Rainfall is a major driver for dryland wheat yields across Australia. Many authors have covered issues such as rainfall trends in Australia, and much of this information has been reviewed and updated in recent years in relation to the Millennium drought and associated concerns about climate change. However, despite a long history of work relating rainfall to grain yields, there has been no overall historical review of attempts at predictive methods and their reliability. Although many of these attempts have now been abandoned or revised, and science has moved in different directions, a review is useful to identify historical patterns and to recognise recurring themes. This might lead to new science questions and a re-appreciation of older findings. The aim of this study is therefore to review the overall literature on this topic, provide a historical timeline, and summarise the achievements and any remaining research questions.

The early use of climatic data in Australia was to categorise existing and likely areas for production, with production, not surprisingly, being the emphasis. The search for a crop or climatic index was possibly initiated in an attempt to understand or simplify the complex relationships between crops and the environment. No single index has proved universally applicable, but some acceptance of early growing-season rains as an indicator seems common. The development of complex climatic models, and the availability of quality data for agricultural systems models, has allowed further quantification of the relationship between crops and climate, especially on a seasonal basis. There is little doubt that the relationship between the climatic southern oscillation phenomenon and seasonal rainfall patterns in Australia is important, but its absolute definition remains elusive.

From a producer’s perspective, relationships between rainfall at specific (indicator) periods and seasonal or annual rainfall, as appropriate to specific crops, would be useful simple indicators because many farmers already maintain their own rainfall records.

Climate change is affecting wheat production in Northern Europe; in particular, drought and soil warming during anthesis may cause significant yield losses of the crop. In a search for genotypes tolerant to these stresses, the physiological responses of three spring wheat cultivars to increased soil temperature (3°C above normal) (H), drought (D) and their combination (HD) were investigated. The plants were grown in pots in a climate-controlled greenhouse. Stomatal conductance (g_s), photosynthesis (A), leaf water potential (Ψ_l), and relative water content (RWC) were measured during the treatment period. The responses of these variables to soil drying (for both D and HD) were described by a linear–plateau model, indicating the soil water thresholds at which the variables started to decrease in relation to the control plants. The H treatment alone hardly affected the variables, whereas both D and HD had significant effects. The variable most sensitive to soil drying was g_s, followed by A, Ψ_l, and RWC. Among the three cultivars, earlier stomatal closure during drought in Alora could be a good adaptive strategy to conserve soil water for a prolonged drought, but may not be of benefit under intermittent drought conditions. Later stomatal closure and decline in A for Scirocco under HD and D stresses would be a favourable trait to sustain productivity under intermittent drought. A lower soil-water threshold of g_s associated with a later decrease in A for Scirocco implies that the cultivar was less susceptible to HD and D stresses at anthesis.

Understanding the genetic control of agronomic traits is important in designing crop improvement programs. Study was conducted to analyse the genetic control of root length under water stress. A full diallel cross of four spring wheat lines, along with their F₁ progenies was evaluated under –0.82 MPa water stress in a hydroponic culture. Analysis of variance showed highly significant (P < 0.01) difference among the parental lines and their F₁ progenies. Genotypes Santa Elena, Colotana 296–52 and Pato showed comparable longer roots whereas Tincurrin grew significantly (P < 0.05) shorter roots. Genotypes with long roots were found to have more dominant genes than those with shorter roots. Both general and specific combining abilities were highly significant (P < 0.01) indicating the importance of additive and dominant gene effects in the control of root length under water stress. Genotype Santa Elena was found to be the best general combiner whereas the specific cross Santa Elena × Pato was the best hybrid. Moderate narrow-sense heritability (38%) was observed indicating the possibility of improving root length under water stress. The highly significant specific combining ability value (dominant genetic control) suggests that genotypes with more dominant genes should be selected as parents for hybridisation and the hybrid wheat approach might be helpful in improving water stress resistance.

Biochar has been widely proposed as a relatively novel approach to improve soil quality and increase crop productivity, but its underlying mechanisms are not well understood. A large root system in plants is either a constitutive or an inducible trait dependent on the uptake of resources and the production of shoot dry matter. Here a field experiment was conducted to investigate the effects of biochar amendment on the dynamic growth and development of maize (Zea mays L.), both above- and belowground, and to explore the relationship between soil condition, root traits and shoot biomass over two growing seasons on the Loess Plateau in northern China. Biochar was added to a maize field at rates of 0, 10, 20 and 30 t ha^–1 without mulching and at rates of 0 and 20 t ha^–1 with film mulching before sowing the first crop. The application of straw biochar with 30 t ha^–1 decreased soil bulk density by 12% and increased soil total porosity by 13% in the 0–10-cm soil layer 6 months after biochar addition. Biochar amendment increased soil organic carbon, total soil nitrogen, carbon : nitrogen ratio, and available phosphorus and potassium at the end of each growing season. Although, root growth was inhibited at a rate of 30 t ha^–1 in the early stage of the first year, biochar amendment exhibited a positive effect in other stages, resulting in higher root weight density, root length density and root surface-area density. These responses led to higher growth rates, maize biomass, grain yields and uptake of nitrogen, phosphorus and potassium as the rate of biochar addition increased. Film mulching with biochar amendment achieved the greatest root and shoot biomass and grain yield in both crops, despite differences in climate conditions. Biochar aged in the field for 2 years had the same effect on soil properties and crop production, suggesting that the application of straw biochar may be a promising option for increasing productivity in semi-arid farmland.

Intercropping provides opportunity to harness available resources. Thus, maize intercropped with soybean or peanut (groundnut) was tested with 1 : 1, 1 : 2, and 1 : 5 row proportions along with sole plantings of each crop to measure resource capture and resource-use efficiency. Results revealed that sole peanut had 60% higher maize-equivalent yield and 55% better production efficiency, followed by the 1 : 5 row proportion of maize–peanut, over sole maize. Intercropping increased land-use efficiency by 17–53% and land-equivalent coefficient by 0.21–0.56. The relative crowding coefficient was 39% higher with 1 : 2 maize–soybean, whereas the monetary advantage index was the highest (US$107) with the 1 : 5 maize–peanut. Nitrogen (N) and potassium (K) uptakes by maize were 42.9% and 38.2%, respectively, higher with 1 : 5 maize–soybean, whereas phosphorus (P) uptake was 64% higher with 1 : 5 maize–peanut. However, the least amounts of N, P and K were mined overall with 1 : 5 of maize–soybean. Soil moisture content was improved by 24% and solar radiation interception by 37.8% with soybean alone over maize alone, and these parameters increased with higher row proportions of soybean. The energy parameters also improved with the 1 : 5 row proportions of maize–soybean or peanut intercropping. This study provides a basis for efficient resource use by maize–soybean (or peanut) intercropping system.

Avena is a problematic weed of cropping regions of southern Australia and many areas of the world. In 2010, a random survey was conducted across 14 million hectares of the Western Australian grain belt to monitor the change in herbicide resistance levels by comparing resistance frequency results with a survey conducted in 2005. Screening Avena populations with herbicides commonly used to control this weed revealed that 48% of Avena populations displayed resistance to the commonly used acetyl-Co A carboxylase-inhibiting herbicides, which was lower than that found in 2005 (71%). The broad-spectrum herbicides glyphosate and paraquat provided good control of all Avena populations. Resistance to acetolactate synthase-inhibiting herbicides and to flamprop were detected for the first time in Western Australia in this survey. Therefore, a wide range of weed management options that target all phases of the cropping program are needed to sustain these cropping systems in the future.

Drought is a major factor limiting plant growth causing yield reduction in crops; hence the characterisation of drought tolerance and the development of drought-tolerant crop varieties have been a goal of many crop breeding programs. Using the proteomics approach, we compared the differential protein abundance of drought-tolerant and drought-sensitive soybean leaves subjected to mild or severe drought stress. Proteins were extracted and separated using two-dimensional electrophoresis. Those protein spots with significant and more than 2-fold difference in abundance, 174 in total, were further analysed and 102 proteins were positively identified. Around 38.5% of these proteins were related to energy metabolism and photosynthetic functions, followed by those associated with defence response (36.4%) and protein metabolism (25.2%). Severe drought resulted in a greater number of proteins with differential abundance. Genotypes responded differently to drought stress with the tolerant genotype showing a higher capacity for reactive oxygen species scavenging and maintaining energy supply than the sensitive genotype. The sensitive genotype had a greater number of proteins with significant differential abundance than the tolerant genotypes due to drought. The different patterns in protein abundance induced by drought stress may potentially be utilised to screen and select candidate soybean lines with improved drought tolerance.

Soybean mosaic virus (SMV) causes one of the most destructive viral diseases in soybean (Glycine max). The soybean cultivar Dabaima carries the Rsc4 gene for SMV resistance. The genomic region containing Rsc4 was previously localised within a 100-kb region on chromosome 14. The corresponding region contains three complete nucleotide-binding site (NB) and leucine-rich repeat (LRR) type genes and one incomplete gene that is likely non-functional. Quantitative real-time polymerase chain reaction analysis revealed that three candidate genes encoding NB-LRR proteins were differentially expressed in resistant and susceptible lines when the plants were inoculated with SMV strain SC4. To test the involvement of the three candidate genes in Rsc4 mediated resistance, the three genes were silenced using a Bean pod mottle virus (BPMV)-based vector construct. Silencing of three candidate genes attenuated the Rsc4-mediated resistance and induced SMV symptoms in Dabaima plants. Moreover, Rsc4 candidate genes were 78% downregulated when compared with the empty BPMV vector-treated plants. From these results, we concluded that at least one of the three candidate genes encoding NB-LRR proteins is required for Rsc4 resistance to SMV.

The effects of water deficit stress and recovery on growth, photosynthesis, physiological and biochemical parameters were investigated in the cultivated Beta vulgaris and in two Tunisian provenances (Soliman and Enfidha) of its wild relative B. macrocarpa. Seedlings were cultivated for 4 weeks under optimal or limiting water supply (respectively, 100% and 25% of field capacity, FC). After 2 weeks of treatment, a lot of stressed plants were rehydrated to 100% FC. In the Control, B. vulgaris was more productive than B. macrocarpa, whereas Enfidha provenance showed the highest biomass production (1.6- and 3-fold compared with B. vulgaris and Soliman, respectively), under water deficit stress. A partial re-establishment of growth occurred in both species upon recovery at 100% FC. The sensitivity of B. vulgaris and Soliman provenance to drought was associated with the disturbance of leaf water status and the sharp decrease in net CO₂ assimilation (–66% and –82% as compared with the Control, respectively). On the contrary, the better behaviour of Enfidha provenance was related to its better photosynthetic capacity and leaf relative water content, along with a higher accumulation of amino acids (proline, glycine, and glutamine) implied in the osmotic adjustment. Leaf hexose concentration increased significantly under drought stress in both species whereas leaf sucrose concentration declined only in drought-stressed B. vulgaris and Soliman provenance. Leaf glutamate dehydrogenase activity increased under water deficit in both species despite to a higher extent in B. vulgaris. As glutamate dehydrogenase is implied in catabolism of glutamate to oxoglutarate, it might contribute to provide stressed plants with carbon skeletons.

Enfidha provenance of the spontaneous species B. macrocarpa could be used in the marginal arid ecosystems in order to limit the deficit in fodder and to improve the pastoral value of these regions. In addition, this species could serve as a source of genes for genetic improvement to water deficit stress.

Lucerne (Medicago sativa L.) has the potential to be grown widely under water-limiting conditions in the dairy region of northern Victoria and southern New South Wales, Australia, possibly because of its greater water productivity and because irrigation management of lucerne can be more flexible compared with other forage species. A large-scale field experiment was conducted at Tatura in northern Victoria, over 5 years to determine the effects of limiting (deficit) and non-limiting irrigation management on the dry matter (DM) production, water productivity (irrigation and total water productivity) and stand density (or persistence) of lucerne. Nine irrigation treatments were imposed that included full irrigation, partial irrigation and no irrigation in either a single, or over consecutive, irrigation seasons. In the fifth year of the experiment, all plots received the full irrigation treatment to examine plant recovery from the previous irrigation treatments.

In any one year, there was a linear relationship between DM production and total water supply (irrigation plus rainfall plus changes in soil water) such that DM production decreased as the total water supply – due to deficit irrigation – decreased. Over the 5 years, annual DM production ranged from 1.4 to 17.7 t DM ha^–1 with the highest production occurring in plots that received full irrigation. Irrigation water productivity was inversely related to the amount of water used and was higher in the treatments that had only been partially irrigated for that year compared with the treatments that had been fully watered for that year. Total water productivity values were significantly lower only in the treatments that had not been irrigated for that year, and there was little difference between the treatments that were only partially watered during the year and the fully watered treatments (range 9.1–12.2 kg DM ha^–1 mm^–1 for Year 4). There was no significant reduction in plant density or plant persistence in those plots where deficit irrigation had been imposed. However, the high irrigation regime and poor drainage in the fully irrigated border-check plots significantly reduced plant density and allowed weed infestation in the fifth year of the experiment. These results suggest that, although lucerne DM production is directly related to total water use and may be significantly reduced in the irrigation regions of south-eastern Australia in seasons when water is restricted, the lucerne stand is able to fully recover once a full irrigation regime is resumed. This makes lucerne an ideal forage species for situations when water is limiting.

Multi-species pastures have been viewed as a means to increase forage production relative to monocultures through enhanced three-dimensional occupation of the canopy, which will intercept and use the incident radiation more efficiently. For this to occur, increased production of photosynthetically active tissues such as leaves is required. We tested the hypothesis that intercropping of black oats (Avena strigosa Schum.) and annual ryegrass (Lolium multiflorum Lam.) can increase total and leaf forage production compared with their monocultures. Monocultures and mixed pastures of black oat and annual ryegrass were established, and their tiller morphogenetic and structural traits, as well as components of herbage production, were measured throughout the usage period of the pastures. There was no difference between treatments for total growth rate (77.1 kg dry matter (DM) ha^–1 day^–1), but annual ryegrass pastures presented the greatest stem growth rate (38.1 kg DM ha^–1 day^–1). Taking into account only the vegetative phase, the intercropped pasture produced 20% more leaf than the monocultures. There were no differences between species, either in monoculture or intercropped, for phyllochron, final leaf length, leaf elongation duration and leaf elongation rate. The most important modification in morphogenetic variables due to the inter-specific competition was an increase in senescence rate of annual ryegrass leaves. The average specific green leaf weight in the intercropping pastures corresponded to 84.6% and 137.5% of those values observed for black oat and annual ryegrass pastures, respectively. On the other hand, the intercropping pastures presented 43.5% more tillers than the black oat pastures and 17.8% fewer tillers than the annual ryegrass pastures. It is suggested that intercropping black oat and annual ryegrass does not change tiller ontogenetic processes and that the association of their different size and shape in intercropped pastures could increase pasture leaf production over their monocultures.