On-farm fermentation of sugar kelp seaweed to enhance seed establishment and to reduce powdery mildew progression

Summary

Two farmers and a viticulturist in Cornwall are working to reduce the use of fossil fuel based fertilisers on their farm, by using a novel on-farm fermented extract of sugar kelp (Saccharina latissimi). They will be trialing it both as a foliar feed and seed treatment to retain and improve crop productivity.

Sugar kelp, as opposed to widely-used Ascophyllum, can be sustainably cultivated throughout the UK, requiring no input and enhancing marine biodiversity, by creating floating reefs. However, the effects of a fermented extract on crops remain poorly understood due to the novelty of sugar kelp as an aquaculture industry.

The project will test the effect of fermented sugar kelp seaweed compared to a control on:

1)     Rate of establishment of autumn sown heritage wheat;

2)     Wheat plant vigour;

3)     Foliar disease progression on grape vines;

The second part of the trial will produce a seaweed ferment lifecycle assessment to determine its carbon footprint and cost.

The trial is being carried out with help from the Cornish Seaweed Company and Farm Carbon Toolkit.

Photo credit Caylon La Mantia

How it works

Seaweed extract is said to offer benefits to crops in terms of:

• seedling vigour
• crop quality
• disease resistance
• soil health
• carbon footprint

In terms of viticulture it is hoped that using seaweed extract on vines will combat some of the plant-health issues caused by the cooler, wetter and more humid British climate. These include mildew, mould, fungus, rot and other pest issues which can damage or even decimate vines and grapes.

Sugar kelp contains bioactive compounds that influence plant growth and health dynamics differently than the widely used Ascophyllum. The local provenance of the seaweed and collaboration with the farm group would offer the opportunity to determine the agronomic merits of home-produced seaweed extract.  

The novel element of this work is to use sugar kelp with bespoke on-farm equipment to de-centralise production, reduce costs and increase farm sustainability.

Trial design

Sugar kelp seaweed will be fermented with and without Bokashi in IBCs at Rosuick farm. There will be four treatments, two with bokashi inoculants and two without. A minimum of two months anaerobic fermentation will take place. 

Seeds will be assessed at timed intervals from; planting, 5 days, 10 days, 15 days and 20 days or until stable germination has been reached  Seed germination rates, root development and soil aggregate stability will all be assessed at the final germination time point.

Vine trial: The trial will have three treatments vines sprayed with (1) Bokashi seaweed ‘tea’ treatment 1; (2) Bokashi treatment 2; (3) Seaweed tea; and (4) water (control). The rates will be determined from phytotoxicity tests. Spray timings will be based on weather and humidity forecasting for powdery mildew.

Disease assessments will be based on assessing percentage mildew cover and % senescence on 10 fully formed leaves per treatment per block. Leaves will be randomly selected. Data will be transformed and then analysed by ANOVA.