Soil testing

Testing Dairy Farm Soil for DDT

DDT analysis is performed on Dairy Farm soil in order to determine whether it is present and if so, at what level

About this Testing

DDT analysis involves looking for four main compounds out of the six associated with DDT.

The target compound during manufacture was 4,4'-DDT, however the 2,4'-DDT isomer was an unintentional by-product comprising around 10-20% of the total DDT content.

In the environment, DDT breaks down to DDD, then DDE. So the total DDT content of a soil sample should include the sum of six compounds (4,4'-DDT, 4,4'-DDD, 4,4'-DDE and their corresponding 2,4'- isomers). However, because the 2,4'-isomers only comprise a small percentage of the overall total, the 2,4'-DDD and 2,4-DDE isomers are not included when analysing for total DDT.


Fonterra Limit (mg/kg dry wt)




By-product from the manufacture of 4,4'-DDT, usually 10-20% of 4,4-DDT value



Breakdown product of 4,4'-DDD



Breakdown product of 4,4'-DDT



Target pesticide

Total DDT


The sum of the above isomers

Reasons for using this test

DDT is an Organochlorine pesticide which was applied in pelletised form to agricultural pastures to control grass grub from the late 1940's until 1970, when it was banned in New Zealand . Concern over the environmental persistence of DDT, alleged carcinogenicity and observed bio-accumulation and magnification in the food chain led to its ban for agricultural use worldwide.

Dairy cows ingest DDT contaminated soil during grazing. In the cow's stomach, DDT is removed from the soil and converted into DDE before accumulating in fatty tissue and milk.

In addition to human health concerns over DDT and its isomers, farms producing milk with elevated DDT levels suffer financial penalties and for this reason it is imperative that new farms are tested for DDT prior to conversion to Dairy.

Taking a Sample

Sampling for DDT in soil from Dairy farms is very similar to nutrient and mineral with the following exceptions:

  • Farms converting from sheep and beef (or other farming types) to dairy that will be used to supply milk to Fonterra must use a Fonterra approved tester.
  • A 1.5 inch (37.5mm) soil auger must be used for Fonterra supply
  • For all other applications, a 3 inch (75mm) soil auger may be used.
Unsure about the correct container to use to submit a sample? Consult our container catalogue


Sampling equipment

  • 75mm (1.5 inch) or 150mm  (3 inch) soil auger
  • Sampling bags (request a DDT soil kit from the lab)

Guides & Supporting Information

List of Approved DDT testers:

    • Please contact the lab for approved samplers in your area.

    Contact Us

    Freephone 0508 HILL LAB (44 555 22) or email