Executive Summary
What the report is about
This report summarises the results of studies leading to an agronomy of the seaweed Gracilaria chilensis in saline groundwater evaporation basins. An understanding of seaweed farming, physiology and nutrition is based on the existing literature, which is reviewed in this report. There is an enormous difference between monitoring seaweed growth in a glass aquarium and in a basin excavated in the soil of a salt affected paddock. Not only is there an increase in scale but there are chemical dynamics between soil, saline groundwater and a range of environmental variables that cannot always be predicted. This report is about the field trials for seaweed cultivation in saline groundwaters where the goal has been to achieve a growth rate of Gracilaria greater than 3% per day.

Target audience
The research was done to assist those farmers disadvantaged by saline groundwater and to enable them to consider these waters as a resource for a crop that can be cultivated in saline water. Although the report could be used by academic agricultural scientists to gain some appreciation of the issues and problems of seaweed agronomy, it is primarily written as a tool to interest and inform farmers who are seeking some hopeful news about their salt affected paddocks. The results have not been sufficiently conclusive to provide a manual of seaweed cultivation in inland saline waters but do show that the agronomic principles being developed for seaweed crops that could make currently degraded lands productive again using saline groundwater as a resource.

Background
Studies of the physiology and nutrition of seaweeds have shown that despite the specialised environment in which they live, most of the macro-algae (as seaweeds are more precisely called) require the same basic mix of nutrients and have the same metabolic processes as the terrestrial crops upon which we depend for our traditional grains. Only some of the mineral concentrations vary.

Seawater is essentially the same all over the world and contains all of the elements necessary for growth and maintenance of marine plants. The chemistry of saline groundwater, on the other hand, varies in each aquifer depending on how long it has been underground, it’s history and the types of rock and soil with which it has been in contact. In the Murray River basin where the ground waters are essentially marine, recent geological history has modified these ground waters and many of the changes in mineral concentration of the salts are beyond the physical or bio-chemical ability of the plants to respond favourably with sustained growth. High concentrations of particular salts are toxic to the macro-algae, even where the total salinity is within the plant’s range of viability.

Objectives
The specific aim of this research is to develop an agronomy and associated technologies for the cultivation of of Gracilaria seaweed so that the cropping of this marketable species could be introduced into regions where saline groundwaters have degraded farmland in Australia.

The major beneficiaries of the research are expected to be farmers who currently have salinity problems and need a crop to substitute for the loss of traditional crops on their salt-degraded land. The production of seaweed could enable farmers to take advantage of our saline groundwater resources to produce export crops worth more per hectare than the current suite of grain crops. Gracilaria would be dried and exported in bales at $500-1000 per tonne to processors for the production of agar gel, which has a growing international market as an additive in the food and biotechnical industries and takes more than 35,000 tonnes of dried Gracilaria per annum.

Methods
The selection of Gracilaria chilensis as the species for cultivation was based on its large world market for the extraction of agar. Several varieties and eco-types of the Gracilaria were used in this study and one type was selected for its wide salinity tolerance, high gel strength and good growth compared to other eco-types of this seaweed.

Due to wide variations in the chemical composition and salinity of the groundwaters between catchments and between irrigated and dryland salinity regions, four sites in Victoria were selected for field trials: two irrigated salinity sites at Girgarre and Lake Charm and two dryland salinity sites at Jeparit and Donald. The waters in these trials were indeed dissimilar, the Jeparit being unable to support Gracilaria because it was too rich in iron and others requiring supplements of potassium necessary for plant survival.

Results/Key findings:

• The outcomes achieved have not yet established a new paradigm that saline ground water can be used as a productive agricultural resource to provide a new income stream for farms that have lost the ability to harvest traditional crops from salinsed land. Pilot trials in small on-farm evaporation basins have begun to establish the base line requirements and preliminary growth rates for the seaweeds in inland saline groundwaters. If the methods become commercially viable, seaweed harvests could mitigate the costs of engineering investments and operating costs for salinity rehabilitation programs as well as providing a profitable new export crop for Australia.
• Whilst commercial quantities have not yet been harvested, sufficient evidence has been collected to support detailed seaweed physiological studies and encourage further field trials that can lead to sustainable and profitable cropping of Gracilaria seaweed.
• There is a limited range of chemical composition of the saline groundwater medium in which Gracilaria will flourish, with a baseline of “normal” seawater. Either critically limiting nutrients or a super-abundance of certain minerals will result in the death of the plant in an active process of chemical transfer.
• Growth rates in appropriate groundwaters have only reached an unsustained 2.5% per day, far lower than the potential shown in the literature.
• Until now seaweed agronomy research has been structured around field trials that might have  been immediately transferable to farmers but the results have been disappointing and suggest that the scientific literature consulted was not a sufficient basis for the proposed development.

Implications:

• The profitable and productive use of saline groundwater could provide a chance to recover lost income where farmland and infrastructure are being degraded by salinisation of soils.
• The export market for seaweed has a potential value to farmers measured in the tens of millions of dollars
• A factory to extract gel or add value to the product could possibly be established in small communities to increase employment and support spin-off industries.
• Whilst commercial quantities have not yet been harvested, sufficient evidence has been collected to support detailed seaweed physiological studies and encourage further field trials.

Recommendations
Seaweed cultivation in inland saline groundwater still has agronomic potential; and future research and development is required to understand the limitations of our current systems.

A systems research approach is recommended, including hydro-geology, agronomy, water chemistry and soil-water interaction, extension, engineering and business skills to develop technologies, agronomy and models for profitable cropping of seaweed in saline groundwaters.

Seaweed physiology, photosynthesis and diagnostic information on seaweed nutrition needs to be studied in the laboratory. Results of seaweed growth trials under laboratory conditions would inform field trials.

There is a need to maintain focus on closely managed field trials at salt-degraded farm sites at Donald and Lake Charm (Victoria) and Morawa (WA) that involve farmers at the earliest stages of technology development to establish reliable agronomic protocols for crop and water management that maximise both growth and gel quality of the harvest.

Agronomic models should consider the whole of the value chain, starting with the market demand for raw material and moving backward to plan harvests for seaweed gel quality and yield that best meet market needs.
 

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