Escape from Phytophthora by advancing the potato crop

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16 Jan 2009
Unit: Praktijkonderzoek Plant en Omgeving

 The chance of Phytophthora infestation is lower early in the season; there is less foliage and the fungus has hardly developed; this decreases the chance of infestation of an early crop which in turn increases the chance of a good organic potato yield.

In a field experiment in 2008 at PPO AGV in Lelystad scientists of Wageningen UR investigated the separate contribution of different advancement measures to yield increase and quality improvement of the fairly late potato cultivar Agria. Supermarkets like this cultivar because of its good taste, even if Phytophthora forces early destruction (by burning) of the haulm. Foliage of Agria is susceptible while the tubers are somewhat less susceptible to Phytophthora.

All seed potatoes for this experiment have been pre-germinated from 14 March. Because this is usually standard practice in organic cultivation this has not been taken as an experimental factor in this field experiment.

The experiment was carried out on a clay soil (appr. 30% clay particles) after canning peas as preceding crop. Part of the field was fertilized beforehand with 120 kg N per ha in the form of feather meal granules whereas another part was not. Tubers were planted on two dates (17 and 28 April). After a few days the plots of both planting times were covered with sheet with 10% perforation. This sheet was removed at the end of May, foliage was burned early July, and the plots were harvested at the end of July.

Early planting was found to have a positive effect on tuber yield. The effect of extra large seed tubers 50/60 mm (instead of 35/40 mm) was even stronger. And nitrogen fertilization with feather meal granules in particular had a clearly positive effect on tuber yield. Fertilization with 120 kg N/ha, on the other hand, reduced the average under water weight of the harvested tubers.

This year, with its relatively late planting date and warm May, the temporary cover of the crop with a transparent sheet had no significant effect on tuber yield.
The combination of relatively early planting (mid April), large seed tubers (50/60 mm) and sufficiently high nitrogen fertilization (120 kg N/ha) resulted in a yield increase of 14 t/ha in this field experiment.
Source: www.syscope.nl

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