Control of Potato Cyst Nematodes: Consultation on the Implementation in Scotland of Directive 2007/33/EC

3. Soil sampling rates and criteria

Standard and reduced rates

14. The 2007 Directive sets a standard sampling rate for official pre-crop soil testing for PCN of 1500 ml soil per ha. This is to be collected from at least 100 cores per ha, preferably in a rectangular grid not less than 5m in width and 20m in length between sampling points, covering the entire field. The entire sample is to be used for analysis.

15. The sampling rate can be reduced to a minimum of 400ml/ha for fields where:

a. There is documentary evidence that no potatoes have been grown for 6 years before the test; or
b. No PCN have been found in the previous 2 official tests; or
c. No PCN or dead cysts have been found in the most recent official test.

(b) and (c) will not apply if any potatoes that were not themselves grown on PCN tested land have been planted in the field since the most recent test or, for (b), since the first of the two tests. Tests carried out under the current SPCS rules will count towards qualification for the reduced sampling rate for as long as they remain relevant.

16. The adoption of a flat rate for soil sampling would result in the testing of more soil from larger fields and would lead to a greater chance of detecting a similar underlying distribution of PCN in a large field than in a small field. In recognition of this, a further reduction is permitted for large fields:

• For the standard sampling rate, the first 8ha shall be sampled at 1500 ml/ha, with each additional hectare sampled at a minimum rate of 400 ml/ha;
• For the reduced rate, the first 4ha shall be sampled at 400 ml/ha, with each additional hectare sampled at a minimum rate of 200 ml/ha.

In each case the average sampling rate is calculated and applied across the whole field. So for example, a field of 11ha would be calculated as follows, for the standard rate and for the reduced rate:

11ha at standard rate	11ha at reduced rate
8ha @ 1500 ml = 12,000ml	4ha @ 400ml = 1600ml
3ha @ 400 ml = 1200ml	10ha @ 200ml = 1400ml
Total soil required = 13,200ml	Total soil required = 3000ml
Average rate = 1200ml / ha	Average rate = 273ml / ha

(In practice the amount of soil taken will be rounded up to allow inspectors to take a whole number of standard-sized samples).

Impact on soil sampling in Scotland

17. The current standard rate of pre-planting soil sampling for PCN in Scotland is 600ml for an area up to 4ha. If the standard rate in the 2007 Directive of 1500ml per hectare was applied to all land currently tested, it would result in a ten-fold increase in the amount of soil tested. This would impose a significant burden on growers and would probably exceed the capacity of current testing resources, both staff and laboratory facilities. Fortunately, however, much of the land used for production of seed potatoes in Scotland will qualify for sampling at the reduced rate. A very high proportion of land which has been tested under the current arrangements has a documented history of freedom from PCN. In addition, the majority of basic seed potatoes are grown on rotations of one year in seven or longer. It is estimated that only around 5% of the land currently tested each year would require to be sampled at the standard rate.

18. In 2006, 17,461 ha were tested, taking 3404 litres of soil in total. SASA has calculated that, if all that land qualified for the new reduced sampling rate, and no account is taken of larger fields, at least 6985 litres of soil would require to be tested. Some additional sampling will be required to cover farm saved seed, however this figure can be used as a baseline for further calculations.

Definition of a field

19. Member States have freedom to define a "field" for the purposes of the PCN Directive. This is the area from which a single soil sample will be taken - cores may be placed in several sample bags for ease of processing, but they will not be identified as coming from separate areas and a single result will be given for the whole "field". If PCN are found in the sample, restrictions will also apply to the whole area. The equivalent under current arrangements is the 4ha unit - fields larger than 4ha are split into 4ha sections for soil sampling, and fields smaller than 4ha may not be divided. Sampling across a larger "field" allows a lower sampling rate to be used, which would generally be an advantage for both growers and RPID. However, this also carries the risk that a larger area will be taken out of production if PCN are found.

20. The most obvious definition of a field is an area surrounded by recognisable boundaries - fences, dykes, hedges, ditches. This is the unit to which a field identification ( FID) number is given. However, at present seed potato growers are not required to have the entire field sampled. In 2006 the average size of field in which classified seed potatoes were grown was 9.6ha, but the average field area submitted for sampling was 8.5ha. We do not intend to require whole fields to be sampled, since this would create an unnecessary additional burden. We therefore have to consider whether any restrictions should be placed on dividing fields for soil testing.

21. In the case of the reduced sampling rate, for which most seed potato land in Scotland will qualify, the further reduction applies to fields larger than 4ha. The average size of a potato field in Scotland, between recognised boundaries, is between 8 and 12 ha. A very small number of fields are larger than 20ha. Calculations based on the 2006 data show that if the whole area tested in 2006 was sampled in future in 8ha units, this would achieve a 21% reduction in the amount of soil to be taken. 10ha units would give a 24% reduction, while sampling the whole area submitted for testing would give a 27% reduction. The results are presented graphically below:

22. The Directive would permit fields to be split into units smaller than 4ha for sampling. However, we consider that such small areas would be difficult to map and sample accurately. Since smaller areas bring no reduction in sampling rate, we are minded to retain the minimum of 4ha for part-fields. Part-fields should preferably have recognisable boundaries on at least 2 opposite sides, and the direction of drilling should be from one boundary to the other. However, these requirements may be waived with the agreement of RPID, depending on the topography of the field.

23. Taking into account the issues set out above, the following options are proposed for defining a "field" for the purposes of PCN soil sampling:

a. No part fields allowed: the complete area submitted for sampling. Parts of the area within recognisable boundaries may be excluded from sampling, but the sampled area may not be subdivided.
b. Units of 10ha. Large fields must be divided into sections as near 10ha as possible, fields smaller than 10ha may not be divided.
c. Part-fields to be determined by the applicant: no maximum size, minimum of 4ha.

24. Option (a) would give the lowest sampling rate in all cases and would be the simplest option in practice. Option (b) aims to achieve the optimum balance between sampling rate and the area on which restrictions may be placed, based on the average size of fields in Scotland. Option (c) gives growers the maximum flexibility to choose the size of units to be tested, however, this option would be the most complicated to implement and is likely to result in a higher overall sampling rate than other options.

Question 1: Which option do you prefer for the definition of a field?

Documentary evidence that no potatoes have been grown

25. In order to qualify for the reduced sampling rate, documentary evidence is required to prove that no potatoes or other host plants have been grown in the field in the previous six years, or since an official test which found the field to be clear of PCN. The Scottish Government holds a range of records which should be able to provide this information. Primarily, the location of all classified seed potato crops is recorded through the SPCS, and all ware (or farm saved seed) crops are required to be notified to SASA on the PP1 form, under the Plant Health (Potatoes) (Scotland) Order 2006. Failure to notify a potato crop is an offence; inspectors will record any undeclared crops which they discover and further action may be taken against the grower. It can therefore be assumed that these records will be complete, and that if no potato crop is recorded for a particular field, no potatoes have been grown there. On receipt of an application for PCN soil testing, RPID officials will search the SPCS and PP1 records to check whether the field is eligible for the reduced sampling rate.

26. The requirement to notify ware crops came into operation for the first time for the 2007 growing season, and will not therefore provide a long enough record when the new Directive comes into force for the 2011 growing season. In the meantime, RPID will make use of whatever records may be available from SPCS, ware inspections etc. Ad-hoc queries may also be made to IACS (Integrated Administration and Control System), used for applications for Single Farm Payments and other grants and support schemes.

Question 2: Do you agree with the proposed method of obtaining documentary evidence that no potatoes have been grown? Are there other records that should be considered?

"Banking" of test results

27. Until 2007, SPCS allowed PCN test results to be "banked", remaining valid for 4 years from the date of the test. This recognises that any PCN populations in a field will normally decline if no host plants are grown, although retesting is necessary after a time to check that PCN have not been introduced from elsewhere. In order to manage the changeover to a new testing regime, banking is currently being restricted, so that the results of tests carried out in 2008 and 2009 will not be valid beyond 2011. We are considering whether the banking system should be continued or modified under the new regime.

28. Four years has to date been considered a reasonable period for the banking of PCN test results, balancing convenience for growers with plant health protection. However, the great majority of crops are grown within 2 years of testing. For crops grown in 2007, the date of PCN testing was as follows:

Year of testing	Percentage of crops grown in 2007
2004	2%
2005	7%
2006	20%
2007	71%

On the other hand, under the new regime a longer banking period could allow large fields to be sampled more economically; for example, a grower with a 40ha field might wish to have the whole field sampled as a single unit in one season, and grow 10ha in each of the following 4 years.

29. We would welcome stakeholders' views on the following options for banking test results from 2010 onwards:

a. Return to 4-year banking;
b. Reduce banking to 2 years;
c. Remove banking and require all tests to be carried out in the same year as planting.

Question 3: Which option do you prefer in relation to banking of PCN test results?

30. SPCS rules require minimum rotation periods to be applied for different grades of classified seed potato crop. A field can be tested for PCN before the rotation period has elapsed. In this case, if it has tested clear of PCN and will become eligible for growing seed within the banking period, it will be marked as "Pass for [year]" showing the year from which it will be eligible.

31. The 1969 Directive required only that "an official investigation" should recognise fields used to produce "seed potatoes intended for marketing" as free of PCN. SPCS rules state that this official investigation should take the form of a pre-planting soil test, but exemptions have occasionally been made, allowing post-planting or post-harvest testing in exceptional circumstances. The 2007 Directive prescribes that the official investigation must be carried out pre-planting, therefore no exemptions will be possible under the new regime.

Survey of ware land

32. An official survey for PCN must be carried out annually on at least 0.5% of all land on which ware potatoes have been grown in that year, and the results notified to the European Commission by 1 April each year. The sampling rate required for this survey is at least 400 ml/ha. If PCN is found as a result of testing for this survey, the same measures will apply as for a field found infested through pre-planting soil sampling, and any potatoes which can be traced back to that field will be subject to restrictions. We anticipate selecting fields for the survey in late summer and carrying out the sampling the following February / March.