Phase Farming with Trees: A report for the RIRDC/LWRRDC/FWPRDC Joint Venture Agroforestry Program

A scoping study was undertaken to determine the economic and biophysical feasibility of a proposal to research a system of phase farming with trees (PFT) in medium to low (300-600 mm) rainfall areas of southern Australia. This system is designed to use trees grown in very short term rotations (3-5 years) to rapidly de-water farming catchments, at risk of salinity, by depleting unsaturated stored soil water and reducing recharge while producing utilizable products. If feasible, the system will utilize a resource that is currently contributing to environmental problems while building more sustainable agricultural systems. Potential benefits include decreased salinization, improved farm cash flows, improved soil structure and acting as a disease and weed break..

Observation of hard scattering in photoproduction events with a large rapidity gap at HERA

Events with a large rapidity gap and total transverse energy greater than 5 GeV have been observed in quasi-real photoproduction at HERA with the ZEUS detector. The distribution of these events as a function of the $\gamma p$ centre of mass energy is consistent with diffractive scattering. For total transverse energies above 12 GeV, the hadronic final states show predominantly a two-jet structure with each jet having a transverse energy greater than 4 GeV. For the two-jet events, little energy flow is found outside the jets. This observation is consistent with the hard scattering of a quasi-real photon with a colourless object in the proton.Comment: 19 pages, latex, 4 figures appended as uuencoded fil

Phase farming with trees: a new weapon in the fight against dryland salinity?

A system to overcome dry land salinization of farming systems in medium to low (300-600 mm) rainfall areas of southern Australia is proposed. Phase farming with trees (PFT) is designed to use trees grown in very short term rotations (3-5 years) to rapidly de-water farming catchments at risk of salinity, by depleting soil water while producing utilizable products such as wood fibre and biomass. The tree phase is followed by an agricultural phase of a length defined by the persistence of the hydrological buffer created by the trees. The system thus utilizes a resource (groundwater recharge) that is contributing to environmental problems while building more sustainable agricultural systems. Potential benefits include decreased salinization, improved soil structure and acting as a disease and weed break. Production of large amounts of biomass suitable for "green" electricity will decrease Australia's emissions of Greenhouse gases. The biophysical feasibility of PFT was assessed for several sites in the 300-600 mm rainfall zone of southern Australia using the WAVES model. Several scenarios were examined, with these suggesting broad differences in likely response to the PFT system. The modelling suggests that the premise of the PFT system (viz. depletion of sub-soil moisture reserves under trees and subsequent recharge under agriculture) is realistic. Moreover, the outputs suggest different tree planting strategies according to soil and hydrological conditions

Catchment scale evaluation of trees, water and salt

Rising ground-waters and resultant salinity threaten agricultural land, conservation reserves and water resources in southern Australia. Although revegetation with woody plants is often considered as a strategy to restore catchment water balances, farm forestry has not been adopted in low-rainfall environments to the extent of that in high rainfall zones. Similarly, there is some conjecture that the proportion of revegetation needed to restore catchment water balances may be as high as 80%. The JVAP publication Trees, Water and Salt provides a set of guidelines for revegetation of farmland, however these have not been tested at the catchment scale in drier (<400 mm annual rainfall) environments that are representative of the wheat and wool-belt of much of southern Australia. Reforestation in these regions is often of limited scale, and thus at an inappropriate scale to assess catchment scale responses. This study measured the hydrologic response of an 80 ha catchment to partial reforestation, near Wickepin, Western Australia. This region, which has around 300 mm annual rainfall, has agriculture that comprises rotations of cropping and pastures. These trees were established using the procedures outlined in Trees, Water and Salt. An issue with dryland reforestation has been the lack of clear economic drivers. The emergence of markets for carbon sequestration and bioenergy from trees, in response to national climate change policies may increase the future rate of reforestation. Key issues include understanding the rates of both sequestration and biomass production in drier environments such as Wickepin and also how best to integrate reforestation with agricultural production. Of particular interest are the interaction of belts of trees with agriculture and the utilization of land that is poorly productive, such as that which has been affected by salinity