John Howieson

Deep sand soils are inherently fragile with surface layers that are very low in organic matter and clay. Previous studies demonstrate that strategic deep tillage such as soil inversion and deep soil mixing can increase crop production on these soils in Southern Australia. However, the majority of the organic matter and nutrients are concentrated in the top organically stained layer and deep tillage incorporates 50-60 % of the organic layer into the subsoil below 200 mm. The physical composition of the soil (percentage of sand, silt, clay and organic matter) and the chemical properties of the soil (pH, nutrient levels, cation exchange capacity) can strongly influence the soil adsorption of trifluralin. Modest levels of organic matter and clay particles in the topsoil particularly following deep tillage equate to the scant attenuation of herbicides on sandy textured soils. Soil samples (0-100 mm) were collected from three experimental sites; two Arenic Solonetz soils near Esperance and one Arenic Arenosol soil near Geraldton in Western Australia. At all three sites, three experimental treatments were sampled; control (no tillage), deep mixed with a spader to 350 mm and soil inversion with a mouldboard plough to 350 mm. Soil samples were taken on two growing seasons post tillage at Geraldton, three post tillage at Esperance TJM and twelve post tillage at Esperance E1. Tillage reduced the measured soil-liquid partition coefficient (Kd) of trifluralin (p <= 0.05) at all three experimental sites. A greenhouse bioassay was developed to determine if soil changes from strategic tillage at one of the Esperance sites and the Geraldton site could be directly related to herbicide bioavailability at two of the experimental sites. Intact cores were used to maintain integrity of the field soils. Cores from both field sites demonstrated that soil inversion reduced the effective dose of trifluralin (p <0.01) for the bioassay species Lens culinaris. Together these experiments illustrate that strategic deep tillage can increase the bioavailability of trifluralin. These findings offer a valuable insight into the soil behaviour of trifluralin and can help farmers estimate the risk of phytotoxicity based on measurable soil characteristics.

Physical dormancy in seeds is caused by a water-impermeable seed coat. It plays a crucial role in the sustainability of ley farming systems in Mediterranean climates by enabling pasture legumes to regenerate from a soil seed bank. Sophisticated management of the pattern of physical dormancy break can synchronize germination of plants with the optimal growing season, essential to the sustainability of the system. The ability of the maternal plant to reproduce and provide its progeny (seed) with sufficient resources is influenced by both genetic and environmental factors. However, when abiotic (e.g., drought, temperature) or biotic (e.g., pests, diseases) stressors affect the maternal plant during its reproductive phase, the allocation of resources to seeds can vary, leading to variability in physical dormancy outcomes. This genetic × environment interaction is well documented; however, a third factor, management, is less understood. Herein lies a significant knowledge gap, and this is the first review that examines physical dormancy from an agricultural management perspective. In the manuscript, we explore the evolution of physical dormancy in pasture legumes in ley farming systems and how the intensification of agricultural management practices inadvertently affects physical dormancy development and the pattern of release. This intensification threatens the sustainability of ley farming by changing the timing of physical dormancy release, which concomitantly occurs under changed climatic conditions. Therefore, climate change combined with the intensification of agricultural management practices, including pesticide use, altered grazing regimes, and frequency of crop rotation, poses significant challenges to physical dormancy regulation and soil seed bank dynamics in ley farming. We suggest that to combat the impacts of agricultural intensification, detailed studies and breeding programs should focus on selecting legumes with both agricultural and climatic resilience for successful adaptation to evolving agricultural landscapes and ensure continued sustainable productivity.

Context or problem
Selective herbicides control weeds in cereal crops and break down over time, allowing safe planting of legumes in the following years. However due to climatic inconsistencies and changing farming practices, this is not always the case, and residues can inhibit formation of legume/rhizobia symbioses.

Objective or research question
The objectives were to determine whether: i) exposure to triasulfuron, even at extremely low levels, reduces shoot and root growth and nodulation of five diverse and widely sown legume pasture cultivars in Australian farming systems; and ii) sowing legumes prior to recommended plant-back criteria being met for chlorsulfuron, triasulfuron herbicide, clopyralid, and pyroxasulfone herbicides results in unacceptable damage to subsequently sown pasture and crop legumes, causing reduced root and shoot growth, nodulation and N fixation.

Methods
A series of glasshouse and field experiments explored herbicide residue impact on commonly used legumes in dryland farming systems.

Results
A glasshouse study determined triasulfuron at concentration 0.000225 g a.i/ha, a (1/100,000) dilution of the label rate caused significant (p < 0.001) decrease in nodule count, root length, root, shoot weight for Trifolium spumosum cv. Bartolo and T. subterraneum cv. Dalkeith, and at 0.225 g a.i/ha and 2.25 g a.i/ha for all five cultivars tested. A bioassay assessed T. subterraneum cv. Dalkeith health when grown in field soil-cores taken 4, 7 and 10 months after herbicide application (chlorsulfuron, triasulfuron, clopyralid and pyroxasulfone) to a wheat crop. For all three, herbicide residues significantly decreased (p < 0.001) nodule number, shoot weight, root length and whole plant weight of T. subterraneum cv. Dalkeith compared to control. A field experiment assessed nodulation of five pasture and two crop legumes sown dry (dormant summer sowing), or following rainfall 10.5 months after initial herbicide application. Nodulation of all legume cultivars decreased in plots treated with clopyralid. Chlorsulfuron decreased nodulation for all cultivars except T. glanduliferum and T. subterraneum. Triasulfuron reduced nodulation for all cultivars except Ornithopus sativus and T. spumosum. Pyroxasulfone decreased nodulation of Biserrula pelecinus cv. Casbah and Lupinus angustifolius cv. Mandalup.

Conclusions
Herbicide residues from preceding cereal crops reduced fitness and symbiotically fixed N in subsequently sown pasture or crop legumes.

Implications or significance
Our study highlighted label plant-back recommendations should be strictly adhered to, despite conflict with modern farming approaches of dry or early sowing) to combat climate change. This outcome may consequently lower profitability and increase the carbon footprint of farming systems.

Wheat proteins provide around 20% of all human dietary protein, but their end-use qualities are determined by the form and quantity of nitrogen in the endosperm. In the developed world, there is a heavy reliance in grain production on nitrogen supplied from synthetic fertilisers, and this fertiliser can contribute up to 50% of the on-farm emissions of greenhouse gasses in agriculture. However, despite increasing rates of application of synthetic nitrogen to cereals, wheat grain protein levels, in developed nations, have been frequently failing to reach the premium grade required by the bread-making market. Here, for the first time, we report that biological nitrogen fixation from a new generation of hardseeded annual forage legumes, when grown in rotation with cereal crops, can replace fertiliser N without compromising grain protein. The forage legumes were grown in rotation with Triticum aestivum, and compared with rotations that included a fallow, or a cereal crop at three rainfed sites in Western Australia with differing soil types for 2–4 years. The wheat received low, medium and high rates of urea to indicate if forage legumes can provide sufficient nitrogen for sustainable wheat production. At all sites and years studied, we discovered that cereal grains produced following a year of forage legumes had significantly higher protein levels than when grown as part of a continuous cereal rotation. These results were achieved in combination with a reduction in on-farm emissions (by over 200 kg/ha of CO2) without compromising yield as indicated by emissions accounting. Including appropriate forage legumes in farming systems allows production of low emission intensity grain proteins in dryland farming.

The sandplain soils of WA are inherently fragile with surface layers that are very low in organic matter and clay content. The advent of minimum- and no-till farming has seen the increase in frequency and intensity of cropping on these soils. However, a combination of soil physio-chemical constraints and agronomic issues remain a challenge to the sustainability of cropping systems on them. These constraints include sub-soil compaction, soil water repellence, sub soil acidity and herbicide resistant weeds. Strategic deep tillage such, as soil inversion and deep soil mixing, have been shown to ameliorate these multiple constraints and dramatically increase crop production. For WA soils, an increase in herbicide usage is correlated with a decrease in regular tillage, and how the two interact is imperfectly understood. As a result, current herbicide strategies and rates are designed to perform optimally in a minimum tillage environment. Two field experiments were established to compare crop damage from a range of commonly used pre-emergent herbicides when grown in soil that remained under minimum tillage, was deep mixed or inverted. These trials demonstrated that both strategic tillage methods significantly changed the soil surface composition that would be expected to directly affect the bioavailability of some herbicides. Two commonly used herbicides, Metribuzin and Diuron, detrimentally impacted crop performance following tillage in both trials. These same treatments reduced yield by a greater extent on both the soil inversion and deep mixing treatments (p < 0.001). No other herbicides, when applied at either label or triple label rates, significantly impacted yield on any of the soil treatments. There was a substantial crop production benefit from strategic deep tillage at Esperance but not at Geraldton. These results reflect that the influence of deep tillage on the toxicity of herbicides is highly dependent upon soil properties and rainfall.
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The use of rhizobiumRhizobium inoculants for improvement in nitrogen-fixationNitrogen and productivity of grainGrainlegumesLegume has been well established in developed countries. However, the practice is still under-utilized in NigeriaNigeria. NitrogenNitrogen (N) is the most frequently deficient nutrient for crop production, while nitrogenNitrogenfertilizersFertilizers are costly, inadequate, and may not be timely in supply. These make rhizobia inoculants a cheaper, easier and safer option to improve the N2-fixation and productivity of grainGrainlegumesLegume. Inoculant use in NigeriaNigeria was initiated in the 1970s, but still remains very limited. Studies conducted on inoculant use were initially on “US type” SoybeanSoybean (Glycine max (L.) Merrill), which has been found to require specific inoculation with Bradyrhizobim japonicum for optimum productivity. Studies were also conducted on inoculation of cowpeaCowpea (Vigna unguiculata (L.) Walp), but rarely on bambara groundnutGroundnut (Vigna subterranea (L.) Verdc.) and groundnutGroundnut or peanutPeanut (Arachis hypogaea L.). In the 1980s, the International Institute of TropicalTropicalAgricultureAgriculture (IITA) Ibadan, NigeriaNigeria, introduced promiscuous soybeanSoybeancultivarsCultivars; TropicalTropical Glycine Cross (TGx). These genotypesGenes nodulate freely with the indigenous rhizobiumRhizobium population, fix large amount of atmosphericAtmospherenitrogenNitrogen and produce higher grainGrainyieldsYields than the localLocal genotypes. However, some experiments indicated up to 40–45% increases in yieldYields by some of the genotypesGenes on inoculation. Hence, the ultimate solution remains the development of inoculants using highly effective indigenous rhizobia strains for particular crops. The recent efforts of the project “Putting NitrogenNitrogenfixationNitrogen fixation to work for smallholder farmersFarmers in Africa (N2Africa)Africa” towards the promotion of inoculants technology are highly welcomed in the country.

Regular seafood consumption plays a protective role against chronic conditions and obesity, which account for the majority of the burden of disease in Australia. Despite public health recommendations, Australians consume less than the recommended levels of omega-3s (n-3) to reduce the risk of chronic disease. The best source of long-chain n-3 is oil-rich fish.

This paper reports on results from a community survey on attitudes and patterns of seafood consumption conducted in a coastal town in Western Australia. Data were collected through a self-administered questionnaire and 300 valid responses were received (60.7% aged 55 years or over; 65.7% female).

Weekly patterns of seafood consumption were observed. Almost all participants (93.7%) thought seafood was an important part of a healthy, balanced diet. Overall, participants (73.3%) did not perceive seafood as inconvenient to prepare, and had a high level of confidence around cooking and serving seafood. There were no gender or age differences in confidence except for those aged under 30 years with only a third (36.4%) expressing confidence in cooking and serving. All participants, across all ages and genders (78.7–90.7%) made informed decisions when purchasing seafood and they sought more point-of-sale information. They identified affordability, availability, easy-to-understand food labels and quick-and-easy recipes at point of purchase as the main enablers towards increased seafood consumption.