Root Phosphonate Testing
Sampling procedure for root phosphonate test:
•Avocado roots are soft and easily damaged.
•They will also decay very quickly if left to sweat in a bag.
•Phosphonate ion is easily leached and very water soluble.
•Be sure to detail method, timing and frequency of treatment
This is a first draft and subject to change as we learn/validate from field data
a.Root testing prior to phosphonate application will provide information on whether or not application is required at all. Combining the result of a pre-application test with a post application test can also provide information on the efficacy of the application method being used.
b.The timing at which point phosphonate levels peak in roots following application may vary. Factors such as application method, tree water use and overall tree metabolism may influence this timing. Preferably post-application root sampling should be carried out 5 weeks after treatment, but this timing is not critical as levels should persist longer and drop slowly from peak concentrations. Sampling should however be carried out during a root flush (spring or autumn) so that the majority of the sample is new white feeder roots from the mulch layer (pencil down to fine). This is because phosphonate will preferentially flow to the new root growth.
2. Representative sample: Take from a range of trees within a block and range of position around the tree. But keep tree age, health and history consistent.
3. Avoid delay: Sample on a Monday morning and courier immediately to Hills.Do not sample mid to late in the week. If necessary, root samples can be frozen before couriering at room temperature but samples should still be sent as soon as possible following sampling.
4. Damage/Decay/Dessication: Root sample must arrive fresh and undamaged. Avoid drying out, sweating in a plastic bag in the sun, crushing. Use as long sections of root as possible. Wrap root sample in kitchen towel/tissue and send in a paper envelope or ziplock bag.
5. Quantity: 10g to 50g as demonstrated
6. Leaching: Do not wash roots as phosphonate is extremely water-soluble.
Prepared by Jerome Hardy, Primor Produce Limited