The monitoring of DDT in New Zealand milk is universal. ACS are approved by Fonterra for DDT testing in soils. We are also able to advise on conversion suitability, or discuss farm management options to reduce the risk of milk contamination.
ACS Soil Residue Service
The ACS range of services will help you to:
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prove your land is free of DDT soil residue
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gain biological production status
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be able to offer your farm for conversion to dairying
Introduction
History
DDT, an organochlorine insecticide, was used extensively throughout New Zealand during the late 1950's and early 1960's as a control measure for Grass Grub and Porina Moth (at the caterpillar stage) on pastoral and cropping land.
Due to its persistence as a soil residue, and increasing evidence of damage to ecosystems in which it accumulated, it was banned from use on all pastoral and most cropping farms from 1969, although there was some use, under tight control, on very specialised situations (often amenity areas not involved in the food chain) until the 1980's.
From the early 1980's it became apparent that many of our overseas markets were becoming more aware of chemical residues contained in agricultural produce both from New Zealand and other supplier countries, and at that time some of our exporters, primarily in the dairy sector, instituted a pro-active campaign to position themselves as being exporters of produce falling within internationally recognised residue guidelines.
DDT field-sampling technique
Each paddock is sampled along three transects arranged in a "Z" pattern within the paddock, with an equal number of soil cores being collected per transect.
A minimum of 10 cores per transect are collected, giving a minimum sample size of 30 cores.
Each core is collected using a sampling tube set to collect cores 35 to 40mm deep.
(This approach was developed by Lincoln Ventures in association with AgResearch (then MAF Technology, South Central region) as the most cost-effective way to obtain a repeatable sample from a given area.)
Services Offered
ACS offer a wide range of services, designed to meet the needs of individual clients.
1. Indicative Testing.
A test protocol designed to collect samples and interpret results from small areas.
It is used to:
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Provide basic information, at low cost, to indicate whether a more comprehensive and expensive dairy conversion test is justifiable. Used for this purpose, a set of three or four samples per farm is collected. The outcome, while indicative, in no way guarantees that the farm will, or will not, be suitable for dairy conversion.
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Support the offer of off-farm dairy grazing. (Almost all dairy farmers now insist that the areas being offered for grazing have a recent DDT report.)
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Form a component of a farm sale portfolio. The number of tests completed is very dependent upon the size and type of property in question.
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Support an application for BIOGRO registration
2. Dairy Conversion DDT Tests.
The sampling of a farm, using the procedures for sample collection, submission and reporting as specified in the dairy company protocol, which is standard throughout New Zealand.
The Dairy Conversion DDT protocol is to be followed when the results are to be used to:
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Accompany a farmer's application to a dairy company as a prospective new supplier.
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Form a component of a farm sale portfolio being prepared by a real estate agent.
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Offer supporting evidence for a farm financing (or re-financing) application on non-dairy farms, as a low DDT status will often increase land resale value and so increase the owner's equity in the property.
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Provide supporting evidence in valuation reports on all farm types.
The Dairy Company Protocol
Fonterra dairy company in New Zealand has now adopted a common Soil DDT + Residues protocol. ACS consultants are recognised by Fonterra as being competent to carry out the field sampling protocols required for land intended for conversion to dairying and for land being offered for dairy grazing.
The soil samples taken for analysis are sent to accredited laboratories approved by Fonterra for the purpose of analysing soil DDT samples.
Indicative Tests:
Preliminary sampling.
Sampling is to be undertaken by an agent approved by the dairy company.
The Report:
The report will be:
i. A covering letter summarising the findings of the DDT survey
ii. The original of the Laboratory report.
iii. A copy of the farm map showing the paddocks from which the samples were taken
Interpretation
Land with over 0.700ppm DDT plus residues is generally considered unsuitable for dairying.
However, as preliminary indicative surveys only sample a relatively small portion of the property, the results are not to be regarded, or reported as, defining the suitability of a property for dairying.
Dairy Grazing.
Sampling undertaken to indicate the suitability of a property for off-farm grazing of dry or young stock is carried out following the same guidelines as Preliminary Indicative Testing.
Sampling is to be undertaken by an agent approved by the dairy company concerned. All samples are to be collected using a "Z" transect within the paddock.
Reporting:
The report will comprise:
i. A covering letter summarising the findings of the DDT survey
ii. The original of the Laboratory report.
iii. A copy of the farm map showing the paddocks from which the samples were taken
Interpretation
Land with over 0.700 ppm DDT plus residues is generally considered unsuitable for dairying.
Providing soil ingestion can be kept to a minimum - by:
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adopting on/off grazing in wet weather,
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using free-draining soils which are unlikely to pug and
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avoiding the use of root crops
- the risk involved in using soils with high DDT + residues levels may be acceptable to some farmers. The decision to accept land for off-farm grazing is therefore left to the farmer.
The role of the consultant is to report the levels found and draw the comparison between the measured levels of DDT and residues and the 0.700 ppm guideline, and outline the management practices needed to minimise risks associated with offering, or using, the land tested for winter dairy grazing.
Dairy Conversion
Land Area
The area sampled, and analysed, must be contained on a single, or combination of, complete Certificate(s) of Title. The client cannot arbitrarily decide to exclude various areas of the farm unless these are on, or going to be surveyed on to, a separate Certificate of Title, and physically isolated from the block being tested.
Paddocks
All grazeable paddocks surrounded by a permanent fence must be sampled separately. Occasionally paddocks on a title are encountered that are obviously waste ground, e.g. an un-drained swamp. These can be treated as waste ground and not sampled provided this is discussed with the client and they are clearly identified on the farm map as being unsampled. The area of these unsampled blocks is not taken into account when calculating a DDT Weighted Average for the property.
Farm Map
The client must supply an accurate farm map from which paddock areas, waste areas (to be excluded from the weighted average) and the total area of the titles from which milk is to be harvested, can be obtained.
If a farm map needs to be created for the proposed supply area, ACS can source the most recent aerial photographs for your area, and use these to draft a farm map for you to the standards needed by the Dairy Companies.
Indemnity Form
Your ACS consultant will sign an indemnity form attesting that all the required paddocks were sampled, and that the field protocols required by the Dairy Company, were followed.
Bulking of Samples
Sample bulking is carried out by the laboratory on the basis of 10 (ten) analyses per farm up to 300 ha, followed by a further 3 (three) analyses per 100 ha thereafter (this means, for example, that a farm of 400 ha will have 13 analyses, 10 for the first 300 ha + 3 for the extra 100 ha).
Your ACS consultant WILL NOT bulk samples in-field. The laboratory undertakes this task to ensure that mixing and grinding are carried out to a high degree of precision, ensuring that a completely homogenous sample is presented for analysis.
If there are less than 10 blocks on the farm being tested some sub-division of existing blocks will be required, which will be recorded on the farm map.
Note: If you want more than 10 analyses to be carried out, this can be done. Your consultant will tell the laboratory which samples are to be bulked together to provide the coverage you want.
Interpretation
The weighted average over the entire property must be no higher than 0.700ppm(w:w) total DDT plus residues.
No single bulk sample grouping can be any higher than 1.00ppm
Extension to Supply (Addition to Supply Area)
The Dairy Companies do not require that land intended for addition to supply be tested. However, as there are stiff penalties for excess DDT and residues in milk, they do recommend that a test, using the same protocols as conversion, is used to determine if a risk of contamination exists.
The Weighted DDT+Residues Average.
The weighted average is used in interpreting Dairy Conversion Protocol results because the total DDT intake by animals is proportional to both the amount of DDT and residues present on each block, and the proportion of total grazing time the animal spends there.
This is based on the assumption that, if a block forms 10% of the total farm area, then the animals will spend 10% of their time grazing there.
ACS have developed a spreadsheet, approved by the Dairy Companies, to perform this calculation.
