John Bartle

Scale of biomass production from new woody crops for salinity control in dryland agriculture in Australia

There is scope internationally to utilise surplus and degraded agricultural land for biomass crops that might also be environmentally beneficial. For example, dryland salinity in southern Australian could be ameliorated using profitable woody biomass crops. A model was developed to predict biomass production from such woody crops. At a biomass price of A

Sapling and coppice biomass production by alley-farmed ‘oil mallee’ Eucalyptus species in the Western Australian wheatbelt

35/t (green) and a water use efficiency of 1.8 dry g/kg of water, profitable woody crops could produce 39 million t/year of dry biomass from 1.5% of farmland in the 300-400mm rainfall zone, and 8% of farmland in the 401–600 mm rainfall zone of the southern Australian wheatbelt.

Enhancing tree belt productivity through capture of short-slope runoff water.

Summary Nine promising taxa of ‘oil mallees’ were planted in twin row alley culture at twelve sites across the Western Australian wheatbelt. Two harvest regimes were imposed (i) 2.5-year-old saplings cut to ground level in summer and their coppice shoot biomass harvested twelve months later, and (ii) 3-year-old saplings cut in winter and coppice shoots harvested twelve months later. The eight northwestern sites were generally more favourable and mostly comprised acidic subsoils with deep non-saline groundwater, while the four southeastern sites had alkaline and saline subsoils and shallow, saline groundwater. Species native to the northern wheatbelt (Eucalyptus horistes, E. kochii subsp. kochii and E. kochii subsp. pienissima) performed strongly in northern sites but grew and survived poorly in the south. E. vegrandis and E. angustissima grew well initially but survived and regenerated unsatisfactorily after first cutting at most sites. E. polybractea (a species from New South Wales and Victoria), and the central Western Australian wheatbelt species, E. gratiae and E. loxophleba subsp. lissophloia, (smooth barked York gums) performed well as saplings and in coppice format at virtually all sites. Biomass production of saplings at first cut was strongly correlated with water availability as assessed by rainfall, topsoil depth and pan evaporation. Survival of coppicing trees was sensitive to harsh conditions such as presence of shallow, saline groundwater and cold winter conditions during early regeneration. Coppice productivity of all species was strongly correlated with sapling size at first cutting. The study suggests that optimal management regimes in terms of age and size at first cut, and frequency of subsequent harvests, will be strongly determined by species and site conditions, with late spring/early summer harvests being most favourable for survival and coppice vigour.

Budgets of water use by Eucalyptus kochii tree belts in the semi-arid wheatbelt of Western Australia

A selection of multi‐stemmed, drought‐tolerant mallee eucalypts, planted in belt form and integrated with crops in dryland agricultural areas of Australia, may be able to produce biomass as a commercially attractive feedstock for biofuel production. This study aimed to determine if small (40–50 cm high) bunds along mallee belts could trap otherwise underutilized surface water runoff within paddocks, thereby increasing water available to the mallee trees and their growth rates. An experiment was established in 5 year‐old Eucalyptus polybractea (RT Baker) mallee belts near the town of Narrogin in the central wheatbelt area of Western Australia. Bunds led to significant (12%) increases in biomass accumulation after about 2 years and 35% increases at around 3 years. Bunds also led to significant increases in predawn leaf water potential and significant decreases in soil water deficit within 12 months, which persisted for the remainder of the 39 month trial. We suggest that the increase in biomass accumulation was largely due to increased water availability, but that increased nutrient supply from run‐on and trapping of organic residues may have also had some effect on bunded plots, despite our attempts to mitigate this effect by experimentally adding nutrients to all treatments. Results show that installing bunds along mallee belts would be a cost‐effective investment at sites where within‐paddock runoff is likely (i.e. gently sloping and with a loamy sand or heavier soil texture). Installation costs should be offset by improved biomass production within a few years and ongoing improvements in growth over the long term.