March has been a busy month for the Carbon Positive Project, and has included harvesting the tomato crop, finalising the plan for what happens after harvest, and planting our winter cover crops.
Hand Harvest
Yield was measured by both hand-harvesting sub-samples, and machine harvesting each plot individually. The hand measurements were taken from four 0.5 m x 2 m (1 m2) sub-plots in each plot. In all, over 650kg of tomatoes were picked by hand, graded into different colours (red, breakers, green, rots, vine) and weighed. Paid weight of fruit includes both the red and breaker fruit (anything that has a bit of colour in between green and red). Green and rotten fruit is considered out of spec and is not paid for. A team of eight people helped pick and grade tomatoes in the field, and we are most grateful for their support!
Machine Harvest
Once the hand sampling was completed, the Heinz-Wattie’s crew harvested each plot into its own gondola, which was tipped into its own bin (or two bins) and trucked to the factory to have factory quality assessment completed. The talented harvest crew carefully managed the task of coordinating the in-field harvest and the factory intake. Each bin entering the factory had a quality assessment completed. A sample is collected from the load, using a mechanical arm. The sample is sorted on reducing scales, taking off dirt, extraneous vegetative material (EVM), green fruit, rotten or damaged fruit, breakers and finally red fruit. This process determines what a grower will be paid per tonne after deductions. Plots had between 10.91MT and 16.39MT nett weight harvested (each plot is 0.108ha). After deductions, paid weight was between 92.32MT/ha and 142.66MT/ha, which is a great result.
Results
The hand harvest data found that the Conventional Treatment yielded 140.63T/ha on average, the Hybrid 148.98T/ha, and the Regenerative 93.42T/ha. There was no statistically significant difference between yield for the Conventional and Hybrid treatment, however there is a significant difference between these treatments and the Regenerative treatment.
The factory yields were slightly different to the hand harvest assessments. This is not unexpected, because hand-harvests measure only a very small part of the total paddock, and the machine harvester is unable to pick up all fruit, whereas hand harvests did. The factory quality sampling is also from a small random sample which has “errors”, although these even out over a whole commercial paddock. Average factory paid yield for the Conventional treatment was 134.6 MT/ha, Hybrid 129.3 MT/ha, and the Regenerative 95.1 MT/ha. One difference is that the factory quality assessments found a lot of soil clumps in a hybrid sample which added to the deductions. Note that the hand harvest data showed the Hybrid had the highest average yield, but in the machine harvest the Conventional came out on top, but both were “not significantly different”. You can see in the charts that both overlap in each case, so we are not confident the slightly different yields actually represent a true effect of our treatments. This is why we use statistics!!
As well as yield weights and fruit grading, samples were collected and analysed for brix, dry matter, Hill laboratory analysis (nitrogen percentage and carbon percentage) for both fruit and vine, and pesticide residues. Brix is a measure of dissolved solids in a liquid and is used to determine dissolved sugar levels. Heinz-Wattie’s analysed four subsamples per plot to determine Brix, finding the average for the Conventional Treatment was 4.88, Hybrid 4.89 and Regenerative 5.41. The brix level in the Regenerative treatment was significantly higher than the other two treatments. Higher brix levels correlate with higher dry matter, which for the Conventional treatment was 6.4%, Hybrid 6.5% and Regenerative 7.1%.
We have a lot more analysis of our tomato data yet to complete. We’ll be giving a rundown at the LandWISE Conference in Havelock North in May.
What’s Next
The tomato harvester finely chopped all the crop residues, which Mike Kettle buried using a set of heavy discs used to break up the beds after harvest. Gareth Holder followed up with a lighter set of discs to create an even surface. Mike’s team drilled the winter cover crops on the 22nd of March. The Conventional treatment has been planted in an annual ryegrass, which will be grazed over the winter. The Hybrid and Regenerative treatments, which will not be grazed, have been planted in a diverse cover crop mix containing oats, vetch, crimson clover, tillage radish, sunflowers and buckwheat. Patrick Nicolle did the final operation on 25th March, soil aerating to about 400 mm to try and shatter the tillage pan present across all treatments (more prominent in the Hybrid) and Cambridge rolling to reconsolidate the seed bed. We then applied 5 mm of irrigation to help the cover crops establish quickly. The Conventional and Hybrid treatments will be planted in peas for McCain Foods in early spring. All three treatments will be planted in beans for McCain Foods in December.
We have planted an extra area, outside the main trial, in cover crops so we can gain experience with cover crop termination in spring. We would like to avoid herbicides in the Regenerative treatment wherever possible, so our aim is to crimper roll and retain residues as a mulch. We think we can plant beans through the mulch but are unsure the crimping will fully kill the cover crops. The extra area will allow us to test options, including crimper rolling timing and the difference with and without chemical termination. Getting the timing right for a single species is one thing; getting it right for a five species mix is another thing entirely!
Carbon Positive is a partnership project between LandWISE and the Hawke’s Bay Future Farming Trust, with Heinz-Wattie’s, McCain Foods heavily engaged. Funding is from MPI via the SFFF fund, Hawke’s Bay Regional Council, Heinz-Wattie’s, McCain Foods, BASF Crop Protection, and Hill Laboratories.
