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Context: Herbicide-resistant annual ryegrass (Lolium rigidum ; ARG) is a major weed of commercial significance globally, including no-till wheat-based production systems in south-eastern Australia. Aims: To compare the cost-effectiveness of different crop sequences and intensities of weed management to control ARG in rainfed grain production. Methods: Two on-farm studies in southern New South Wales, Australia, compared the effect of combinations of 3-year crop-sequence options (continuous wheat, 1- or 2-years of break crops), conservative or aggressive weed-control measures, hay cuts, legume brown manure (BM), and/or weed-free winter fallow on in-crop ARG infestations and soil seedbanks. Gross margins were calculated for each combination of treatments to compare system economic performance. Key results: Double-breaks consisting of two consecutive broadleaf crops, or canola–cereal hay, were frequently the most profitable and effective ARG control strategies. Single canola or lupin crops, BM, cereal hay, and fallow all significantly reduced subsequent in-crop ARG and seedbank numbers compared with continuous wheat. Aggressive in-crop control measures in wheat were more expensive than those applied to break crops. Gains in ARG control could be lost by a single year of poor weed control. Conclusions: High levels of control (>95%) over three consecutive seasons are required to reduce ARG seedbanks, and this is most cost-effectively achieved with diverse crop sequences. Implications: Farmers with high populations of ARG can reduce seedbanks by growing three crops sequentially that achieve complete weed seed control. This must be followed with ongoing high levels of control in subsequent years to keep ARG seedbanks low. The paper reports the outcomes of two on-farm experiments that aimed to identify the most cost-effective strategies to control herbicide-resistant annual ryegrass in rainfed, no-till, wheat-based farming systems in southern NSW. The studies linked efficacy of annual ryegrass control with the relative profitability of combinations of different crop sequences and agronomic management. The results showed that three consecutive years of >95% weed control by using diverse crops are required to cost-effectively reduce annual ryegrass seedbanks in soil to manageable levels. [ABSTRACT FROM AUTHOR]

Context: Lolium rigidum Gaudin (annual ryegrass) has remained the most problematic weed of crop production in Australia for more than 20 years. There is some evidence that this weed species can rapidly adapt to management practices including delayed crop sowing. Aims: Studies were undertaken to determine genetic variation for seed dormancy within L. rigidum populations and its association with genes involved with gibberellic acid and abscisic acid synthesis. Methodology: Populations of L. rigidum were grown in pots to select low and high dormancy cohorts. Seeds produced by these cohorts from each population were assessed for variation in seed dormancy. Seeds of high and low dormancy cohorts were concurrently assessed for seed dormancy and expression of LrABA1 and LrGA20ox genes, using quantitative real-time PCR. Results: Presence of differences greater than two-fold in seed dormancy between populations from the same farm indicated in situ selection for seed dormancy, most likely in response to management. Low and high dormancy cohorts of all populations maintained clear differences in seed dormancy in both years of assessment. Differences in seed dormancy between low and high dormancy cohorts were significantly correlated with LrABA1 and LrGA20ox gene expression. Conclusions: This investigation has provided clear evidence of the presence of genetic variation for seed dormancy within L. rigidum populations. Implications: The presence of genetic variation for seed dormancy in L. rigidum populations will allow this weed to adapt rapidly to changes in weed management practices such as delayed sowing of crops. Lolium rigidum is one of the most problematic weeds of cereal crops in southern Australia. Seed dormancy of different L. rigidum populations was analysed, and genes responsible for the control of seed dormancy were identified. Findings from our research enhance understanding of the genes involved in regulating seed dormancy, their expression over time, and how loss of dormancy is associated with changes in gene expression. [ABSTRACT FROM AUTHOR]

Context: Annual ryegrass (Lolium rigidum) is a major weed of crop production in southern Australia that readily develops resistance to herbicides. Resistance increases both yield losses and control costs associated with this species. Aims: This study aimed to gauge the extent and distribution of resistance to herbicides in L. rigidum across south-eastern Australian grain production systems by collecting seed from randomly selected fields. Methods: A total of 1441 weed populations were collected through random surveys conducted over 5 years across 13 agricultural regions of four states with these samples then tested for resistance to eight herbicides from six modes of action. Key results: Resistance to diclofop-methyl and sulfometuron-methyl was most common, being present in 64% and 63% of populations respectively. Glyphosate resistance was present in 4% of populations collected. Only 15% of populations collected were susceptible to all herbicides tested. Large differences in resistance occurred between the 13 regions surveyed with resistance to diclofop-methyl ranging from 15% to 86% of populations and sulfometuron-methyl from 12% to 96%. Resistance to post-emergent herbicides tended to be higher than pre-emergent herbicides. Multiple resistance was common with 60% of populations collected having resistance to two or more herbicide modes of action. Conclusions: There were significant differences in the extent of multiple resistance in L. rigidum populations collected from individual regions suggesting that the rates of resistance evolution have differed between regions. Implications : The high incidence of herbicide resistance in L. rigidum populations randomly collected from south-eastern Australian cropping fields highlights the need for the adoption of additional weed control practices to mitigate the impact of this species on grain production systems. Herbicide resistant weeds are a major threat to crop production, with annual ryegrass being the major species of concern in Australia. Surveys of south-eastern Australia conducted over a 5 year period found over 60% of populations were resistant to two or more herbicide groups and only 15% of ryegrass populations were susceptible to all tested herbicides. The high level of resistance found across south-eastern Australia highlights the need for farmers to adopt non-herbicide practices, in conjunction with herbicides, to control this species. [ABSTRACT FROM AUTHOR]

Livestock is a major component of agriculture, and a continuous supply of nutritious forage/fodder is necessary for sustainable livestock production. Zinc (Zn) deficiency is a global concern for human as well as animal health, but Zn fertilisation for productivity and biofortification of forages is not well understood. Therefore, a 2-year field study was conducted to investigate the influence of soil-applied ZnSO4 on morphological traits, yield, nutritional quality and Zn biofortification in four forages. The grass forages (oat, barley, annual ryegrass and triticale) were factorially combined with four levels of soil-applied ZnSO4 (0, 5, 10 and 15 kg ha−1) and two harvesting stages (booting and 50% heading). The treatments were arranged in a triplicate randomised complete block design with a split–split plot arrangement where grass forage species were kept in main plots, ZnSO4 application in subplots and harvest stage in subsub plots. ZnSO4 fertilisation significantly improved morphological traits, dry-matter yield, crude protein, acid detergent fibre (ADF) and shoot Zn concentration in all grass forages at both harvesting stages. Best performance for yield, quality traits, and Zn contents across all crops was observed where ZnSO4 was applied at 15 kg ha−1 and harvested at 50% heading stage. The highest economic returns were provided by triticale and annual ryegrass with 15 kg ZnSO4 ha−1 harvested at 50% heading. In conclusion, for a profitable forage production with good nutritional quality and Zn biofortification, triticale and annual ryegrass may be recommended with a 15 kg ZnSO4 ha−1 fertilisation. Zinc (Zn) deficiency is a global concern for human as well as animal health, but Zn fertilisation for productivity and biofortification of forages is not well studied. In our experiment, ZnSO4 fertilisation (15 kg ha−1) improved morphological traits, dry biomass yield, nutritional quality and straw Zn concentration of triticale, barley, oat and rye grass forage. In conclusion, a 15 kg ZnSO4 ha−1 fertilisation may be recommended to obtain higher fodder yield, forage quality and Zn biofortification in grass forages in semi-arid regions. [ABSTRACT FROM AUTHOR]

Perennial ryegrass (Lolium perenne L.) is a widely sown pasture species in temperate regions. Under heat and moisture-deficit stress, its production is suppressed and tiller mortality increases, particularly when plants are simultaneously exposed to other stresses such as intense defoliation. We investigated the effects of extended grazing exclusion periods in spring and summer on herbage and soils of rotationally grazed, perennial ryegrass-dominant pastures at a summer-wet site and a summer-dry site in sheep and beef hill country in New Zealand. Treatments comprised 'grazed' (conventional rotational grazing), 'early opening' (grazing exclusion from mid-spring to mid-summer to allow perennial ryegrass to flower), and 'deferred grazing' (grazing exclusion from mid-spring to late summer to allow perennial ryegrass to flower and set seed). At both sites, deferred grazing increased perennial ryegrass tiller density and total vegetation cover, and reduced the abundance of broadleaf species and Pseudopithomyces chartarum spores for up to 15 months after exclusion compared with the grazed control. Herbage production was reduced during the deferred period but there was a growth surge thereafter so that herbage production over the study period was similar in the deferred and grazed treatments. Pasture nutritive values were lower in the deferred than the grazed treatment during the exclusion period but were similar in all treatments by the end of the following winter. In the autumn after deferring, seedlings contributed ~50% of the perennial ryegrass tillers present at the summer-dry site but only ~10% at the summer-wet site, where regrowth tillering of existing plants contributed a high proportion of the perennial ryegrass tillers present. Overall, early opening had few effects on the pasture, whereas deferred grazing had numerous positive effects on the pasture but only short-term effects on soil quality. We investigated the impacts of deferred grazing (livestock excluded from mid-spring to late summer to enable perennial ryegrass to flower and set seed), early opening (livestock excluded from mid-spring to early summer to enable perennial ryegrass to flower) and standard rotational grazing on hill country pastures and soils under beef and sheep grazing. Compared with standard rotational grazing, deferred grazing had positive effects on pasture productivity but only short-term effects on soil quality, whereas early opening had few effects on the pastures or soils. [ABSTRACT FROM AUTHOR]

In northern Victoria, Australia, perennial pastures for the dairy industry have historically been based on perennial ryegrass. However, perennial ryegrass does not perform well under high summer temperatures and water stress. We investigated irrigation, renovation and grazing management strategies for improving the resilience and survival of perennial ryegrass over summer on two farms in northern Victoria over 2.5 years. At each farm, two irrigation bays were sown in March 2015. During summer (late December–mid-March), one bay was not irrigated and the other bay received a single mid-summer irrigation. Each bay was sown to 12 ryegrass cultures: five cultivars of perennial ryegrass either oversown or not oversown, and two oversown cultivars of short-lived ryegrass (SLRG). A mid-summer grazing treatment was applied to one-half of each of these plots. All plots at both sites received the same irrigation and grazing management at other times of the year. There were significant variations in dry matter (DM) production, nutritive characteristics and plant frequencies across sites and seasons, and across renovation, irrigation and grazing management strategies. Cumulative DM yields were higher in the perennial ryegrass than the SLRG cultivars. Summer DM removal was very low at both sites; the ungrazed plots recovered and produced more DM in the following cooler period than the grazed plots in the first year but not the second. Metabolisable energy concentration was higher for perennial ryegrass than SLRG cultivars and was also higher in plots that had been grazed over the summer. There were large differences in plant frequency between species, and there were some differences among perennial ryegrass cultivars. The effect of summer grazing on plant frequency varied at each site and was not significant within an irrigation treatment. This research confirms that perennial ryegrass is not well suited to the hot, dry summers of northern Victoria and suggests that, under conditions of limited summer irrigation, farmers should focus on plant survival rather than summer yield if they are to maximise annual DM production. The effects of restricted irrigation and summer grazing were examined in plots of perennial and short-lived ryegrass cultivars at two district sites in northern Victoria, Australia. Responses varied across sites, seasons and cultures. Perennial ryegrasses performed better than short-lived ryegrasses, but dry matter production was low and plant frequency was a better indicator of plant resilience to these conditions. [ABSTRACT FROM AUTHOR]

Previous research demonstrated that the interval between defoliation treatments based on the leaf stage is a promising tool for the management of annual ryegrass (Lolium multiflorum L.) pasture. The use of this tool, which is based on the physiological status of the plant, could also benefit the seed production. We assessed the effects of the time of defoliation based on leaf stage on seed yield and quality of annual ryegrass cut to three residual stubble heights (RSH) (50%, 25% and 0% of plant height pre-defoliation) and a second defoliation applied to certain treatments based on the leaf stage of the plant regrowth (two or three leaves per tiller). Higher defoliation intensities (lower RSH) increased the amount of harvested forage to 4.0 t DM ha-1. Moderate defoliation (50%) undertaken at the 3-leaf stage combined with intense defoliation (25% and 0%) at the 2-leaf stage resulted in the highest seed yields (1.8 t ha-1). However, lower RSH reduced mean seed weight and physiological seed quality, which was also associated with lower seed starch and protein content. Accelerated ageing (AA) tests were used to compare seed vigour between treatments. A second defoliation at the 3-leaf stage plus intense defoliation (RSH 0%) resulted in seed lots with a high rate of lipid peroxidation after the AA test, followed by lower catalase activity, germination, and seedling growth. The combination of a second defoliation at the 3-leaf stage and the retention of higher RSH (50%) promoted a greater proportion of leaf blades in the stubble, with a strong positive correlation with seed production and vigour. Antioxidant enzyme activity after the AA test is an important marker of annual ryegrass seed quality. [ABSTRACT FROM AUTHOR]