Fundamental changes in farming systems occurred throughout the medium-rainfall zone of southern Australia during the late 1990s. Pulse and canola crops replaced pastures and long-fallowing, and minimal-tillage practices were increasingly adopted. An experiment was established in 1998 to examine long-term effects of these changes on crop productivity and soil fertility. Nine rotation–tillage treatments based on 3- and 6-year cycles were compared by using wheat (Triticum aestivum) as a bioassay crop over 2001–17. Seasonal conditions during the study ranged from the Millennium Drought to the top rainfall decile.

Barley yellow dwarf virus (BYDV) is a phloem-limited virus that is persistently transmitted by aphids and causes significant yield losses in wheat (Triticum aestivum L.). The present study was conducted to investigate the effects of BYDV in wheat on physiological and morphological traits, yield attributes and pasting properties of flour, and to determine any differences for these traits between susceptible and resistant genotypes under BYDV infection. Significant impact on physiological and morphological traits and yield was observed in plants inoculated at the 2-leaf stage (Zadoks scale, Z12), with a greater impact in the three susceptible genotypes than in the resistant genotype. Yield reduction with inoculation at Z12 was 18–49%, and yield reduction with inoculation mid tillering (Z25) was 6–31%. There was a significant reduction in effective tiller number with both inoculation times, but 1000-kernel weight was affected only with early inoculation. Pasting properties were little affected by BYDV infection, with genotype having a larger effect than infection. Grain yield showed negative correlation with tissue-blot immunoassay and visual symptom score, and positive correlation with all gas-exchange parameters, chlorophyll fluorescence, leaf area and biomass weight. The results suggest that stomatal conductance, transpiration rate and chlorophyll fluorescence measurements are suitable for assessment of BYDV infection and for screening BYDV of susceptible and resistant wheat genotypes.

Previous research has shown that ground rubber from tyres can be used to supply fertiliser zinc (Zn) for prevention of Zn-deficiency in crops, and that inoculation of the ground rubber with several bacterial species hastens the release of Zn to the soil. We evaluated the ability of several microbial combinations to speed the release of Zn from ground rubber and to decrease soil pH to favour phytoavailability of Zn to crops. In a batch experiment, treatment combinations of two rates of ground crumb rubber (nil or 300 mg kg^–1, equal to 0 or 3.4 mg Zn kg^–1) and 24 bacterial inoculants were incorporated into a Zn-deficient calcareous soil. In a pot experiment, two wheat cultivars were grown on the soil without or with ground rubber amendment or with equivalent Zn from ZnSO₄ (15 mg kg^–1) in combination with two selected microbial treatments. All microbial treatments significantly decreased soil pH at week 3, most notably the inoculant comprising Rhodococcus erythropolis and Acinetobacter calcoaceticus (RA) + Pseudomonas putida P41 (P1) + mixed Thiobacillus spp. (Mt). In the presence of tyre rubber, soil pH at week 10 was still significantly lower than the initial value, and soil DTPA-extractable Zn concentration increased until week 6 and then remained unchanged or slightly reduced at week 10. The greatest increase in DTPA-Zn concentration occurred with the RA inoculation. Microbial inoculation treatments were classified by cluster analysis into eight groups based on soil pH and concentrations of iron (Fe) and Zn. Group 8 produced the lowest pH and highest concentrations of DTPA-Fe ( average 6.92 mg kg^–1) and DTPA-Zn (average 2.67 mg kg^–1). Inoculations with RA and with RA + P1 + T. thioparus were the most effective in hastening an increase in DTPA-extractable Zn and significantly enhanced Zn uptake by wheat plants, whereas inoculations with P. putida P168 and with RA + P2 + Mt were most effective in decreasing soil pH and increasing plant Fe concentration.

The role of exogenous individual or combined application of silicon (Si) and salicylic acid (SA) (control, 6 mm Si, 1 mm SA, and 6 mm Si + 1 mm SA) on grain yield and some key physiological characteristics of wheat (Triticum aestivum L.) cvv. Shiraz (drought-sensitive) and Sirvan (drought-tolerant) was investigated under field water-stress conditions (100% and 40% field capacity). Drought stress caused a considerable reduction in biological yield, yield and yield components, relative water content and leaf water potential of both cultivars. Application of Si and SA effectively improved these parameters in water-deficit treatments. Moreover, water-limited conditions markedly promoted the activities of key antioxidant enzymes including peroxidase, ascorbate peroxidase, catalase and superoxide dismutase as well as the levels of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂), while enhancing the accumulation of soluble sugars, potassium, magnesium and calcium in leaf tissues. Application of Si and SA further enhanced the activities of the key antioxidant enzymes and accumulation of osmolytes, and decreased the levels of H₂O₂ and MDA in drought-stressed plants; the positive effects of Si were greatest when it was applied with SA. Synergistic effects of Si + SA application on yield and physiological parameters were apparent compared with Si or SA applied separately. Water-stress alleviation and yield improvement in the wheat cultivars by Si and SA application was attributable to partly improved osmotic adjustment and antioxidant activity as well as to more favourable water status under stress conditions. Overall, Si and SA application proved to have great potential in promoting grain yield of wheat in drought-prone areas.

Subsoil manuring is a practice that involves placing high rates of organic amendments in bands at the base of rip-lines that extend down into the subsoil to a depth of 30–40 cm, in order to ameliorate poorly structured clay subsoils. The objective of this study was to determine whether the increases in crop yield from this practice, which occurred at one site in the high-rainfall zone in Victoria from 2005 to 2007, would occur at other sites and in other seasons in south-western Victoria. On-farm field experiments were therefore carried out at three sites in south-western Victoria between 2009 and 2012 to measure the yield responses to subsoil manuring. The study found that subsoil manuring with poultry litter resulted in consistent and recurring increases in estimated grain yield at these sites, with responses occurring with consecutive crops. Increases in estimated grain yield continued for 4 years, with average increases in hand-harvested yield of 3.5 t ha^–1 for wheat, 1.6 t ha^–1 for canola and 2.3 t ha^–1 for faba beans. The estimated increases in grain yield were frequently associated with the increased extraction of deep subsoil water after anthesis. A treatment involving deep-banded nitrogen (N) and phosphorus (P) fertilisers and additional in-crop N, which matched the N and P in the poultry litter, yielded less than the full rate of subsoil manuring in seven of the eight site-years. This suggests that yield responses from subsoil manuring were not solely due to the release of N and P from the deep-banded poultry litter.

Net form of net blotch (NFNB), caused by Pyrenophora teres f. teres, is a major foliar disease of barley (Hordeum vulgare L.) worldwide that can cause grain yield and quality loss in susceptible varieties. Seed- and foliar-applied fungicides were evaluated in six field experiments infected with NFNB during 5 years, for suppression of NFNB severity and protection of grain yield and quality. Suppression of NFNB severity varied between treatments and experiments. Grain yield and quality improvements were recorded in two experiments. Foliar fungicide applications at stem elongation (Zadoks growth stage Z31) and flag leaf emergence (Z39) or ear emergence (Z55) significantly reduced NFNB severity, increased grain yield by up to 23%, and improved grain-quality measurements of retention, screenings and weight. The seed-applied fungicide fluxapyroxad provided significant reductions in NFNB severity, improvements in grain yield of up to 20%, and improved grain quality. Where NFNB was severe, none of the seed or foliar fungicide application strategies provided complete control of NFNB, indicating that more than two applications were necessary when conditions were favourable for disease development in susceptible varieties.

Among the forage species cultivated in South America, the genus Urochloa is the most used, and the cultivar Marandu of U. brizantha is the most widely planted in Brazil. The objective of this study was to evaluate forage performance in association with Azospirillum brasilense, combined with nitrogen (N) fertilisation. The study was conducted under field conditions in Araguaína, Tocantins, in the central region of Brazil, between March 2016 and March 2017. Four N fertiliser rates (0, 12.5, 25 and 50 kg/ha of N per cutting cycle) were combined with two inoculation treatments (inoculated and non-inoculated), with evaluations carried out in three periods of the year (transition, dry and wet seasons). Marandu grass plants inoculated with A. brasilense had greater plant height, number of tillers and forage production than non-inoculated plants, regardless of the N rate. Inoculation with A. brasilense allowed a 20% reduction in N fertilisation. Our results indicate that inoculation with A. brasilense in Marandu grass, as well as increasing forage production, can help to mitigate the stresses caused by the dry season.

The aim of the study was to evaluate the effect of nitrogen (N) fertilisation on certain quality parameters and in vitro total gas and methane production of improved grass species commonly used as fodder species in South Africa. Treatments included seven grass species representing two photosynthetic pathways (C₃ and C₄) with three levels of N fertilisation (0, 50 and 100 kg N ha^–1). Plants were grown in a greenhouse and N was applied in a single application after a simulated defoliation. Sample material was harvested by hand after an 8-week regrowth period. Grass species and rate of N fertiliser both had effects (P < 0.05) on the nutritive value and in vitro organic matter digestibility of the selected species. Crude protein concentration increased (P < 0.05) and neutral detergent fibre concentration tended to decrease as the level of N fertilisation increased for both C₃ and C₄ species. Generally, no effect was found of N fertilisation on in vitro total gas or methane production; however, increasing the level of N fertiliser increased (P < 0.05) the methanogenic potential (in vitro methane/in vitro total gas production) of D. glomerata, F. arundinacea and C. ciliaris after a 24-h incubation period but no significant effects were reported after a 48-h incubation period.

Herbicide resistance is a common occurrence in southern Australia. The evolution of herbicide resistance is influenced by the selection pressure placed on the weed species controlled by that herbicide. Results from resistance screening of ∼4500 annual ryegrass (Lolium rigidum Gaud.) samples were entered in a GIS database, together with several agricultural parameters used in the Australian Bureau of Statistics Agricultural Surveys. This allowed a study of the associations between mode of action of resistance, geographic distribution of resistance across southern Australia, and farming practices employed in particular regions.

The effect of prolonged drought treatments on persistence, growth traits, drought survival and post-drought recovery was investigated in two sets of differently managed genotypes of cocksfoot (Dactylis glomerata L.). In total, 72 genotypes (two sets of 36 managed for seed and forage harvest, respectively) were evaluated for agro-morphological traits in the field during 2013–15 under normal and deficit irrigation regimes. In the fourth year (2016), irrigation was withheld in both irrigation treatments for 2 months and then plants were re-watered to investigate the effect of prolonged drought regimes on traits related to post-drought recovery. The deficit irrigation regime decreased persistence and recovery. These reductions were lower in the seed-management than the forage set, which indicates that delaying the first harvest of the seed-management treatment to maximise seed production led to lower impact of drought stress. The seed-management treatment also had lower persistence. The forage-management treatment had higher recovery under normal irrigation, whereas under deficit irrigation, the seed-management treatment had higher recovery. Association analysis showed the possibility of selecting genotypes having high values of persistence and drought tolerance. Results also showed a negative correlation between days to flowering and recovery after drought, indicating that selection for earliness may improve survivability and persistence of these plants. Superior genotypes with higher forage production and better recovery, persistence and drought tolerance may be recommended for development of synthetic cultivars.