Managing water-repellent soils

A study of water-repellent soils has led to some management recommendations

Soil acidity on high rainfall pastures

Most soils of the high rainfall area of south-western Western Australia are naturally acis. The most acid group of soils, the peaty sands. have been routinely limed before subterranean clover pastures were established since research in the 1950s showed that poor Rhizobium nodulation could be overcome with the application of about 2 tonnes per hectare of coastal limesand

Soil acidity - high rainfall pastures

A. Lime on old land pastures. 80BU13, 80BU14, 80BU15, 80BU16, 80BU17, 80BY7, 80BY16, 81AL10, 81AL11, 8IAL12, 81AL13, 81AL14, 81AL15, 81AL16, 81BU18, 81BY15, 81BY16, 81BY17, 81BY18, 81BY19, 81BY24, 81BY25, 81BY16, 81MA12, 81W9, 81Wl0, 81Wll, 82AL2, 82AL3, 82AL4, 82ALS, 82AL6, 82ALSS, 82BU6, 82BU7, 82BU8, 82BY37, 82HA35, 82HA36, 82HA38, 82MA20, 82PE1, 83AL7, 83AL8, 83AL9, 83AL10, 83AL11, 83AL12, 83AL13, 83AL14, 83BU20, 83BU24, 83BU25, 83BU26, 83BY29, 83HA19, 83HA40, 83HA41. B. Lime on new land pastures 82AL7, 82AL8

Visualisation and optimisation of shielding gas coverage during gas metal arc welding

The density gradients and flow characteristics of the gas shield during gas metal arc welding (GMAW) of DH36, higher strength ‘construction steel’ were visualised using schlieren imaging. A systematic study was undertaken to determine the effect of shielding gas flow rate, as well as changes in the nozzle stand-off and angle, on the weld quality. The schlieren images were used to validate 2D and 3D magnetohydrodynamic (MHD) finite element models of the interaction between the Ar shielding gas, the arc and the ambient atmosphere. Weld porosity levels were determined through x-ray radiography. Sufficient shielding gas coverage was provided at a minimum of 9 l/min pure Ar, irrespective of relatively large increases in the nozzle stand-off and angle. Using 80% Ar/20% CO2 shielding gas, and 86% Ar/12% CO2/2% O2 shielding gas with flux cored arc welding (FCAW-G), achieved good quality welds down to 5 l/min. The introduction of 12 l/min in production welding has been implemented with no compromise in the weld quality and further reductions are feasible

Solid Solid Phase Transitions and tert-Butyl and Methyl Group Rotation in an Organic Solid: X-ray Diffractometry, Differential Scanning Calorimetry, and Solid-State H-1 Nuclear Spin Relaxation

Using solid state 1H nuclear magnetic resonance (NMR) spin-lattice relaxation experiments, we have investigated the effects of several solid-solid phase transitions on t-butyl group and methyl group rotation in solid 1,3,5-tri-t-butylbenzene. The goal is to relate the dynamics of the t-butyl groups and their constituent methyl groups to properties of the solid determined using single-crystal X-ray diffraction and differential scanning calorimetry (DSC). On cooling, the DSC experiments see a first-order, solid-solid phase transition at either 268 K or 155 K (but not both) depending on thermal history. The 155 K transition (on cooling) is identified by single-crystal X-ray diffraction to be one from a monoclinic phase (above 155 K) where the t-butyl groups are disordered (that is, with a rotational six-fold intermolecular potential dominating) to a triclinic phase (below 155 K) where the t-butyl groups are ordered (that is, with a rotational threefold intermolecular potential dominating). This transition shows very different DSC scans when both a 5 mg polycrystalline sample and a 19 mg powder sample are used. The 1H spin-lattice relaxation experiments with a much larger 0.7 g sample are very complicated and, depending on thermal history, can show hysteresis effects over many hours and over very large temperature ranges. In the high-temperature monoclinic phase, the t-butyl groups rotate with NMR activation energies (closely related to rotational barriers) in the 17-23 kJ mol-1 range and the constituent methyl groups rotate with NMR activation energies in the 7-12 kJ mol-1 range. In the lowtemperature triclinic phase, the rotations of the t-butyl groups and their methyl group in the aromatic plane are quenched (on the NMR time scale). The two out-of-plane methyl groups in the t-butyl groups are rotating with activation energies in the 5-11 kJ mol-1 range