Search

Herbicides are used extensively in Australian grain cropping systems. Despite occasional observations of herbicide-induced phytotoxicity, there is little information on the persistence and carryover of multiple herbicide classes in cropping soils and the risk to subsequent crops. Two soil surveys were conducted in 2015 (n = 40) and 2016 (n = 42) across different Australian grain cropping fields prior to sowing of winter crops, and soil samples analysed for herbicide residues (16 analytes in 2015 and 22 analytes in 2016). Samples in 2015 were taken at two depth (0–10 cm and 10-30 cm), whilst samples in 2016 were taken in topsoil (0–10 cm) only, but from two discrete locations in each field. Our research in both years found at least one herbicide (or herbicide metabolite) residue at all sites, with a median of 6 analytes detected in 2015 and 7 analytes detected in 2016. The most frequently detected residues were glyphosate and its primary breakdown product aminomethylphosphonic acid (AMPA), in 87 and 100%, respectively, of topsoil (0–10 cm) samples in 2015, and 67 and 93% of samples in 2016. The median concentration of glyphosate in 2015 was 0.12 mg kg−1, while AMPA was 0.41 mg kg−1. In 2016, median concentrations of glyphosate and AMPA were 0.22 mg kg−1 and 0.31 mg kg−1. Residues of 2,4-dichlorophenoxyacetic acid, trifluralin and diflufenican were also detected in >40% of topsoil samples in both seasons, but with median concentrations of <0.05 mg kg−1. A literature review found limited availability of phytotoxicity thresholds for major grain crops exposed to soilborne herbicide residues. A risk assessment using available thresholds suggested that although up to 29% of fields contained trifluralin residues that could constrain cereal crop growth, and 24% of fields contained residues of phenoxy or sulfonylureas that could affect dicotyledonous crops, the majority of these fields when planted with tolerant crops would be unlikely to be affected by herbicide residues. Mo

Purpose Soil water repellence causes uneven soil wetting which can constrain dryland crop and pasture establishment and yield. The same processes are likely to affect nutrient availability from soil and fertiliser, but the effects of repellence on crop growth and nutrition per se have seldom been reported. Here, we investigated early wheat (Triticum aestivum cv. Mace) growth and nutrient uptake responses to repellence. Methods Wheat was furrow-sown in severely repellent sandy loam soil (with a wettable furrow base to allow for germination) or completely wettable soil, under uniform plant density and variable topsoil thickness (20 or 100 mm) and fertiliser band placement (below or away from the seed). Tiller number, shoot dry matter, shoot N concentration, total nutrient uptake, and root length density (RLD) were determined. Results Contrary to expectations, repellence significantly increased tiller number (by up to 2 tillers per plant), shoot dry matter (by 82%), shoot N concentration (by 0.3% N), and total nutrient uptake (by 87%) at 51 days after sowing, regardless of topsoil thickness and fertiliser placement. In the furrow, RLD of repellent treatments was also nearly double that in wettable treatments when fertiliser was banded below the seed. Results suggest that preferential soil wetting of the furrow in repellent treatments favoured plant nutrient uptake under regular but low water supply. Conclusion We conclude that for water-repellent soils with limited water supply, water harvesting techniques such as furrow sowing and banding wetting agents could boost water and nutrient uptake and early crop growth.

Negative potassium (K) balances on farmlands globally are widespread because fertiliser K input is often less than losses (leaching) and removal of K in hay, straw and grain, which leads to a rundown of plant-available K. When soil K reserves are not large and the plant-available K pools are not well buffered, the risk of K rundown in soils is high. In the south-west of Western Australia, soil K rundown, particularly by continuous cropping or in systems where a large portion of crop biomass is removed, is increasing the prevalence of crop K deficiency even on soils where K was not previously a limiting factor for crop yields. While fertiliser K is required for adequate supply of plant-available K, maximising K use efficiency is also important for cropping profitability and sustainability in dryland agriculture. Plant K uptake and use efficiency can be affected by soil types, crop species and sequences, seasonal conditions, and K management. In water-limited environments, crop K nutrition, especially root access to subsoil K, plays a crucial role in promoting root growth, regulating plant water relations and alleviating biotic and abiotic stresses. Optimised use of both soil and fertiliser K is increasingly necessary to sustain crop yields under stressed conditions in the context of K rundown in soils.

A controlled-environment study was conducted to explore possible synergistic interactions between the feremycorrhizal (FM) fungus Austroboletus occidentalis and soil free-living N2-fixing bacteria (diazotrophs). Wheat (Triticum aestivum) plants were grown under N deficiency conditions in a field soil without adding microbial inoculum (control: only containing soil indigenous microbes), or inoculated with a consortium containing four free-living diazotroph isolates (diazotrophs treatment), A. occidentalis inoculum (FM treatment), or both diazotrophs and A. occidentalis inoculums (dual treatment). After 7 weeks of growth, significantly greater shoot biomass was observed in plants inoculated with diazotrophs (by 25%), A. occidentalis (by 101%), and combined inoculums (by 106%), compared to the non-inoculated control treatment. All inoculated plants also had higher shoot nutrient contents (including N, P, K, Mg, Zn, Cu, and Mn) than the control treatment. Compared to the control and diazotrophs treatments, significantly greater shoot N content was observed in the FM treatment (i.e., synergism between the FM fungus and soil indigenous diazotrophs). Dually inoculated plants had the highest content of nutrients in shoots (e.g., N, P, K, S, Mg, Zn, Cu, and Mn) and soil total N (13–24% higher than the other treatments), i.e., synergism between the FM fungus and added diazotrophs. Root colonization by soil indigenous arbuscular mycorrhizal fungi declined in all inoculated plants compared to control. Non-metric multidimensional scaling (NMDS) analysis of the bacterial 16S rRNA gene amplicons revealed that the FM fungus modified the soil microbiome. Our in vitro study indicated that A. occidentalis could not grow on substrates containing lignocellulosic materials or sucrose, but grew on media supplemented with hexoses such as glucose and fructose, indicating that the FM fungus has limited saprotrophic capacity similar to ectomycorrhizal fungi. The results revealed synergistic i

Purpose: Soil water repellence causes uneven soil wetting which can constrain dryland crop and pasture establishment and yield. The same processes are likely to affect nutrient availability from soil and fertiliser, but the effects of repellence on crop growth and nutrition per se have seldom been reported. Here, we investigated early wheat (Triticum aestivum cv. Mace) growth and nutrient uptake responses to repellence. Methods: Wheat was furrow-sown in severely repellent sandy loam soil (with a wettable furrow base to allow for germination) or completely wettable soil, under uniform plant density and variable topsoil thickness (20 or 100 mm) and fertiliser band placement (below or away from the seed). Tiller number, shoot dry matter, shoot N concentration, total nutrient uptake, and root length density (RLD) were determined. Results: Contrary to expectations, repellence significantly increased tiller number (by up to 2 tillers per plant), shoot dry matter (by 82%), shoot N concentration (by 0.3% N), and total nutrient uptake (by 87%) at 51 days after sowing, regardless of topsoil thickness and fertiliser placement. In the furrow, RLD of repellent treatments was also nearly double that in wettable treatments when fertiliser was banded below the seed. Results suggest that preferential soil wetting of the furrow in repellent treatments favoured plant nutrient uptake under regular but low water supply. Conclusion: We conclude that for water-repellent soils with limited water supply, water harvesting techniques such as furrow sowing and banding wetting agents could boost water and nutrient uptake and early crop growth.

We propose an image-based technique to measure the volume, weight and the size distribution of gravel particles in a gravel-soil mixture. The proposed method uses 3D scanning and a surface reconstruction algorithm to generate a high-resolution depth image, which is then used to accurately estimate the volume and weight of each gravel particle. The proposed method is evaluated on several gravel soil samples collected from 25 farming locations. The experimental results show that the proposed technique produces an accurate estimate of gravel volumes and gravel weights. It achieves a relative root mean square error of 4% for large gravel particles and an overall correlation of 0.99 with the ground truth, for the task of gravel volume estimation. For the estimation of gravel weight distribution, the proposed method can reach a low root mean square error of 0.54%. The rapid measurement of the full spectrum of coarse fragments in soil, using this method, is an advantage compared to the manual methods.

Agricultural research in broadacre farming in Western Australiahas a strong history, resulting in a significant public resource of knowledge about biophysical processes affecting crop performance. However, translation of this knowledge into improved on-farm decision making remains a challenge to the industry.Online and mobile decision support tools to assist tactical farm management decisions are not widely adopted, for reasons including: (1) they take too much time and training to learn; and (2) they aren’t integrated with the data they need or with each other, making their use too time-consuming. Meanwhile, as farmers accumulate more data from their machinery, they find themselves unable to use that data to inform decision making.In an ideal future, variable rate technology (VRT) could be programmed to apply optimal rates of fertilisers. However, the existing suite of models and tools are derived from small-scale controlled field experiments and are not suitable forfine-scale paddock management. Using 14 years of data from a farm in the eastern wheatbelt of Western Australia, we investigate the calibration and extension of an agro-economic modelfor spatial prediction of the effects of nitrogen applicationson wheat yield and gross return.We use a simple response curve model, NP-Decide,that was developed in Western Australiaand remains in common use.

The measurement of bulk density in gravelly soils (>15% soil particles >2 mm) is more time‐consuming than for other soils. The excavation method, usually employed for measurement of bulk density in gravelly soils, includes excavating a void and calculating volume of the void from the weight and density of the material (e.g. sand and plaster cast) used to fill the void. A 3‐dimensional (3D) scanning system was developed to measure the volume of the void created when using the excavation method. The 3D scanning system combined a time‐of‐flight camera (Kinect ™), the KinectFusion algorithm, MeshLab and a portable computer to produce a 3D model of the void or plaster cast. Experiments were completed at three field sites where soil gravel (>2 mm) content ranged from 35 to 71% to assess the performance of the system. The void volume measured using the 3D scanning system was highly correlated with measurements using the plaster cast method (r = 0.99). The cumulative time taken to measure soil bulk density using 3D scanning was significantly (P < 0.001) less than for the sand replacement at 0–10, 10–20, 20–30 and 30–40 cm depth. The faster measurement of subsurface bulk density is a significant advantage of the 3D scanning system; the time taken to measure bulk density to 40 cm in 10 cm increments using the 3D scanning system was about one‐third of the sand method.

This study assessed whether more potassium (K) was required for optimal growth and grain yield of cereal crops under drought and salinity than under non-stressed conditions. In 2011, three experiments on wheat (Triticum aestivum L.) with four K rates (0, 20, 40, 80kg K/ha), four application times (0, 5, 10, 15 weeks after sowing, WAS) and two sources (KCl, K2SO4) were conducted in the central and southern grainbelts of Western Australia. The lack of plant response to K supply at the sites of Bolgart (36mg K/kg at 0-30cm) and Borden (25mg K/kg at 0-30cm), compared with significant gain in K uptake, dry matter and grain yield at Dowerin (29mg K/kg at 0-30cm), was not explained by differences in soil K levels. However, rain fell regularly through the growing season at Bolgart and Borden, whereas a dry spell occurred from stem elongation to grain development at Dowerin. The effectiveness of K application time followed the trend of 0, 5>10>15 WAS. In 2012, barley (Hordeum vulgare L.) was grown on a moderately saline (saturation extract electrical conductivity ∼4dS/m) and low K (20mg K/kg) farm in the central grainbelt and treated with 0, 20, 40 and 120kg K/ha. Applying K increased K uptake but decreased Na uptake, especially at 120kg K/ha. Plant growth and grain yield increased with K supply, but the difference between the K rates was relatively small, indicating possible partial K substitution by Na. Higher than normal fertiliser K supply on low K soils would enhance the adaptation by cereals to water-limited environments, but K-fertiliser management on moderately saline soils may need to account for both K and Na uptake and use by the crops.

Aims: There is still limited information about the dynamics of potassium (K) uptake and use over the growth cycle in cereals, but quantification of such relationships is necessary to model crop response to K and improve K fertiliser practice. This study examined the effects of varying K supply on K use efficiency, leaf gas exchange, root and shoot growth at successive stages of plant phenological development, and on seed yield in wheat (Triticum aestivum L.). Methods: The study was conducted with a low-K loamy sand in a naturally-lit glasshouse. Six rates of soil K were applied as 15, 22.5, 30, 45, 75, 135 mg K kg-1, and six harvests were made to assess growth responses at different stages. Results: Tiller development, shoot dry weight, leaf photosynthesis and transpiration efficiency were closely related to soil K supply with time. Plants with 15 to 45 mg K kg-1 had lower root-to-shoot ratio than those supplied with 75 or 135 mg K kg-1. Plants showed maximal K accumulation in shoots prior to anthesis regardless of K rates, but K use efficiency differed during growth among the treatments. Adequate K supply enhanced seed yield by increasing ear numbers, single seed weight and harvest index. Conclusions: The rates of K supply affect K use efficiency, the root-to-shoot ratio and seed yield in wheat with a key feature of growth on a low-K sand as active K uptake during vegetative growth and subsequent reliance on K redistribution for reproductive growth. The poor adaptation of root growth to K deficiency may impair the plant's ability for nutrient acquisition especially in water limited environment.

In WA, soil testing for mineral N (ammonium plus nitrate) has traditionally been taken from the top 0-0.1 m. Farmers and advisors are now interested in deeper soil testing, in order to know how much mineral N occurs at depth and what this may mean in terms of fertiliser N application decisions. Accounting for topsoil and subsoil test level in N fertiliser use varies markedly among growers and advisors depending on; their own historic applications; use of nitrogen decision support tools (N-DSS’s) such as Yield Prophet simulations or SYN. Other growers use approximate total soil profile N and then add N fertiliser required to reach target yield (i.e. 45 kg N/ha for 1 t/ha of grain). The main question this paper is addressing is “Do I need to soil test to depth for better N decisions?” To answer this we needed to understand: 1. Where in the profile the subsoil N occurs and if it is related to topsoil N, 2. How effective is the subsoil in supplying N for the crop – which depends on root access to subsoil N as affected by subsoil constraints and N leaching, 3. What does this mean for N recommendation systems based on soil testing? and 4. Given the seasonal interaction with yield response, will the subsoil N test results reduce the errors in recommendations enough to justify this extra complexity, cost and effort?

Key Messages • Soil acidity, water repellence and root disease have been shown to reduce crop access to soil P and where these constraints are present yield responses to fertiliser P have occurred even where soil test P levels are classed as sufficient. • Assessment of root and soil constraints to soil P availability needs to be integral to the P fertiliser recommendation process.

In south-western Western Australia, the incidence of potassium (K) deficiency in wheat has increased steadily, with two-thirds of the arable lands prone to potassium depletion through continued removal in hay or grain and straw. Leaching of potassium especially in sandy soils, where the total potassium pool is small, is also a significant contributor to poor K-use efficiency in farming systems. Adequate K supply is required for obtaining high crop yield and quality and enhancing the efficiency of other nutrients and the ability of plants to tolerate stresses from soil moisture, salinity, temperature, disease and pests. In this study wheat was grown in grey sand in a glasshouse and treated with six levels of soil potassium supply to assess plant responses during the growing season in terms of plant growth, potassium uptake and yield components.

BACKGROUND: Adolescence is the peak age of onset for mental illness, with half of all people who will ever have a mental illness experiencing their first episode prior to 18 years of age. Early onset of mental illness is a significant predictor for future episodes. However, adolescents and young adults are less likely than the population as a whole to either seek or receive treatment for a mental illness. The knowledge and attitudes of the adults in an adolescent's life may affect whether or not help is sought, and how quickly. In 2007, the Youth Mental Health First Aid Program was launched in Australia with the aim to teach adults, who work with or care for adolescents, the skills needed to recognise the early signs of mental illness, identify potential mental health-related crises, and assist adolescents to get the help they need as early as possible. This paper provides a description of the program, some initial evaluation and an outline of future directions. METHODS: The program was evaluated in two ways. The first was an uncontrolled trial with 246 adult members of the Australian public, who completed questionnaires immediately before attending the 14 hour course, one month later and six months later. Outcome measures were: recognition of schizophrenia or depression; intention to offer and confidence in offering assistance; stigmatising attitudes; knowledge about adolescent mental health problems and also about the Mental Health First Aid action plan. The second method of evaluation was to track the uptake of the program, including the number of instructors trained across Australia to deliver the course, the number of courses they delivered, and the uptake of the YMHFA Program in other countries. RESULTS: The uncontrolled trial found improvements in: recognition of schizophrenia; confidence in offering help; stigmatising attitudes; knowledge about adolescent mental health problems and application of the Mental Health First Aid action plan. Most results were mai