powdery scab and rots. But I am also seeing hollow heart and spraing, which are not seen until tubers are cut. Dry matter also seems to be on the high side so bruising may become an issue, particularly later in the harvesting season when soil and tuber temperatures drop.

Growers will need to make some really crucial decisions over the next couple of weeks about what to store and what not to store. Is the crop in a fit state to store in the first place, how do you know? I encourage growers to take representative sample digs from each field and carry out a simple analysis of yield and quality, involving buyers at this stage is useful so that there are no surprises, it also gives the grower an idea of the storage space required, crucial when planning the filling of stores and ventilation.