Search

Abstract Chickpea is susceptible to water logging and responds to soil aeration. Oxygen deficiency at both a temporal and spatial scale could occur for a subsurface drip irrigated crop, particularly in heavy clay soils. Use of aerated water irrigation (oxygation) to overcome hypoxia in the rhizosphere was evaluated in broad-acre chickpea crops in 2006 and 2007, in a heavy clay soil of central Queensland, Australia. The injection of 12% by volume air into subsurface drip irrigation water (oxygation) to two consecutive broad-acre chickpea crops resulted in a beneficial effect on yield (gains of 27% and 10% for 2006 and 2007, respectively), but the effect of irrigation regimes at deficit and full irrigation (85 and 100% ETc) was not significantly different. Chickpea yield with aerated subsurface drip irrigation was much higher (3.24 and 2.05 t ha-1) compared to the 7-year (2008–2015) national average yield (1.13 t ha-1). The aerated irrigation resulted into significantly higher gross production water use index (GPWUI) and irrigation water use index (IWUI) particularly in the year when the crop was planted early in the season. There was no significant difference in response to either of these water use efficiency (WUE) indicators between irrigation treatments, with the exception of a significantly enhanced IWUI with the 85% ETc in the first season. These results were consistent with those for cotton on the same site, providing further justification for the capital investment required for oxygated subsurface drip irrigation (SDI) system. Highlights • Aerated water for sub-surface drip irrigation improved chickpea yield by 10–27% compared to the control. • Chickpea yields with subsurface drip irrigation were 81–187% higher than the national average of 1.13 t ha-1. • Aerated water irrigation increased gross production water use index and irrigation water use index for chickpea in a Vertosol. [ABSTRACT FROM AUTHOR]

Chickpea is an important crop that needs more reproductive chilling tolerance for better adaptation to Mediterranean climates. Through divergent evolution in environments that avoided winter cold in space and time, chickpea has largely lost both vernalization response and cold tolerance, unlike its wild progenitors. Cicer chilling tolerance screening is typically done in common gardens with reproductive phase <16 °C where flowering is hastened by vernalization and long photoperiod. Surprisingly, preliminary experiments suggested that vernalization may increase chilling tolerance in chickpea, even in accessions without a significant flowering vernalization response To describe the role of vernalization in phenology, growth and partitioning in domestic and wild Cicer in contrasting temperatures. Do vernalization effects on phenology drive changes in partitioning and growth, pertaining only to vernalization-responsive vrn -types in proportion to growing season vernal load? Alternatively, does vernalization acclimate all plants to better cope with low temperatures? Balanced subsets of well-watered wild and domestic Cicer were grown with/without vernalization in contrasting temperature environments (vegetative phase mean: 12.0–21.6 °C) in SW Australia in 2020/2021. Plant phenology, water-use, growth rates and dry matter partitioning were measured throughout the lifecycle. While wild Cicer became increasingly vernalization-responsive as site temperature increased, the opposite occurred in chickpea. Warm environment growth rates were strongly correlated to vernalization response: domestic rates>wild. Unvernalized wild Cicer grew slowly, flowered late, producing large, thin-leafed canopies maintaining high rates of water use, returning low harvest index. Conversely, in cool environments vernalization consistently protected effect all aspects of growth, particularly in chickpea, regardless of flowering vernalization response. Chickpea was less cold tolerant than wild Cicer , with unstable phenology, lower growth rates, more delayed pod set and lower rates of pod production, particularly without vernalization. Vernalization-linked phenology disruption and downstream effects on vegetative/reproductive sources/sinks explain divergent wild and domestic performance in warm-hot, but not cool-cold environments. In the latter, vernalization appears to be acclimating plants to subsequent cold stress, even in the absence of a flowering vernalization response. Specific adaptation to warm/hot and cool/cold environments in domestic and wild Cicer is the consequence of divergent evolution. Nevertheless, both can acclimate to low temperature stress through early exposure, regardless of vernalization response, suggesting that the sowing climate will influence subsequent responses to cold. This is good news for chickpea breeders because the crop is largely grown in environments where a vernalization response is maladaptive and its introduction would lead to late, unstable phenology. • Vernalization impacts plant development differently in contrasting temperatures. • Warm environment growth effects are explained by vernalization-driven phenology. • In cold environments vernalization protects growth through acclimation. • Cold acclimation occurs in both vernalization responsive and unresponsive plants. • Temperatures at sowing will affect subsequent responses to cold. [ABSTRACT FROM AUTHOR]

Winter crops are the backbone of Australian agriculture. This study reports the first comparative analysis of the impact of temperature and water stress on yields of wheat, barley, canola, chickpea and field pea across four major production zones in Australia (North, East, South and West) using the 2009-2013 National Variety Trials (NVT). Developmental windows of 100 °Cd centred at flowering were used to sample rainfall, vapour pressure deficit (VPD), potential evapotranspiration, water supply/demand ratio, average minimum (Tmin) and maximum (Tmax) temperature, number of days below 0 °C and above 30 °C, incident radiation, photothermal quotient (PTQ) and PTQ corrected by VPD. Flowering was estimated for a mid-season cultivar for each trial using a simulation model (APSIM). There was a consistent negative association between Tmax and yields in all crops, from early in the season in the South and after flowering in the West. Our study supports that high temperature in the non-stressful range is associated with yield reduction with crop specific effects. Days exceeding 30 °C were unlikely before flowering; wheat and chickpea were sensitive to temperatures above 30 °C from early and late in grain filling respectively. Chickpea was sensitive to low temperatures from flowering. Canola was overall the most sensitive to water stress. Unequivocally, the interaction between temperature and water stress exhibited strong regional differences. In the West, with Mediterranean rainfall pattern, high Tmin before flowering was associated with higher yields in wheat, barley, canola and chickpea, indicating a role in promoting early growth and water use and reducing evaporation. In the North, crops depend on initial soil moisture, and high yields were associated with lower Tmin, likely slowing growth and early water use and lessening terminal stress. These relationships need direct experimental confirmation to show causality but there is room for large scale studies to uncover seasonal and regional patterns and highlight targets for research, breeding and management options aimed at improving yield under climate change. [ABSTRACT FROM AUTHOR]

To develop higher yielding and better adapted chickpeas, various breeding programs currently use a limited number of multi-location trials as a surrogate for the target population of environments (TPE). These TPEs have, however, not been adequately characterised, resulting in some uncertainty about the true representativeness of these surrogate locations as selection environments. We used the Agricultural Production Systems sIMulator (APSIM) model to characterise the Northern Grains Region of Australia, which is a major TPE of chickpea, for drought and thermal regimes. The model was first evaluated for its ability to simulate phenology, dry matter and yield of three new commercially-relevant chickpea varieties including PBA Boundary, PBA HatTrick and PBA Seamer. The model was then used to simulate dynamic changes in water stress quantified through the supply demand ratio, and yield of the highest yielding genotype PBA Boundary from 1900 to 2014 at 45 locations within the region. Water stress, and maximum, minimum and mean temperature patterns were derived through cluster analysis of respective averages computed for every 100 °Cd from 900 °Cd before flowering, to 900 °Cd after flowering. The Northern Grains Region TPE was characterised by four types of water stress patterns and five types each of maximum, minimum and mean temperatures patterns. Ward’s cluster analysis of the percentile ranks of simulated seasonal yield resulting from agro-climatic variability of the different locations enabled identification of eight unique agro-ecological regions within the TPE. Locations within each agro-ecological region were geographically contiguous and had highly harmonised annual variability in yield compared to locations of other agro-ecological regions. Overall, the identified agro-ecological regions were fairly homogenous with respect to drought and thermal regimes and could be treated as separate sub-TPEs. We argue that selecting locations within an agro-ecological region should assist breeding for locally adapted genotypes. In contrast, selecting locations distributed across agro-ecological regions could improve the broad adaptation of chickpea. [ABSTRACT FROM AUTHOR]

Monitoring soil water use at the plot level is essential for studying the plant's response to drought or irrigation. However, the current soil monitoring system using moisture sensors is impractical. Soil electromagnetic induction (EMI) surveys can be a rapid, convenient, and non-invasive solution for monitoring soil moisture changes at the plot level. This study developed a crop water use monitoring system for the plot level using an EMI instrument that collects measurements at 0, 20, 40, 60, and 80 cm above the ground surface. The EMI data were converted to bulk soil electrical conductivity (σ) to the depth 1.5 m via an inversion technique and correlated with measured volumetric moisture contents. The EMI system was first tested for variation in ambient temperature. Within the temperature range of 25.5–34 °C, the standard deviation varied between 0.84 and 3.45 mS m−1 with coefficient of variations 1.54–9.26%. The system was then tested on a field trial at Narrabri, New South Wales, Australia, to measure the water use of chickpea genotypes grown over a season. The total water use of chickpeas obtained from EMI surveys correlated highly with values obtained from the Neutron Moisture Meter (NMM) (R2 = 0.73). Time-series of water content, as measured by the EMI survey, could differentiate the water use of different genotypes. In conclusion, the EMI survey is an efficient technique for monitoring crop water use. • A rapid and non-invasive solution for monitoring soil moisture uptake by crops. • A plastic buggy system for multi-layered soil EC a measurements and 2-D inversion analysis. • Water use efficiency of 36 chickpea genotypes was quantified. • Time-series soil moisture analysis identify zones of water uptake. [ABSTRACT FROM AUTHOR]

• Ability of isolates to promote plant growth related to sourced soil environment. • PGP traits was associated with soil environments of rhizobacteria isolated. • IAA increased the ability of the bacteria to withstand stresses. • Most isolates without PGP activities were from sites with high soil fertility. Plant growth-promoting rhizobacteria (PGPR) occur naturally in the rhizosphere, but our understanding of the soil and climatic variables that influence the occurrence of beneficial bacteria is poor. Here, we examined the effects of environmental factors on the occurrence of PGPR in the chickpea rhizosphere soils. A total of 743 rhizobacteria were isolated from the chickpea rhizosphere collected from 74 sampling sites across Australia. Results revealed that the ability of isolates to produce indole acetic acid (IAA) and 1-aminocyclopropane-1-carboxylate (ACC) deaminase were positively correlated with the potential of rhizobacteria to promote root growth. The amount of IAA production was positively correlated with soil copper, manganese and zinc concentrations, electric conductivity and the aridity index, but negatively correlated with soil carbon (C), nitrogen (N) and phosphorus (P) in the soils from which the PGPR were isolated. Additionally, the ability of PGPR to tolerate metal ion toxicity and water stress was related to their ability to produce IAA. The potential of isolates to solubilise P was negatively correlated with the C/N ratio, N, P, C and magnesium content of the soils but none of the soil environmental factors was correlated with the ACC deaminase activity of the isolates. In a principal component analysis, these environmental variables explained 53 % of the variation in the ability of the rhizobacteria to produce IAA and ACC deaminase and/or to solubilise P. These findings could be applied to the design of an efficient PGPR development strategy that incorporates ecological traits and plant growth-promoting mechanisms to increase chickpea production. [ABSTRACT FROM AUTHOR]

Abstract: Monocotyledonous and dicotyledonous plant infecting mastreviruses threaten various agricultural systems throughout Africa, Eurasia and Australasia. In Australia three distinct mastrevirus species are known to infect dicotyledonous hosts such as chickpea, bean and tobacco. Amongst 34 new “dicot-infecting” mastrevirus full genome sequences obtained from these hosts we discovered one new species, four new strains, and various variants of previously described mastrevirus species. Besides providing additional support for the hypothesis that evolutionary processes operating during dicot-infecting mastrevirus evolution (such as patterns of pervasive homologous and non-homologous recombination, and strong purifying selection acting on all genes) have mostly mirrored those found in their monocot-infecting counterparts, we find that the Australian dicot-infecting viruses display patterns of phylogeographic clustering reminiscent of those displayed by monocot infecting mastrevirus species such as Panicum streak virus and Maize streak virus. [Copyright &y& Elsevier]

Abstract: Information on the effects of growing cotton (Gossypium hirsutum L.)-based crop rotations on soil quality of dryland Vertisols is sparse. The objective of this study was to quantify the effects of growing cereal and leguminous crops in rotation with dryland cotton on physical and chemical properties of a grey Vertisol near Warra, SE Queensland, Australia. The experimental treatments, selected after consultations with local cotton growers, were continuous cotton (T1), cotton–sorghum (Sorghum bicolor (L.) Moench.) (T2), cotton–wheat (Triticum aestivum L.) double cropped (T3), cotton–chickpea (Cicer arietinum L.) double cropped followed by wheat (T4) and cotton–wheat (T5). From 1993 to 1996 land preparation was by chisel ploughing to about 0.2m followed by two to four cultivations with a Gyral tyne cultivator. Thereafter all crops were sown with zero tillage except for cultivation with a chisel plough to about 0.07–0.1m after cotton picking to control heliothis moth pupae. Soil was sampled from 1996 to 2004 and physical (air-filled porosity of oven-dried soil, an indicator of soil compaction; plastic limit; linear shrinkage; dispersion index) and chemical (pH in 0.01M CaCl2, organic carbon, exchangeable Ca, Mg, K and Na contents) properties measured. Crop rotation affected soil properties only with respect to exchangeable Na content and air-filled porosity. In the surface 0.15m during 2000 and 2001 lowest air-filled porosity occurred with T1 (average of 34.6m3/100m3) and the highest with T3 (average of 38.9m3/100m3). Air-filled porosity decreased in the same depth between 1997 and 1998 from 45.0 to 36.1m3/100m3, presumably due to smearing and compaction caused by shallow cultivation in wet soil. In the subsoil, T1 and T2 frequently had lower air-filled porosity values in comparison with T3, T4 and T5, particularly during the early stages of the experiment, although values under T1 increased subsequently. In general, compaction was less under rotations which included a wheat crop (T3, T4, T5). For example, average air-filled porosity (in m3/100m3) in the 0.15–0.30m depth from 1996 to 1999 was 19.8 with both T1 and T2, and 21.2 with T3, 21.1 with T4 and 21.5 with T5. From 2000 to 2004, average air-filled porosity (in m3/100m3) in the same depth was 21.3 with T1, 19.0 with T2, 19.8 with T3, 20.0 with T4 and 20.5 with T5. The rotation which included chickpea (T4) resulted in the lowest exchangeable Na content, although differences among rotations were small. Where only a cereal crop with a fibrous root system was sown in rotation with cotton (T2, T3, T5) linear shrinkage in the 0.45–0.60m depth was lower than in rotations, which included tap-rooted crops such as chickpea (T4) or continuous cotton (T1). Dispersion index and organic carbon decreased, and plastic limit increased with time. Soil organic carbon stocks decreased at a rate of 1.2Mg/ha/year. Lowest average cotton lint yield occurred with T2 (0.54Mg/ha) and highest wheat yield with T3 (2.8Mg/ha). Rotations which include a wheat crop are more likely to result in better soil structure and cotton lint yield than cotton–sorghum or continuous cotton. [Copyright &y& Elsevier]

Closing the gap between yields currently achieved on farms and those that can potentially be achieved with best practice and current technology (the yield gap) is a key strategy to intensify grain production without expanding cropland. Much research has been done to quantify the yield gap of wheat, maize and rice globally and of wheat, barley, canola, sorghum and pulse crops in Australia. However, crops are grown in rotations (recurring crop sequences) that vary in their cropping intensities and in the diversity of their species. Little is known about yield gaps at the cropping system level, especially in regions where there are many possible combinations of crop types and fallow periods. This prompted us to investigate crop rotations in Australia's subtropical grains region where current crop rotations include winter and summer cropping with cereal, pulse and oilseed crops interspersed with fallow periods ranging from nil to 18 months duration. To determine the system level yield gaps, we simulated the water-limited yield potential of 26 locally practiced crop rotations for over 800 weather stations by up to 3 soil types per station. We captured the impact of climate variability with 30–35 years by 2–7 fields per rotation for each site. We expressed the results in terms of energy, protein and revenue per hectare per year and mapped the results of the optimal rotations over the cropping zone. Surprisingly, a single rotation (sorghum/fallow/mungbean/wheat/fallow/chickpea rotation; with 4 crops in 3 years, balanced between summer and winter crops and between cereal and pulse crops) was optimal for revenue over almost the whole subtropical grain zone. Using revenue as the metric for yield gaps at statistical local area scale we found, over the whole subtropical zone, a mean revenue gap of 970 $/ha/yr. This represents a relative revenue (Revenue% = 100 x (actual revenue/water-limited revenue)) of 34% which is much lower than expected from the 40–60% relative yields achieved by individual crops. We investigated whether growers may select rotations that have lower revenue than the optimal rotation in response to economic factors such as profit and risk. We found that for much of the area the same rotation that optimised revenue also optimised profit. However, for some of the cropping zone, particularly in the south western portion, a different, less intensive and more winter dominant, rotation was most profitable. Similarly, risk averse farmers may choose less productive and profitable rotations with less risk. • This research has produced the first regional-scale maps of cropping systems yield gaps. • Productivity of cropping in Australia's subtropical grain zone is only 34% of its potential. • Profit-risk trade-offs may be responsible for growers choosing less productive rotations. • These maps and trade-off charts may be useful to engage stakeholders about cropping system design. [ABSTRACT FROM AUTHOR]