This review summarises reported observations of the effects of waterlogging on agricultural production in Australia and briefly discusses potential remediation strategies. Inconsistencies are demonstrated in the current indicators used for assessment of waterlogging potential across agricultural landscapes as well as in parameters measured in waterlogging studies. It is suggested that predictions of waterlogging potential for landscapes should be based on a minimum dataset that includes pedological, topographical, and climate data for the defined area, as well as observations of plant morphological appearance and visible surface water. The review also summarises the effects of low oxygen concentration in soil on rhizosphere processes, and discusses evidence for direct effects on plant physiology of reductions in soil oxygen caused by waterlogging. Finally, the review describes current crop growth, water use, and yield simulation models used in Australia (SWAGMAN, DRAINMOD, and APSIM) that incorporate waterlogging stress. It is suggested that there is scope for modifications to these models based on recent improved understanding of plant physiological responses to waterlogging and on further research. The review concludes that improvements in modelling waterlogging outcomes to assist growth and yield predictions should ultimately enhance management capacity for growers.

Break-crops such as legumes and oilseeds increase the yield of subsequent cereal crops by reducing the level of diseases and weeds that build in continuous cereal crops, and can also improve water and nitrogen supply. Although the term ‘break-crop’ originates from their role in breaking disease cycles of soil-borne diseases such as take-all (caused by Gaeumannomyces graminis var. tritici), the contribution of take-all control to the overall break-crop effect has not been separated in most studies. We re-analysed a range of medium- and short-term crop-sequencing experiments comprising 18 year × site combinations in diverse environments in southern Australia. An analysis using linear mixed effects models was conducted to: (i) define the agro-environments that lead to increases in take-all incidence in continuous wheat crop sequences, (ii) quantify the effect of take-all on wheat yield, and (iii) ascertain the contribution of the reduction in take-all following break-crops to the size of the total break-crop effect on wheat crop yield. Break-crop effects on wheat yield averaged 0.7 t/ha and ranged from 0 to 2.1 t/ha. On 14 of 18 occasions, take-all contributed to reduced wheat yield in continuous wheat rotations, although the estimated effect exceeded 0.1 t/ha on just six of those occasions. As a result, reduced take-all by break-crops contributed to <20% of the total break-crop effect in all but one instance, where the suppression accounted for 80% of the break-crop effect. In summary, although the break-crops improved wheat yield by 0.7 t/ha, the contribution from take-all control in the 14 locations where it could be quantified was just 0.1 t/ha. Correlation analysis revealed that take-all incidence in wheat was most likely to proliferate in colder, wetter environments. Take-all can severely damage crop yield, and the reduction contributes to the break-crop effect, but the average impact on wheat yield is small and poorly correlated with the potential yield of the wheat crop. The analytical approach helped to quantify the effect of take-all damage on crop yield, to provide further insight into the agro-environment that contributes to high levels of take-all incidence, and to demonstrate that take-all, like many other processes, operates in an episodic manner that is rare but, on occasions, severe.

Pre-harvest sprouting (PHS) in wheat severely reduces yield and end-use quality, resulting in substantial economic losses. The Chinese winter wheat line CA 0431, with white grain, showed high PHS resistance for many years. To identify quantitative trait loci (QTLs) of PHS resistance in this line, 220 F₂ plants and the corresponding F_2 : 3 lines derived from a cross between CA 0431 and the PHS-susceptible cultivar Zhongyou 206 were used for PHS testing and QTL analysis. Field trials were conducted in Beijing during the 2010–11 and 2011–12 cropping seasons, and in Anyang during 2011–12. PHS resistance was evaluated by assessing the sprouting responses of intact spikes. In total, 1444 molecular markers were used to screen the parents, and 31 markers with polymorphisms between the resistant and susceptible bulks were used to genotype the entire F₂ population. Broad-sense heritability of sprouting rate was 0.71 across environments. Inclusive composite interval mapping identified four QTLs, QPhs.caas-2BL, QPhs.caas-3AS.1, QPhs.caas-3AS.2, and QPhs.caas-3AL, each explaining 2.8–27.7% of the phenotypic variance across environments. The QTLs QPhs.caas-3AS.1, QPhs.caas-3AS.2, and QPhs.caas-3AL were located at similar positions to QTLs reported previously, whereas QPhs.caas-2BL is likely a new QTL flanked by markers Xbarc1042 and Xmag3319. Line CA 0431 and the identified markers can be used in breeding programs targeting improvement of PHS resistance for white-kernel wheat.

Maize (Zea mays) grain yield has been described to be particularly susceptible to environmental conditions around silking; however, a better temporal description of the effect of resource deprivation during this period is needed. Additionally, yield progress and the subsequent increase in the demand of assimilates may result in source limitation during the grain-filling period in current hybrids. This work assessed the effect of (i) short (∼5 days) and intense shading stresses imposed at different times, and (ii) thinning during the effective grain-filling period, on yield components of an Argentinean, widespread hybrid. Grain yield was affected by resource availability during an extended period from ∼300 growing degree-days (GDD) before silking to ∼780 GDD after silking (base temperature = 8°C). Kernel number (KN) was reduced by shading treatments imposed within a relatively extended period of ∼700 GDD centred on silking. Within this period, we establish a critical period of ∼30 days around silking (i.e. –200 to 250 GDD after silking), in which KN susceptibility was maximal. The variation in KN during this period of 450 GDD was mainly accounted for by resource availability and not by timing of treatment imposition within this window. A direct relationship between KN and weight per kernel (KW) for shading treatments imposed from 0 to 200 GDD after silking indicated that compensation of KN reduction by KW increase might not be expected when stress occurred immediately after silking. Kernel number and KW presented an inverse relationship when shading took place after 200 GDD after silking. In addition, thinning after the onset of the effective grain-filling period increased KW. The results indicate that, even in the undisturbed crop, KW was limited by source capacity during grain filling. It is suggested that there is a need to reconsider current agronomic practices and breeding strategies, focusing on the source capacity during the grain-filling period.

Lupinus angustifolius L. (narrow-leafed lupin) is an important grain legume crop for the stockfeed industry in Australia. This species does not form cluster roots regardless of phosphorus (P) nutrition. We hypothesise that this species may have adaptive strategies for achieving critical P uptake in low-P environments by altering shoot growth and root architecture and secreting carboxylates from roots. Three wild genotypes of L. angustifolius with contrasting root architecture were selected to investigate the influence of P starvation on root growth and rhizosphere carboxylate exudation and their relationship with P acquisition. Plants were grown in sterilised loamy soil supplied with zero, low (50 μm) or optimal (400 μm) P for 6 weeks. All genotypes showed a significant response in shoot and root development to varying P supply. At P deficit (zero and low P), root systems were smaller and had fewer branches than did roots at optimal P. The amount of total carboxylates in the rhizosphere extracts ranged from 3.4 to 17.3 μmol g^–1 dry root. The total carboxylates comprised primarily citrate (61–78% in various P treatments), followed by malate and acetate. Genotype #085 (large root system with deep lateral roots) exuded the greatest amount of total carboxylates to the rhizosphere for each P treatment, followed by #016 (medium root system with good branched lateral roots) and #044 (small root system with short and sparse lateral roots). All genotypes in the low-P treatment significantly enhanced exudation of carboxylates, whereas no significant increase in carboxylate exudation was observed in the zero-P treatment. Small-rooted genotypes had higher P concentration than the medium- and large-rooted genotypes, although larger plants accumulated higher total P content. Large-rooted genotypes increased shoot P utilisation efficiency in response to P starvation. This study showed that narrow-leafed lupin genotypes differing in root architecture differed in carboxylate exudation and P uptake. Our finding suggested that for L. angustifolius there is a minimum plant P concentration below which carboxylate exudation is not enhanced despite severe P deficiency. The outcomes of this study enhance our understanding of P acquisition strategies in L. angustifolius genotypes, which can be used for the selection of P-efficient genotypes for cropping systems.

Although generally well adapted and productive, the summer-dormant perennial pastures of southern Australia do not provide a year-round, high nutritive value feed base, they fail to respond to summer rainfall, and they are inefficient in using stored soil water, which can contribute to dryland salinity. An experiment was conducted to test the hypothesis that deep-rooted, summer-active perennial pasture species, matched to soil type, can be grown successfully in southern Australia to increase pasture and animal productivity and to provide high quality feed in summer–autumn. Specifically, the experiment compared a traditional perennial ryegrass (Lolium perenne L.) pasture system with two systems based on summer-active species: the triple system with lucerne (Medicago sativa L.) and tall fescue (Lolium arundinaceum (Schreb) Darbysh), and the novel system with chicory (Cichorium intybus L.) and kikuyu (Pennisetum clandestinum Hochst. ex Chiov). The experiment incorporated three livestock systems (two sheep and one cattle) and took into account the three main soil types occurring on the DPI Hamilton research farm.

After 4 years the perennial ryegrass, lucerne, and tall fescue components were all persisting well and providing feed with high nutritive value (all with frequency scores >70% in the last year of the experiment). The chicory and kikuyu pastures declined over the life of the experiment and were contributing little at the end (frequency scores <15% in the final year). Lucerne, tall fescue, and perennial ryegrass cv. Banquet were able to respond to summer rainfall events to provide valuable, high-quality feed at a time when the quality of perennial ryegrass pasture is normally at its lowest; April 2007 crude protein per cent dry matter values were Avalon perennial ryegrass 16.6, Fitzroy perennial ryegrass 15.6, kikuyu 24.2, lucerne 25.8, and tall fescue 20.3 following a 98 mm rainfall event in late January 2007.

This study has shown that the triple and ryegrass systems were persistent and of high nutritive value, with the sown perennial species contributing the majority of the sward dry matter during the growing season.

Climate change is predicted to cause a significant reduction in the productivity of grasslands and the livestock industry across southern Australia. We have used the GRAZPLAN biophysical simulation models to assess a range of pasture management practices as adaptation options under the SRES A2 global change scenario. The modelling analysis spanned four dimensions: space (25 representative locations), time (2030, 2050, 2070, and a historical reference period of 1970–99), livestock enterprises (five), and management (four adaptation options at different levels). Climate projection uncertainty was taken into account by considering climates from four global climate models. The effectiveness of adaptation options varied widely among enterprises and locations, over time, and under the four projected future climates. Increased soil fertility by adding phosphorus and addition of an area of lucerne to the feed-base were predicted to have the greatest effect in recovering from the negative impact of climate change on profitability. In high-rainfall zones in particular, and compared with the historical period, the most profitable option could return the profitability of livestock production systems to historical levels at 68%, 52%, and 32% of the representative locations at 2030, 2050, and 2070, respectively. At 2030, increased soil fertility, adding lucerne to the feed-base, and confinement feeding in summer recovered overall profit fully at 52%, 28%, and 12% of locations. Removing annual legumes in an attempt to preserve ground cover was ineffective as an adaptation to changing climate. For the majority of location × livestock enterprise combinations, there was at least one individual incremental adaptation that could recover the declines in the profitability at 2030, but effectiveness decreased over time after 2030. It is unlikely that the examined single climate change adaptations to the feed-base of southern Australian livestock production systems can return them to profitability in the second half of the century.

Soil salinity and sodicity have long been major constraints to increasing crop production in many parts of the world. The introduction of salt-tolerant perennial species is one of the most promising alternatives to overcome salinity problems. Cenchrus ciliaris (L.) is a highly drought-tolerant species but there are few available reports on its salt tolerance. The purpose of this work was to assess this trait in two widely used cultivars (Biloela and Texas) and to determine whether cultivation under salinity affected seed germination and plant fitness in the next generation. Trials were performed under field hydroponics conditions. Plants were grown for 5 months in 1000-L PVC boxes containing washed river sand, and were automatically irrigated with a commercial nutrient solution to which NaCl was gradually added to provide to provide average season electrical conductivity (EC) levels of 9, 15, and 19 dS/m. Controls had EC 4 dS/m. Vegetative growth in both cultivars was similarly affected by salinity, and grain yield diminished because of a decreased number of spikelets per plant. Significant growth and yield reductions were registered at EC ∼10 dS/m, and growth continued to decrease with a very small slope as salinity increased, indicating that this species has moderate salt tolerance. Salinity decreased seed germination percentage; however, germination was higher in seeds obtained from plants that had been grown under saline conditions for one season. Growth was similar in plants obtained from seeds that originated from non-salinised and salinised plants. These results suggest that persistence of C. ciliaris in saline soils would not be limited by diminishing plant performance but, rather, by grain yield and seed germination.