AGRE-0022 Development of Enhanced Quality Lipid Fertilisers Based on Naturally Occurring Seaweeds

Seaweed farming

SUMMARY

This project took a systematic look at the benefits of application of seaweed extracts as foliar sprays, which has been shown to be beneficial to a wide range of crops. Such extracts contain both trace elements and compounds with plant growth stimulating activity, which may produce a wide spectrum of effects including increased yield and quality, better seed germination and deeper root development. Use of such sprays have also been claimed to enable use of lower levels of chemical fertilisers and enhance pesticide efficacy, thus resulting in lower dose requirements with associated environmental benefits and reduction in production costs. This project established the potential value of such seaweed-based products in nutrient poor soils, through the development of a quality-controlled product which could be tested on a range of crops under various field conditions by independent experienced growers.

INTRODUCTION

Throughout Europe there is a need to reduce the use of chemical fertilisers in agriculture, horticulture and other land-use and to minimise the run-off of nitrate and phosphate from the soil resulting in pollution of water supplies. An alternative is to use natural products such as seaweeds, which have been used for centuries as fertilisers. More recently, the application of seaweed extracts as foliar sprays has been shown to be beneficial to a wide range of crops. Such extracts contain both trace elements and compounds with plant growth stimulating activity, which may produce a wide spectrum of effects, including increased yield and quality, better seed germination and deeper root development. Use of such sprays has also been claimed to enable use of lower levels of chemical fertilisers and enhance pesticide efficacy, thus resulting in lower dose requirements. Several seaweed extracts are marketed, the efficacy of which is variable. This project set out to assess the potential value of such seaweed-based products, through the development of a quality-controlled product which could be tested on a range of crops under various field conditions by independent experienced growers.

ACTIVITIES

A series of analytical studies of Laminaria hyperborea were used to establish factors which could influence the quality of extracts in terms of their general chemical properties including macronutrient content, trace element composition and bioavailability as well as phytohormone levels including that of cytokinins and betaines. Samples were collected in such as way as to minimise levels of potential interfering chemicals in extracts produced. A range of processing systems, which would retain the key active growth promoting compounds, was investigated and as a result a process plant was established by Orkney Water Test Centre (OWTC) Ltd for pilot scale processing. The seaweed used was collected by diver-based systems, designed to ensure a sustainable harvest. Quality control systems were established, including feedback from partners involved in trials, on all aspects of product use and performance. Three years of such field trials showed that the use of seaweed extracts produced a significant increase in yield with a range of crops, as well as resulting in other enhancements of crop quality. Cereals responded most positively, with oats producing the largest and most consistent increases in yield, followed by wheat and barley. Grassland usually responded well in the more limited trials conducted, as did carrots and red beet in most trials. Potatoes showed no significant enhancement with the main extract, although a copper enhanced extract produced good results with organic growers. Lettuce gave very contrasting results with good results shown by several Scottish growers as well as in routine OWTC product screening but no effects were recorded in the Netherlands trials. Fertility level of the soil appears to be important, with the largest increases in yield reported on sites with low fertility. It may be that the good growth found on high fertility sites tends to mask any effect of the seaweed extract. Plants growing on these sites also tend to be less stressed and so the ability of seaweed extracts to alleviate stress does not contributed to increased yields. As all soils in the Netherlands can be classified as high fertility sites, this may explain the lack of response in these experiments. High nitrates in vegetables are harmful to human health and in some crops there are legal limits of nitrates above which the product cannot be sold according to EU regulations. Treatment with seaweed extract caused reductions in nitrate levels in lettuce and potatoes, red beet and cabbage grown under conditions of high fertility. In root vegetables, high nitrogen levels also contribute to disease development and poor storage characteristics.

The mechanism for these responses is unclear although potassium in seaweed extract may be important. Potassium levels were increased in carrots with the use of seaweed extract and, in some cases, there were accompanying reductions in sodium. The trials programme was conducted using controlled, consistent batches of extract, yet it demonstrated the wide range of results shown in the literature, i.e. from no effect to strong positive effects. The variations reflect, therefore, differences in crop performance, under varying field conditions and extract application procedures. Soil fertility status and crop stress appeared to be particularly important factors.

EXPLOITATION PLANS

Further work is required to define a commercial scale seaweed harvesting system and to finally define the commercial product for agricultural field crop use. Commercial development of a product for horticultural use is already underway while further work has been carried out on the use of seaweed products in turf management. Trial marketing is underway.

PARTICIPANTS

Department of Ecological Agriculture, Wageningen Agricultural University (Netherlands); Orkney Water Test Centre Ltd (UK), TEAGASC (Ireland) and Farm Future (UK).