Cyclone Gabrielle silt study provides critical insights on recovery

A study examining the recovery of land covered by silt during Cyclone Gabrielle is providing critical insights on options to manage recovery.

‘The study was aimed entirely at growers and supporting their recovery, as well as the land’s. We found that land covered by sludgy clay-based silt could grow good vegetable and arable crops in the next season, with minimal additional effort. However, the story was considerably different for land covered by sandy silt. Crops grown on this land did not thrive,’ says Hawke’s Bay researcher Alan Kale who worked with colleague, Diana Mathers.

The study looked at the recovery of silt covered land at 34 different sites in Hawke’s Bay, Wairoa, Gisborne and Tolaga Bay. The study was managed by the Foundation for Arable Research (FAR) with funding from the Ministry for Primary Industry’s (MPI) North Island Weather Event Fund, and Vegetable Research and Innovation (VR&I). 

‘We’d like to thank all participating growers for their openness and willingness to give freely of their time and knowledge, at a time when they and their families were enduring extreme physical, financial and emotional impact,’ says Alan.

‘The whole idea of the study was to create a body of knowledge that could be used immediately, as well as in future similar flooding events. We believe we have achieved this outcome. However, we also believe that there is more work we could do to aid understanding, if there was funding to extend the study for another couple of years.’  

Initial conclusions

• Cropping on silted sites in the Heretaunga plains was very successful
• No extra pest and disease inputs were required. Some fields had an extra side dress applied, otherwise fertiliser practice was as normal
• Most sites grew and produced crops at or above normal pre cyclone levels, and current season non-silt crops
• Generally, growers were comfortable to return to normal cropping cycles on these sites
• The exception to the above is the sandy silt type sites
• Wairoa was unable to establish many crops due to the continual rainfall.

Note: weather conditions in the season following Cyclone Gabrielle contributed to strong regional differences in recovery. Wairoa and Gisborne/Tolaga Bay experienced a much wetter season than Hawke’s Bay and this resulted in numerous challenges and lower yields.

View a presentation

To view a presentation on the initial study, click here.

Hear Alan on Nine to Noon

Alan was interviewed by Kathryn Ryan on RNZ's Nine to Noon programme on 11 September. Click here to hear the interview.