What This Means If You Grow Hayward Kiwifruit
This trial was run on a commercial Hayward kiwifruit orchard at Paengaroa, near Te Puke – a site considered the global optimum for kiwifruit production. Two equally matched one-hectare blocks were selected. One received AgriSea seaweed treatments; the other did not. Everything else was identical. The result: seaweed-treated vines produced significantly heavier fruit, larger leaves, and a measurably higher return at the orchard gate. Fruit from the AgriSea-treated block averaged 91.7 grams compared to 85.45 grams for untreated fruit – that's 6.25 grams heavier per fruit, and a statistically highly significant result (p=0.010). At orchard gate returns, the treated block earned NZ$3,019 more per hectare.
7.3% Heavier Fruit at Harvest
Individual fruit weight increased from 85.45g to 91.7g – a 7.3% gain that is statistically highly significant (p=0.010). Heavier fruit means better grading outcomes and higher returns per tray.
Fewer Rejects, More Grade 1 Fruit
The treated block's reject rate was 0.44% lower than the untreated block. Smaller fruit that would otherwise fail grade one criteria was reduced – directly increasing the proportion of premium-grade fruit.
6.4% Larger Leaf Area
Treated vines produced leaves averaging 189.8 cm² vs 178.4 cm² for untreated vines. Larger leaves intercept more light, boosting the photosynthetic capacity of the whole vine.
NZ$3,019/ha More at the Gate
Using 2007/08 orchard gate return values, the treated block returned NZ$34,300/ha vs NZ$31,281/ha for the untreated block – a clear economic advantage from seaweed treatment alone.
Fruit Weight Results
Sixty fruit samples were collected from each treatment area one month before main harvest by Ag-first Ltd following standard non-biased protocols. Full bulk grading data was also captured at the grader for each block separately.
Individual Fruit Weight Comparison
60 fruit sampled per block – one month pre-harvest
Whole Block Average Fruit Size (Grader Data)
Full-block mechanised grader results
No significant differences were found in fruit dry matter or brix at this pre-harvest sampling date, likely due to fruit immaturity at time of collection. Fruit weight, however, was highly significant.
Leaf Size & Shape – A Hormonal Effect
Sixty leaves were harvested from each block and measured for length and width. The treated vines produced leaves that were significantly larger – but the increase was in length rather than width, altering the overall leaf shape. This pattern is consistent with a hormonal (cytokinin) response, not a simple nutrient effect.
(length-driven, p<0.001)
Leaf Length Comparison
Treated leaves were 6.2% longer – driving the overall area increase
The leaf shape change mirrors the effect of naturally produced plant hormones already known to control kiwifruit leaf morphology. AgriSea's cold-fermented Brown Kelp (Ecklonia radiata) retains active cytokinins and auxins (IAA, IBA) that are typically destroyed in heat-processed products – making the hormonal mechanism highly plausible.
Why Does It Work?
The leaf nutrient data, when analysed using Compositional Data Analysis (CODA) with isometric log ratios (ilr), revealed that treated vines had enhanced photosynthetic efficiency. Rather than feeding the plant more nutrients, seaweed appears to help the vine use what it already has more effectively.
Hormonal Activation, Not Just Nutrition
The increase in leaf size was not accompanied by increased leaf nutrient content – ruling out a simple fertiliser effect. The cytokinin and auxin compounds present in cold-fermented kelp are the most likely mechanism.
Greater Photosynthetic Efficiency
CODA analysis (ilr 12) showed treated leaves had a significantly lower nutrients-to-filling ratio – meaning more of the leaf's dry weight came from photosynthetic products (sugars, cellulose) rather than mineral nutrients. The vine was photosynthesising more effectively.
Cold Fermentation Preserves Bioactivity
AgriSea's Brown Kelp (Ecklonia radiata) is partially beach-dried then cold-fermented in Paeroa. No heat is applied, preserving the activity of cytokinins that are typically destroyed in other seaweed products.
Larger Canopy = More Energy for Fruit
A 6.4% increase in leaf area means more light intercepted and more photosynthate produced per vine. This additional carbohydrate supply is the most direct explanation for heavier fruit at harvest.
The Trial & The Economics
The trial was conducted with rigorous commercial controls at Longridge Orchard, Paengaroa, during the 2007/2008 season. Treatment and untreated blocks were harvested separately with grading conducted by a mechanised fruit grader.
Treatment Programme
1× soil application October 2007. 3× foliar sprays at 5L/ha in 1,000L water (7-day intervals, post petal fall)
Trial Location
Longridge Orchard, Paengaroa. Near Te Puke, NZ. Two 1-hectare blocks, similar history
Orchard Gate Return
+NZ$3,019/ha treated vs untreated (2007/08 values)
Seaweed Treated: NZ$34,300/ha | Untreated: NZ$31,281/ha — The advantage from using AgriSea seaweed products was more than NZ$3,000 per hectare – from a treatment programme costing a fraction of that.
About the Research
This trial was planned, coordinated and analysed by Bio Soil & Crop Ltd NZ (Philip Barlow). AgriSea Ltd supplied the seaweed products – Brown Kelp (Ecklonia radiata) cold-fermented at Paeroa, Waikato – and funded leaf lab analysis. Fruit samples were collected and measured by Ag-first Ltd following industry standard protocols. Orchard gate returns were calculated by Steve Saunders.
The trial was conducted on a commercial orchard, not a replicated Latin square design. The authors acknowledge this and invite investors to support a fully replicated study. Despite this limitation, the fruit weight result (p=0.010) is statistically robust, and the economic advantage is clearly demonstrated.
Barlow, P.C. (2007/2008). Seaweed Application to Hayward Kiwifruit (Actinidia Deliciosa) Orchard Trial. Bio Soil & Crop Ltd, New Zealand. Trial partners: Stuart Steel Long-ridge Orchards; AgriSea Ltd; Bio Soil & Crop Ltd.