This paper focuses on the adverse effects of soil sodicity and alkalinity on the growth of barley (Hordeum vulgare L.) in a rainfed environment in south-western Australia. These conditions cause the accumulation of salt (called ‘transient salinity’) in the root zone, which decreases the solute potential of the soil solution, particularly at the end of the growing season as the soil dries. We hypothesized that two approaches could help overcome this stress: (a) improved micro-water harvesting at the soil surface, which would help maintain soil hydration, decreasing the salinity of the soil solution, and (b) soil amelioration using small amounts of gypsum, elemental sulfur or gypsum plus elemental sulfur, which would ensure greater salt leaching. In our experiments, improved micro-water harvesting was achieved using a tillage technique consisting of exaggerated mounds between furrows and the covering of these mounds with plastic sheeting. The combination of the mounds and the application of a low rate of gypsum in the furrow (50 kg ha−1) increased yields of barley grain by 70% in 2019 and by 57% in 2020, relative to a control treatment with conventional tillage, no plastic sheeting and no amendment. These increases in yield were related to changes in ion concentrations in the soil and to changes in apparent electrical conductivity measured with the EM38.

Canola monitoring groups were used to gather information so that production across a range of soils, climatic conditions and management strategies could be examined to identify what factors were limiting production. Soil and leaf samples and all inputs were recorded from each paddock monitored. Results showed that it was difficult to draw conclusions when single factors were compared to seed yield, possibly due to the complex interaction that occurs between factors. Factors that appeared to have no linear relationship to seed yield were time of sowing, nitrogen fertiliser applied and plant leaf nitrogen levels. By selecting high yielding and low yielding paddocks possible yield limiting factors could be identified for individual paddocks. INTRODUCTION AND METHOD The area of canola has increased dramatically over the past three years from 10,000 to 75,000 ha, resulting in most growers being new to canola production. To assist in gathering information about canola production, grower groups were formed where growers were encouraged to select one paddock and to monitor all inputs in that paddock. Information recorded was time of sowing, variety, plant population, all inputs (fertiliser, weed control, insect control), rainfall, time of swathing, time of harvest and seed yield and oil content. A soil sample was collected just after sowing in 1999 and leaf samples collected 74 days after sowing in 1998 and 1999. All crops were sown at 5 kg/ha. RESULTS AND DISCUSSION It is widely understood that there are a number of factors limiting yield. Lack of moisture is usually the most limiting with low fertility, poor plant population, poor soil structure, improper crop variety, weeds, insects and diseases all limiting the final possible yield. By undertaking paddock trials each factor can be investigated and a best management strategy developed. This is done by eliminating all other factors and trialing various rates of the factor under investigation. For example if a variety is sown at different times where all the other factors are kept constant (nutrition, weed control, insect control, etc.), then the optimal sowing time for that season can be determined as shown in Table 1. Table 1. Determining optimal sowing date for different varieties 1998 Seed yield at time of sowing (kg/ha) 30 April 21 May 11 June 2 July Pinnacle 3.4* 3.3 2.7 1.7 Clancy 3.3* 3.1 2.2 1.7 Karoo 3.0 3.1* 2.7 1.8 * Optimum sowing time for this season. When the data from the monitoring groups was analysed by selecting each factor and comparing to seed yield, no meaningful relationship could be obtained between that single factor and seed yield. Graph 1 shows the effect of time of sowing on yield. The data shows a random scatter pattern with no significant relationship with yield. The same results occurred with comparisons of total nitrogen fertiliser applied and leaf nitrogen content on seed yield. This scatter of data indicates that there is often no linear relationship between single factors and yield under paddock conditions. This is because the other factors are not eliminated allowing for interaction between the factors which muffles the results and prevents linear comparison of individual factors. This raises the question as to whether monitoring groups data can be useful in understanding what is limiting production? If the data cannot assist growers in improving their production then there is no reason to continue in collecting data in monitoring groups. Variety

Harvest weed seed destruction (HWSD) can be included in an integrated weed management (IWM) program to help control weed populations and combat herbicide resistance. However, it may not be possible or practical to use this technique in every year. This research utilised a computer model, the Weed Seed Wizard, to investigate the impact of employing HWSD every second year. Data from a long term trial in Merredin Western Australia demonstrated the value of residue burning (an early method of HWSD) compared to residue retention on the destruction of Lolium rigidum seed from 2003 to 2013. The agronomic practices utilised in this trial, soil type and rainfall at the field site, and crop yield data were used to parametrise two scenarios in the model. Scenario 1 was based on data from the field trial plots where residue was retained and scenario 2 was based on data from the plots where residue was burnt (i.e. HWSD). A third hypothetical scenario was based on scenario 2, but only incorporated HWSD in every second year. The model gave reasonable predictions of L. rigidum seed production each year (when compared to the actual seed production in the field trial), and accurately predicted when L. rigidum seed numbers would reach very low levels in scenario 2, due to annual HWSD. Scenario 3 indicated that HWSD in every second year could not reduce L rigidum seeds to the same extent as annual HWSD, but the L rigidum population was reduced to and maintained at less than one plant m(-2) at harvest within four years. The model indicated that the total cost of weeds ranged from $85 ha(-1) in scenario 1 to $32 and $27 ha(-1) in scenario 3 and 2. However, income was greatest in scenario 1 as HWSD via burning residue caused a yield reduction in scenario 2 and 3. The results highlight both the benefits of HWSD as a weed management tactic and the value of the Weed Seed Wizard as a tool to investigate different IWM programs.

Land degradation due to compaction is a critical issue facing 21st century agriculture. Deep ripping is a popular solution to remediate compacted Western Australian soils. However, these soils are particularly susceptible to recompaction under vehicle traffic: reliable methods to detect and monitor compaction are therefore needed to inform remediation strategies. Cone penetrometer testing (CPT) is a popular method to detect compaction under vehicle traffic in a range of soil conditions. However, traditional CPT equipment is unsuitable for large-scale use due to its expense and bulk. Dynamic penetrometers circumvent this issue by being inexpensive and man-portable. Such devices have seen recent success in determining properties of soft geotechnical materials but little is known of their performance in ripped soils. This study evaluated the ability of the "PANDA 2" dynamic penetrometer to detect compaction in ripped soils after the passage of aMassey Ferguson four-tonne tractor, which was typical of vehicles used at the test site. Two test sites of contrasting soil types were identified which had previously been ripped and left fallow and untrafficked for several years. Penetration resistance was measured along a high-resolution grid prior to trafficking and after one and five vehicle passes and compared to results from trial pits. Laboratory testing also examined the device's accuracy at shallow depths under controlled conditions. Results showed that the PANDA 2 was able to detect significant changes in penetration resistance after trafficking. However, several limitations on the device's use when interpreting field data were identified. Based on the findings of this study, dynamic penetrometers are not recommended to monitor compaction in ripped soils for the weight of vehicle used here. However, the devices may be of use when examining the passage of heavier vehicles.

SummaryLong‐term research aimed to determine whether narrow row spacing and harvest weed seed destruction, in combination with herbicide use, would be sufficient to drive a Lolium rigidum population to extinction. A trial was run from 1987 to 2013, with treatments including crop row spacings of 9, 18, 27 or 36 cm and crop residue burning or retention. Herbicides were applied to reflect regional practices. The initial trial design was randomised, but treatments were maintained in each plot over the following years. Lolium rigidum seed production at harvest was assessed from 2003 to 2013. Average crop yield was higher in the unburnt plots (1638 kg ha−1) than the burnt plots (1530 kg ha−1) and greater at narrow row spacing, with an average yield of 1658, 1637, 1548 and 1492 kg ha−1 in the 9‐, 18‐, 27‐ and 36‐cm spacings. Lolium rigidum seed at harvest was reduced in the burnt plots (57 seeds m−2) compared with the unburnt plots (297 seeds m−2) and was reduced at narrow row spacing, with an average of 58, 78, 223 and 333 seeds m−2 in the 9‐, 18‐, 27‐ and 36‐cm row spacings. By 2013, L. rigidum seed production was reduced to an average of 0 seeds m−2 in the narrow row spacing, burnt plots.

A long term trial (2003 to 2013) investigated annual ryegrass seed production in a crop rotation in Merredin, WA. The weed control methods in the trial included herbicides, or herbicides combined with weed seed destruction at harvest. Data from this trial was used to investigate varying scenarios of harvest weed seed destruction using the Weed Seed Wizard (WSW) model. The WSW demonstrated that herbicides plus weed seed destruction at harvest could reduce the annual ryegrass seedbank to very low levels over eight years. Use of herbicides alone did not reduce the seedbank to the same extent over the entire 11 year span of the trial. Harvest weed seed destruction in alternate years reduced the annual ryegrass seedbank to very low levels compared to use of herbicides alone.

1. Several options exist to ameliorate subsoil acidity with incorporated lime. The method chosen will depend on pH profile, yield potential, budget, area affected, soil type and occurrence of other constraints that may be impacted. 2. Modified deep ripping techniques can incorporate more topsoil and surface applied lime while at the same time effectively removing subsoil compaction. 3. Applying adequate lime to ameliorate the soil pH profile to depth is of utmost importance and the rate of lime applied should not be compromised to pay for incorporation, although lime applications can be split with some applied before and some a year or two after incorporation.

PRE herbicides are generally less effective in conservation farming systems because of high levels of crop residue. However, performance can be improved if the herbicides are applied with a high carrier volume. This research investigated the interaction of carrier volume and row spacing or height of crop residue on the control of rigid ryegrass with trifluralin, at Cunderdin and Wongan Hills Western Australia. To create plots with varying residue row spacing in 2011, wheat was seeded in 2010 using a narrow row spacing (25 or 22 cm at Cunderdin and Wongan Hills), wide spacing (50 or 44 cm), or not planted to wheat. Narrow or wide row spacing or no crop plots had an average residue biomass of 4480, 3560, and 2430 kg ha−1at Cunderdin and 1690, 1910, and 1030 kg ha−1at Wongan Hills. To vary residue height, the wheat was harvested to produce tall, medium, or short crop residue (22, 13, and 5 cm at Cunderdin and 27, 22, and 17 cm at Wongan Hills). Rigid ryegrass seeds were broadcast onto each site in 2011 and trifluralin was sprayed using 50, 75, or 100 L ha−1carrier volume (directly prior to seeding). Increased carrier volume increased spray coverage at both sites (average cover of 9, 15, and 26% at 50, 75, and 100 L ha−1), leading to improved control of rigid ryegrass (68, 75, and 82% control at Cunderdin and 23, 41, and 68% control at Wongan Hills). Reduced crop residue height or increased row spacing led to reduced rigid ryegrass density at Cunderdin but had no impact at Wongan Hills. Therefore, carrier volume has a more consistent impact on the performance of trifluralin than crop residue row spacing or height.

Pre-emergent herbicides are generally less effective in no tillage farming systems due to high levels of crop residue. However, performance can be improved if the herbicides are applied with a high carrier volume. This research investigated the interaction of carrier volume and height or spacing of crop residue on the control of annual ryegrass with trifluralin. To create plots with varying crop residue characteristics in 2011, wheat was sown in 2010 using a narrow row spacing, wide spacing or left bare (i.e. not sown to wheat), at Wongan Hills and Cunderdin, Western Australia (WA). The wheat was harvested to produce tall, medium or short crop residue. Annual ryegrass seeds were broadcast onto each site in 2011 and trifluralin was sprayed using 50, 75 or 100 L ha−1 carrier volume (directly prior to sowing). Increased carrier volume increased spray coverage at both sites (average cover of 9.0%, 15.0% and 25.5%), leading to improved control of annual ryegrass (average density of 24, 19 and 11 plants m−2). However, altered row spacing or harvest height in 2010 (i.e. altered crop residue characteristics) did not consistently affect spray coverage. Reduced crop residue height or increased row spacing improved annual ryegrass control at Cunderdin but had no impact at Wongan Hills. It is clear that carrier volume has a more consistent impact on the performance of trifluralin than crop residue (in WA where the biomass of crop residues is relatively low). These results are encouraging as it is usually easier for growers to increase carrier volume than to adjust crop residues, for improved annual ryegrass control in no tillage systems.

Field trials were conducted to study the emission of nitrous oxide during the summers of 2012 and 2013 from fields with harvested field pea, harvested wheat and winter fallow at Merredin and Cunderdin respectively, two wheat growing regions of Western Australia. The nitrous oxide emission fluxes from these treatments were regularly monitored during the postharvest summer period using a closed chamber technique, before and after wetting the soil. Very low nitrous oxide flux occurred in the dry soil conditions prior to wetting. However, significantly increased nitrous oxide flux was observed at both the sites after wetting, with emissions from a harvested field pea plots being 55-86 fold higher than prior to wetting at the two sites. After wetting, the field pea plots also had significantly higher emissions (3.47-3.87 g N2O-N ha(-1) h(-1)) than those following winter fallow (1.17-1.95 g N2O-N ha(-1) h(-1)), although no nitrogen fertiliser was applied to either during the crop growing period. The harvested wheat plots had emissions that were similar (1.18-3.15 g N2O-N ha(-1) h(-1)) or higher than the winter fallow treatment. The sudden increase in nitrous oxide was observed 3 h after wetting, with a significant reduction in nitrous oxide flux occurring approximately 20 h after wetting. This indicates the need for regular monitoring of nitrous oxide flux to capture the emission pulses that occur under favourable conditions. Nitrous oxide flux was positively correlated with soil nitrate-N, water filled pore space and soil temperature at both the sites. The study shows that the use of winter fallow does not result in high soil nitrous oxide emissions over the following summer, compared with harvested wheat or field peas. The studies are important because more frequent summer rains are predicted in the region, and as shown in this study, high summer temperature together with rainfall could lead to nitrous oxide emission peaks. (C) 2014 Elsevier B.V. All rights reserved.

PRE herbicides are less effective in the zero-tillage system because of increased residual crop stubble and reduced soil incorporation. However, since weeds are not physically controlled in the zero-tillage system, reliance on efficacy of PRE herbicides is increased. This research investigated the impact of carrier volume and droplet size on the performance of PRE herbicides (in wheat crops at four sites in 2010) to improve herbicide efficacy in conditions of high stubble biomass in zero-tillage systems. Increasing carrier volume from 30 to 150 L ha−1increased spray coverage on water-sensitive paper from an average of 5 to 32%. Average control of rigid ryegrass by trifluralin (at Cunderdin and Merredin sites) and trifluralin or pyroxasulfone (at Wickepin and Esperance sites) improved from 53 to 78% with increasing carrier volume. Use of ASABE Medium droplet size improved spray coverage compared with ASABE Extremely Coarse droplet size, but did not affect herbicide performance. It is clear that increased carrier volume improves rigid ryegrass weed control for nonwater-soluble (trifluralin) and water-soluble (pyroxasulfone) PRE herbicides. Western Australian growers often use low carrier volumes to reduce time of spray application or because sufficient high-quality water is not available, but the advantages of improved weed control justifies the use of a high carrier volume in areas of high weed density.

Two field studies were conducted at Mt Barker in 2010 and 2011 to investigate techniques to reduce annual ryegrass seed set. Both experiments included swathing with a commercially available sprayer kit attached and desiccation of the standing crop. Results in 2010 showed, on average, desiccation with diquat reduced the viable ryegrass seed production by 65% and, on average, desiccation or spraying on the swather with glyphosate reduced the viable ryegrass seed production by 45% while spraying paraquat on the swather reduced the viable ryegrass seed production by 80%. The 2011 results showed swathing with above 2.4 L/ha of glyphosate at either 30% or 60% seed colour change of the canola reduced ryegrass seed viability by an average of 43% compared to the average of the nil and swathing alone while desiccation with above 2.4 L/ha of glyphosate at either 30% or 60% seed colour change of the canola reduced ryegrass seed viability by an average of 73% compared to the average of the nil and swathing alone. Spraying on the swather with paraquat reduced the viable ryegrass seed production by 69%.

Adoption and development of Controlled Traffic Farming (CTF) systems for dryland cropping in WA have been challenged recently by:- - More unprofitable growing seasons for most growers since the turn of the century, compared to the 90s. Thus a reduced capacity to invest in the machinery changes to CTF. - Increased frequency of dry autumns encouraging sowing dry sowing to complete large cropping programs before the latest advisable date. Thus an urgency to sow as much area as possible per day while suitable sowing conditions have developed and encouraging the use of wider seeders which may not easily fit a CTF system (>about 12m). - Use of increasingly powerful and larger mass tractors and increasing large capacity air carts and chaser bins to allow better efficiency of operations during appropriate sowing windows, but larger risk of subsoil damage. - Rapid adoption of deep tillage methods relatively new to the WA wheatbelt; Spading and inversion mouldboard ploughing. Very few of these growers are using CTF despite the capacity of such deep cultivated soils to recompact easily. New field data was collected of wheat yield and grain quality after normal traffic on deep ripped yellow sand. This is used to estimate the grain yield and income benefits from CTF after deep ripping and calculate the estimated payback period of conversion to CTF. Analysis of factors other than seeder width to improve seeding capacity is made to help growers consider increased seeding speed and reduced reloading frequency as alternatives to increase seeding capacity. Data from deep compaction by very heavy vehicles is also used to alert the industry to future risks of very high axle loads.

Conventional soil ripping has high fuel consumption because it involves high draft force and may produce large soil clods. This experiment compares the use of shallow leading tines ahead of the main tine with use of a conventional single-tine ripper. The study showed that attaching a single, shallow leading tine ahead of, and in line with, the main tine and 25-40% shallower in depth gave the greatest significant decrease in specific draft force. This led to a fuel reduction from 13.6 to 11.5L/ha, or a saving of 15% when ripping a moist loamy sand soil to 330mm depth. Attaching more than one shallow lead tine ahead of the ripper did not significantly affect specific draft forces, whether the shallow lead tines were in line or offset. Other advantages of using the shallow leading tine ripper over the conventional ripper are: improved soil tilth by significantly decreasing soil clod size; potentially a wider moisture range for ripping the soil (as soil clods are smaller and drier soil increases clod size) thus increasing the time available for the operation; and decreased depreciation of ripping components.

Summary1.It has been established that the timing of abscission has a major impact on the dispersal distances achieved by individual seeds, and yet there is little information available on seed release thresholds.2.The current research usedConyza bonariensisto examine seed release thresholds of seed heads at varying ages and at varying orientations (in relation to the direction of the air flow).3.Wind speeds of 0–70 m s−1were used to remove the seeds from seed heads harvested directly prior to exposure to wind. Seed head age at the time of harvest from the plant (0–10 days old, where day 0 is the day on which the seed head opens) and seed head orientation (in relation to the direction of air) were altered.4.While seed loss increased with increasing wind speed, average loss from seed heads increased from 49·4% on the day they opened to 92·8% from seed heads open for 10 days. Further, there was an average seed loss of 76·4%, 72·5%, 73·9%, 65·3% and 58·8% for wind orientations of 0, 45, 90, 135 and 180°, where 0° indicates wind directed up towards the base of the hemispherical seed head (simulating an updraft), 90° indicate wind directed towards the side of the seed head (horizontal wind) and 180° indicate wind directed down towards the top of the seed head (simulating a downdraft).5.Seeds were released in the strongest wind events and were more likely to be released in updrafts or horizontal winds rather than downdrafts. Both of these factors interact with seed aging in a way that will increase the potential dispersal distance. Given that minor changes to abscission can have major impacts on maximum dispersal distance; these factors need to be taken into account when formulating models on dispersal.6.This research supports the theory that where greater dispersal confers an evolutionary advantage, wind‐dispersed plants would be likely to evolve strategies to ensure maximum dispersal capability.

Cultivation between crop rows is a common tool for weed suppression in Europe and in row-crops in eastern Australia, which is not commonly practised in Western Australia. The degree of damage this technique can cause the weeds is influenced by weed species, soil engaging tool type and ground speed, soil moisture levels and the probability of post-cultivation rain. The damage to the lupin crop will also be influenced by speed of cultivation, degree of soil throw, stage of crop development and crop density. In-crop harrowing is being used in Europe to remove weeds in organic cereal crops but this technique does not handle stubble. Chain type or rotary harrows can handle stubble and can be adjusted for aggressiveness by changing the chain angle. Treatments included inter-row cultivating at 3 stages of wild radish in a lupin crop, inter-row cultivating again 4 weeks later and Phoenix rotary harrowing at 3 stages of wild radish. No treatment was very effective at reducing wild radish seed set as the in-row wild radish produced high seed numbers. A range of pre-emergent grass herbicides or other techniques need to be tested in the future to reduce in-row weeds.