Heniz-Wattie’s was unable to process our butternut through the factory due to a lack of demand, so we had to find an alternative outlet. A local grower ended up harvesting the butternuts on the 13th of March, which was a month earlier than our target harvest date with Heniz- Wattie’s.
Our butternut hand harvest of replicated plots was completed on the 9th and 10th of March. Four subplots of 6m2 were sampled from each plot. All butternuts within the sample area were cut from the plant, counted, and weighed. A butternut subsample was collected for Brix, dry matter, nitrogen, and carbon analysis. The plant residue was also weighed, and a subsample was collected for dry matter, nitrogen, and carbon analysis. Notably, although there are slight differences in the various metrics we assessed, none are significant at a 5% confidence level.
Butternut fruit yield
Yields were very high. We planted assuming 25 – 30 T/ha of butternuts but grew almost double that. The conventional treatment had an average yield of 52.74 T/ha, the Hybrid treatment had 52.00 T/ha, and the Regenerative treatment had 49.44 T/ha.
Butternut residue
The Conventional treatment had an average residue biomass of 20.57 T/ha, the Hybrid treatment had 20.25 T/ha, and the Regenerative treatment had 17.56 T/ha with differences again not significant.
Dry Matter
A subsample of butternut residue was dried to calculate the dry matter percentage. All three treatments had an average dry matter of 16%.
The Conventional treatment had an average dry matter of 8.44 T/ha, the Hybrid treatment 8.37 T/ha, and the Regenerative treatment 7.77 T/ha. While showing slight differences, these are again not significant differences between treatments (P>0.05).
Nitrogen percentage
The nitrogen percentage in the butternut plant residue was determined by Hill Laboratories. The Conventional treatment butternut residue had an average nitrogen percentage of 1.95%, the Hybrid treatment had 1.78%, and the Regenerative treatment had 1.70%.
To calculate the amount of nitrogen in the butternut residue, the dry matter (T/ha) was multiplied by the nitrogen percentage and converted to kg/ha. The Conventional treatment had 163.92 kg N/ha, the Hybrid treatment had 148.63 kg N/ha, and the Regenerative treatment had 131.97 kg N/ha.
Carbon percentage
The percentage of carbon in the butternut residue was determined by Hill Laboratories. The Conventional treatment had an average carbon percentage of 35.25%, the Hybrid treatment had 34.20%, and the Regenerative treatment had 35.50%.
The butternut residue dry matter (T/ha) was multiplied by the carbon percentage to get tonnes of carbon per hectare. The Conventional treatment had 2.95 T C/ha, the Hybrid treatment 2.86 T C/ha, and the Regenerative treatment 2.76 T C/ha.
Brix
To measure Brix levels, a subsample was taken from two butternuts from each sample area. The subsample was grated and squished in a garlic crusher, and the juice was tested with a Refractometer.
The Conventional treatment had an average Brix level of 7.1%, the Hybrid treatment 7.9%, and the Regenerative treatment 7.0%.
If Wattie’s had harvested the butternuts, Brix levels would have been assessed prior to harvest. Heniz-Wattie’s minimum brix level before harvest is 7%, ideally, they would be harvested between 9–10% brix. As the butternuts were harvested by a local grower approximately one month earlier than Heinz-Wattie’s standard harvest timing, the Brix levels were on the lower side.
Thanks, Phillip Schofield, Phillipa Page, Dan Bloomer, and Olivia Webster, for helping with the hand harvest.
A big thank you to all the Operation Advisory Group members who attended our weekly field walks throughout the season, providing us with their expertise and helping make decisions.
Carbon Positive is a partnership between LandWISE, the HB Future Farming Trust, McCain Foods, Heinz-Wattie’s and Process Vegetables NZ. Many thanks to our funders; MPI, Process Vegetables NZ, McCain Foods, Heinz-Watties and Hill-Labs.
