New seed rate guidelines taking account of the importance of tuber size to the value of potato crops for the variety Estima will be extended to other important varieties within the next year.
Data had been gathered for other varieties, such as Maris Piper, Maris Peer, Hermes and Saturna, David Firman of Cambridge University Farm told a seminar at British Potato 2007 in Harrogate. “The principles are the same for other varieties, but the responses will be different.”
The new guide for Estima moves recommendations on from the previous approach of just optimising yield from ware production to also taking into account tuber size.
That would help maximise the value of the crop through increasing yield of the desired size, he explained.
Another advance was the guide took into account the effects of seed age. Seed age – measured as the period from emergence of the seed crop to the planting of the ware crop – influenced the numbers of stems produced and hence the numbers of tubers and their size, he said.
Using the guides
That information could be used to influence tuber size distribution, he explained. For example, lowering stem populations would increase mean tuber size for a given yield.
Using the guide required following four steps, he said. The first was to determine the seed age – information seed suppliers should be able to provide. Different recommendation tables are provided for three different seed ages – early, standard, and late seed. Recommended plant populations are lower for early emerged (older) seed, and higher for late (young) seed.
Next growers needed to determine what tuber counts were available to them, he said. That would determine which row on the table to use to determine plant density and seed rate.
Step three was to determine target yield and optimum tuber size, which field history and experience would help decide. The Estima guide offered recommendations for yields between 45-70t/ha for a mean tuber size of 60mm.
Some recommendations could result in plant populations of less than 25,000/ha to produce the desired crop, he noted. “These areas are shaded red on the table, and are not normally recommended. Planting at wide spaces can result in unacceptably gappy crops and yields could suffer.”
Growers looking for a high proportion of large tubers at low yields (e.g. 60mm mean size at 45t/ha) should look to use late-produced seed. Only a small fraction of early produced seed and standard seed with a tuber count of over 700 could produce these crops without using very low seed rates, he noted.