Broadscale production of wattleseed to address salinity
The water use of annual crops and pastures in the low and medium-rainfall agricultural zones of southern Australia is out of balance with rainfall, resulting in a slow filling of soils with excess water and, in many areas, a remobilisation of salt stored in the soil. As a result, large areas of the southern agricultural landscape are at risk of developing dryland salinity. The area likely to be affected in south-west Western Australia is estimated to be up to 30% (State Salinity Council 2000).
Of the many potential solutions to this problem, a key one is to reduce the leakage of rainfall past the shallow root zone of agricultural systems based on annual plants, by increasing the area of deeper-rooted perennial plants on farms (Hatton and Nulsen 1999). The extent to which perennial plants might be deployed in agriculture depends on the goal. Options include:
• slowing the rate of spread of salinity and delaying the onset of symptoms (least ambitious),
• halting the spread of salinity,
• reclaiming saline land (most ambitious).
The scale on which perennial plants are needed in order to control recharge also varies from place to place, due to hydrological variability and complexity. Where landscape relief is low, or soils have low permeability, lateral movement of groundwater is slow compared to the rate at which soil profiles are filling with excess rainfall.
potential and constraints GRAEME OLSEN Olsen & Vickery, PO Box 357, Waroona, Western Australia 6215
Edible Acacia seed or wattle seed, is a potential commercial crop that could provide land management benefits in low- to medium-rainfall agricultural areas in southern Australia. A review of wattle seed on behalf of the Joint Venture Agroforestry Program found that large markets for food ingredients are out of reach for existing wattle seed production systems, due to the high harvesting cost. Lowering the cost to a level competitive with other large-scale food crops will require development of a new production system that integrates crop layout, harvesting method and species election. An efficient harvester is likely to have many features in common with modern cereal crop headers: light weight, continuously moving, straddling the crop, and a wide intake to maximise the tonnage harvested per operating hour. Species best suited to such a harvesting system would be short, compact and erect, bear their seeds near the top of the plant, have a high ratio of seed production to vegetative growth, and be suited to growing at high density.
A plant with these characteristics would be very different from the tall, spreading shrubs currently used for edible seed production. A first step towards building a large-scale wattle seed industry would be to explore the abundant genetic resource of this genus for species with desirable characteristics for low-cost production. Leads to the conclusions that strategic placement of small areas of perennial vegetation would usually be ineffective in controlling salinity, and that a high proportion of the agricultural landscape (in some areas as much as 80%) would have to be revegetated to achieve that aim (George et al. 1999; Hatton and Salama 1999).
The National Land and Water Resources Audit (2001) gives a broad estimate of the likely need for perennial vegetation in agricultural areas: . for effective reduction in recharge there may need to be 30–50% reforestation in a catchment (and even more if trees are to be harvested).’ Based on this estimate, between 15 and 25 million hectares of perennial plants could be needed in southern agricultural regions. Such large-scale use of perennial plants in agricultural systems is likely only if the bulk of those plants have a commercial use (Bartle 2001) and produce financial returns similar to existing agricultural crops. Acacias are strong candidates for development into new perennial agricultural crops, as they have potential to produce a wide range of commercial products, including edible seeds.
Their favourable attributes include:
• large number of species,
• adaptation to Australian conditions,
• wide variability between and within species, enhancing the prospects for selecting suitable germplasm for commercial development, and
• potential to enhance nature conservation goals if appropriate species are planted in suitable locations.
development as crop plants and the range of potential commercial uses for Acacia are discussed elsewhere in this paper
Conservation Science W. Aust. 4 (3) : 185–191 (2002) Graeme Olsen
Edible Acacia seed or wattle seed is a potential commercial crop that could provide part of the perennial plant component of a new Australian agriculture. It has many attractive elements as a commercial crop:
• it has a long history of use by indigenous Australians as food (Devitt 1992, cited in Harwood 1994),
* a small commercial wattle seed industry is already in operation (Maslin et al. 1998),
• grains and seeds are high-value products that lose only a moderate percentage of their value in transport costs when transported long distances to markets,
• grain production and export is a familiar industry for Australian farmers, and
• an Australian grain handling infrastructure is well developed.
Maslin et al. (1998) reviewed the potential of Australian Acacia species for wattle seed production. Based on plant features that would suit commercial production and reports of their utilisation by Aborigines, they listed 47 species considered suitable for cultivation in the semi- arid agricultural region of southern Australia.
The 18 species considered to have the best prospects were grouped into three categories:
Most promising species: A. murrayana, A. victoriae
Other promising species: A. jennerae, A. microbotrya, A. pycnantha, A. retinodes, A. rivalis, A. saligna
Lesser-known species: A. anthochaera, A. blakelyi, A. scirpifolia, A. brumalis, A. calamifolia, A. confluens, A. hakeoides, A. hemiteles, A. prainii, A. subrigida.
WATTLE seed REPORT – BY AGTRANS RESEARCH: The Joint Venture Agroforestry Program commissioned Agtrans Research to assess the technical, commercial and economic basis for developing a large-scale wattle seed industry in Australia.