Phosphorus (P) deficiency and aluminium (Al) phytotoxicity are major limitations for crop yield in acid soils. To ameliorate such limitations, agricultural management includes application of lime and P fertilisers, and the use of Al-tolerant plant genotypes. The mechanisms of Al tolerance and P efficiency may be closely related through strategies that decrease the toxicity of the Al³ ion and increase P availability in soils. However, the effects of soils with high Al saturation on P acquisition by wheat have been little studied under field conditions. The aim of this work was to study Al–P interactions on wheat genotypes of contrasting Al tolerance when grown under field conditions in a volcanic soil with high Al saturation (32%) and low pH (5.0). A field-plot experiment was performed with winter wheat genotypes, two Al-tolerant (TCRB14 and TINB14) and one Al-sensitive (STKI14), with application of 0, 44 and 88 kg P ha^–1. At the end of tillering and after physiological maturity (90 and 210 days after sowing), plants were harvested and yield and P and Al concentrations in shoots and roots were measured. Soil acid phosphatase, root arbuscular mycorrhizal (AM) colonisation, AM spore number and soil glomalin were determined. Shoot and root production and P uptake were higher in Al-tolerant genotypes than the sensitive genotype. In addition, root AM colonisation and soil acid phosphatase activity were also higher in tolerant genotypes. By contrast, Al concentration in shoots and roots was higher in the sensitive genotype with a concomitant decrease in P concentration. Grain yield of Al-tolerant genotypes was higher than of the Al-sensitive genotype with and without P fertiliser. Overall, the Al-tolerant genotypes were more effective at P acquisition from soil as well as from P fertiliser added, suggesting that plant traits such as Al tolerance, P efficiency, and AM colonisation potential co-operate in overcoming adverse acid soil conditions.

Septoria leaf blotch (SLB), caused by Mycosphaerella graminicola, reduces yield and grain quality of wheat (Triticum aestivum L.) by affecting the photosynthetically active area of the crop. This might influence grain protein concentration (GPC) and affect bread-making parameters. Nitrogen (N) fertilisation is required to achieve high yields in wheat; however, it may enhance the development of foliar diseases such as SLB. The aim of this study was to evaluate the effect of fungicide and N rate on SLB severity, green-leaf-area duration, grain yield and bread-making parameters in three wheat cultivars differing in bread-making characteristics. Two field experiments were conducted during 2009 and 2010 in a split-split-plot design with three fungicide treatments (triazole, triazole–strobilurin, nil) as main plots, three N fertiliser rates as subplots and three cultivars as sub-subplots. Fungicides significantly reduced the area under disease-progress curve (AUDPC) and this was associated with increased yield, which varied among cultivars. The AUDPC was lower in the higher N-rate treatments. Fungicide applications and increasing N rates extended green-leaf-area duration. GPC increased in untreated plots and it was reduced with applications of triazole–strobilurin fungicide. GPC reduction caused by this type of fungicide tended to be lower when the rate of N increased. The two cultivars with low bread-making characteristics showed a tendency to greater reductions in GPC with both fungicide types. Regarding quality variables, only tenacity and dough strength were reduced by the triazole-strobilurin fungicide. On average, for all treatments, tenacity, water absorption and dough development time were higher in the best quality group cultivars.

Wheat streak mosaic virus (WSMV) has become a re-emerging pathogen in recent years in the Czech Republic. Crop (e.g. wheat, barley, maize) and non-crop grasses from the Poaceae family are the natural hosts of the virus. Here, we report the results from coat protein (CP) gene-sequence analysis of WSMV isolates from wheat crops (four cultivars: Turondot, Bodyček, Avenue, Hymack) and three grass species (Agropyron repens, Phleum pratense, Poa pratensis). Phylogenetic reconstruction of putative CP sequences showed that all tested isolates clustered with existing type B isolates of WSMV (originating from Europe and Asia) rather than type D (originating from USA, Argentina, Australia, and Iran) and type A (originating from Mexico) isolates. Analysis of recombination events showed that Turondot and Hymack isolates recombined with P. pratense, whereas Bodyček and Avenue isolates recombined with a type B isolate (Iran_Saadat-Shahr). The grasses A. repens, P. pratense and P. pratensis share recombination events with type A (Mexico_El Batán), type B (French and German isolates) and type D (Iran_Naghadeh) isolates. The characteristic GCA (Gly276) triplet codon found in type B isolates was conserved in both the wheat and grass isolates. Notably, nucleotide variations were mainly observed at positions nt 381–389, nt 405–460 and nt 486–497 between crop and non-crop hosts. Based on our analysis, we propose that the grass isolates form subtype B1 within the type B isolates of WSMV. Putative CP amino acid sequences in the centre of the protein and in the C-terminal domain (aa 112–260) were significantly more frequently conserved in both wheat and grasses than those in the N-terminal domain (aa 11–80). Collectively, these results indicate that variations exist between crop and non-crop hosts of WSMV.

Knowledge on the growth of rice (Oryza sativa L.) in low-fertility field conditions is essential to ensure their sustainability and enhance productivity. The key variables determining the productivity of such systems were studied in 40 recommended rice varieties grown in a low-fertile field. The paddy field had received no form of fertiliser or straw for the past 40 years, but it was used for rice cultivation two times per year under other standard crop-management practices. Harvests were made at 6 weeks after planting and at physiological maturity. The same varieties were also grown for 14 days in glass boxes containing distilled water only. Stepwise regression was used to identify the important variables for predicting dry weight (DW) at 14 days, 6 weeks and maturity. Thousand-seed weight and seed phosphorus (P) content of seed paddy (grains used for planting) had strong positive correlations with DW of seedlings after 14 days (r = 0.91, P < 0.0001) and 6 weeks (r = 0.7, P < 0.0001), respectively. However, initial growth performances did not correlate well with aboveground DW or grain yield at maturity. DW at maturity positively correlated with time taken to maturity (r = 0.78, P < 0.0001), shoot K content (r = 0.28, P = 0.008), root DW (r = 0.22, P < 0.02), and uptake rates of K (r = 0.32, P < 0.01) and P (r = 0.33, P < 0.01) at 6 weeks. Seed N concentration decreased (r = −0.63, P < 0.001) and growth rate increased (r = 0.65, P < 0.001) with time taken to maturity. Although seed weight and seed P content of rice are key determinants of early crop establishment, capacity to produce large roots, amount of K taken up, P and K uptake rates at 6 weeks, and time taken to maturity are the key determinants of maturity biomass and grain yield in low-fertile field conditions.

Foxtail millet (Setaria italica (L.) Beauv.) is a soft-stemmed summer cereal crop that is grown at a high crop density; however, stem lodging is recognised as a serious yield-limiting factor. The stem-breaking strength of the third to fifth basal internodes has previously been identified as the most important factor in determining the lodging resistance of foxtail millet. We measured variation in stem-breaking strength, length and weight of these internodes at different developmental stages and in response to different crop densities by using foxtail millet cultivars that differed in lodging resistance. The stem-breaking strength of the third internode was greater than of the fourth and fifth internodes, which had comparable stem-breaking strengths; this result was independent of genotype and developmental stage. The stem-breaking strengths of the three internodes were significantly correlated with each other and linearly related across different developmental stages and crop densities. The stem-breaking strength of the three internodes at hard dough stage (Zadoks growth stage Z87, at 30 days after flowering) was less than at other developmental stages in the lodging-resistant genotypes. Stem-breaking strength for the three internodes was correlated with fresh weight (FW) and dry weight (DW) per cm. The variation of FW and DW per cm of the internodes in response to crop density was attributed to the change of FW and DW of the corresponding internodes, rather than to variation in their length. Results from this study showed that the fourth or fifth basal internode was more prone to lodging than the third basal internode because of their lesser stem-breaking strength. Crop density linearly influenced the stem-breaking strength of the three basal internodes. Reducing crop density enhanced stem-breaking strength of third to fifth internodes, which may reduce the risk of stem lodging in this crop. Based on the findings, the stem-breaking strength of the fourth or fifth basal internode measured at the late grain-filling stage from Z77 (late milk) to Z87 (hard dough) differentiated stem-breaking strength, the most important stem lodging associated parameter, in the foxtail millet genotypes.

Seed weight (SW), measured as mass per seed, significantly affects soybean (Glycine max (L.) Merr.) yield and the quality of soybean-derived food. The objective of the present study was to identify quantitative trait loci (QTLs) and epistatic QTLs associated with SW in soybean across 129 recombinant inbred lines (RILs) derived from a cross between Dongnong 46 (100-seed weight, 20.26 g) and ‘L-100 (4.84 g). Phenotypic data were collected from this population after it was grown in nine environments. A molecular genetic map including 213 simple sequence repeat (SSR) markers was constructed, which distributed in 18 of 20 chromosomes (linkage groups). This map encompassed ∼3623.39 cM, with an average distance of 17.01 cM between markers. Nine QTLs associated with SW were identified. These QTLs explained 1.07–18.43% of the observed phenotypic variation in the nine different environments, and the phenotypic variation explained by most QTLs was 5–10%. Among these nine QTLs, qSW-3 (Satt192) and qSW-5 (Satt568) explained 2.33–9.96% and 7.26–15.11% of the observed phenotypic variation across eight tested environments, respectively. QTLs qSW-8 (Satt514) and qSW-9 (Satt163) were both identified in six environments and explained 8.99–16.40% and 3.68–18.43% of the observed phenotypic variation, respectively. Nine QTLs had additive and/or additive × environment interaction effects, and the environment-independent QTLs often had higher additive effects. Moreover, nine epistatic pairwise QTLs were identified in different environments. Understanding the existence of additive and epistatic effects of SW QTLs could guide the choice of which reasonable SW QTL to manipulate and could predict the outcomes of assembling a large number of SW QTLs with marker-assisted selection of soybean varieties with desirable SW.

Accurate estimation of crop yield under aeration stress is crucial for field water table management. In this study, the CROPR crop model was improved in two aspects: (i) a new aeration factor, which was related to a drainage index, was proposed and used to represent the condition of soil aeration; and (ii) a multiplicative structure, instead of the original additive structure, was used in the calculation of dry matter accumulation to include the after-effect of aeration stress. Four-year lysimeter experiments on cotton (Gossypium hirsutum L.) growth under aeration stress were conducted from 2008 to 2011 to calibrate and validate both the original and improved CROPR. The results indicated that the improved CROPR performed better than the original CROPR and was suitable for simulating cotton yield under aeration stress. In the calibration, with the improved CROPR, the root-mean-squared error (RMSE) of seed cotton yield was 832.84 kg ha^–1 with a normalised value (NRMSE) of 15.87%, whereas with the original CROPR, the RMSE was 973.03 kg ha^–1 with an NRMSE of 18.55%. In the validation, with the improved CROPR, the RMSE of seed cotton yield was 686.22 kg ha^–1 with an NRMSE of 14.87%; with the original CROPR, the RMSE was 1019.02 kg ha^–1 with an NRMSE of 22.08%.

Many farmers in Australia and in other countries have a choice of crop or livestock production, and many choose a mixture of both, based on risk preference, personal interests, markets, land resources and local climate. Mixed farming can be a risk-spreading strategy, especially in highly variable climates, but the right scales of each enterprise within the mix may be critical to farm profitability.

To investigate expected farm profits, the probability of breaking even, as well as the worst and best case scenarios, we used farm data and APSIM (Agricultural Production Systems Simulator) to simulate the production of a typical, semi-arid, mixed-farm in southern Queensland. Three farming system scenarios were investigated: I, livestock and more intensive cropping; II, current production system of livestock and minimal cropping; and III, livestock only. We found that the expected profits were in the order system I > system III > system II. The key reason for the lower profits of system II was the high overhead cost of capital to continue some cropping, with low annual cropping income. Under the worst case scenario, in years with low rainfall, system I had the greatest downside risk with far greater financial losses. Systems I and III had similar probabilities of breaking even, and higher than system II, which incurs cropping overheads and limited cropping returns. Therefore, system II was less desirable than either system I or III. This case study helps farmers and advisors of semi-arid mixed farming enterprises to be better informed when making decisions at the paddock and whole-farm level, in both the short and long term, with respect to profit and risk. The method used in this paper can be applied to other mixed farms, in Australia and elsewhere.

Greenhouse gas abatement in the agricultural cropping industry can be achieved by employing management practices that sequester soil carbon (C) or minimise nitrous oxide (N₂O) emissions from soils. However, C sequestration stimulates N₂O emissions, making the net greenhouse-gas abatement potential of management practices difficult to predict. We studied land-management practices that have potential to mitigate greenhouse gas emissions by increasing soil C storage and/or decreasing soil N₂O emissions for a diverse range of broadacre grain cropping sites in New South Wales. Carbon sequestration and N₂O emissions were simulated with the Agricultural Production Systems Simulator (APSIM) for a baseline crop-management scenario and alternative scenarios representing management practices for greenhouse gas abatement, for 15 rainfed or irrigated sites. The global warming potential of the scenarios was quantified at 25 and 100 years after commencement of the alternative practices. Soil C and N₂O emissions were predicted to increase with the use of practices that increased organic matter additions to the soil (e.g. adding a summer crop to the rotation). However, in only a few cases did the increase in soil C storage counter the N₂O emissions sufficiently to provide net greenhouse gas abatement. For rainfed sites, inclusion of a summer crop and/or a pasture in the rotation was predicted to provide greenhouse gas abatement after 25 years, whereas after 100 years, only practices that included a summer crop provided abatement for some sites. For irrigated sites after 25 years, practices that reduced N fertiliser rate while retaining stubble were predicted to provide small abatement, and practices that included a summer crop provided abatement for some sites. After 100 years, practices likely to provide abatement included those that reduced N₂O emissions, such as reducing N fertiliser rate. These findings suggest that a few management practices are likely to abate greenhouse gas emissions across New South Wales grain production sites and that these practices differ for irrigated and rainfed sites.