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Aerobic rice cultivation offers the potential to reduce irrigated water use. A multitude of challenges, such as cold sterility, drought stress, and labor shortages, limit its adoption in temperate rice-growing regions. Increasing the duration and extent of soil moisture tension between irrigation events has been demonstrated to slow crop development. Delaying panicle initiation (PI) beyond the optimal window can expose rice to cold nighttime temperatures during the cold sensitive early pollen microspore, severely reducing yield. Tools to assist Australian temperate farmers and researchers in the irrigation management of aerobic rice to ensure PI occurs during the optimal window do not yet exist. Using data collected from an aerobic rice experiment conducted in temperate Australia in 2020–2021 and 2021–2022, a predictive model was built to assist in forecasting PI based on the timing of irrigation. Estimation of the area on an hourly basis of the cumulative evapotranspiration with rainfall subtracted from pre-emergent irrigation to PI, defined as the irrigation deficit integral, was used to account for the frequency, duration, and extent of soil moisture deficit between irrigation events. The relationship between the irrigation deficit integral and the number of days from pre-emergent irrigation to PI (R2 = 0.91) was used to build a model to predict PI with a root mean square error of 1.8 days for the validating data set. Furthermore, an example is provided of how the model can be used as a decision support tool to assist researchers and growers to schedule irrigation of aerobic rice to ensure PI occurs in a timely manner. This will increase the likelihood of high-yielding aerobic rice and may enhance the adoption of water-saving rice cultivation. [ABSTRACT FROM AUTHOR]

Declining water availability is pressing rice growers to adopt water-saving irrigation practices such as aerobic rice to maintain profitability per megalitre (ML) of water input. Irrigators require well-defined irrigation thresholds to initiate irrigation to maximise water productivity. Such thresholds do not exist for temperate rice regions. Adopting a strategy that has been reported to succeed in non-temperate environments may fail in temperate climates, and therefore, needs investigation. This study aimed to investigate, in a temperate Australian environment, the effect of increasing soil moisture deficit during the rice vegetative period on crop physiological development, grain yield and water productivity. The study was conducted in a commercial farm using a randomised complete block design in the 2020/21 and 2021/22 growing seasons. Automated gravity surface irrigation technologies were adopted to enable high-frequency irrigation. Extending soil moisture deficit beyond 15 kPa was found to significantly delay panicle initiation by at least 13–14 days, exposing rice to cold temperatures in Year 1 during the cold-sensitive early pollen microspore period. This reduced yield by up to 55% (4.5 t/ha) compared to the 15 kPa treatment that was not impacted by cold sterility. In the absence of cold sterility, irrigated water productivity and total water productivity ranged between 1.02 and 1.61 t/ML, and 0.84 and 0.93 t/ML, respectively. The highest yields (8.1 and 7.5 t/ha) were achieved irrigating at a soil tension of 15 kPa in growing seasons 2020/21 and 2021/22. This research demonstrates that sound water productivity can be achieved with aerobic rice cultivation in temperate climates, providing cold temperatures during early pollen microspore are avoided. The quantification of the delay in crop development caused by increasing soil moisture deficit provides rice farmers greater confidence in determining the irrigation strategy and timing of pre-emergent irrigation in regions at risk of cold sterility. However, due to the high labour demand associated with aerobic rice, the adoption of aerobic rice at a commercial scale in this Australian environment is unlikely without adopting automated irrigation technology. [ABSTRACT FROM AUTHOR]

To test the hypothesis that root growth at depth is a key trait explaining some genotypic differences in drought tolerance in potato (Solanum tuberosum L.), two varieties (Horizon and Maris Piper) differing in drought tolerance were subjected to different irrigation regimes in pots in a glasshouse and in the field under a polytunnel. In the glasshouse, both cultivars showed similar gas exchange, leaf water potential, leaf xylem ABA concentration and shoot biomass independently of whether plants were grown under well watered or water deficit conditions. Under well watered conditions, root growth was three-fold higher in Horizon compared with Maris Piper, 3 weeks after emergence. Water deficit reduced this difference. In the polytunnel, applying 60% or less irrigation volume compared with full irrigation significantly decreased tuber yield in Maris Piper but not in Horizon. This was coincident with the higher root density of Horizon in deep soil layers (> 40 cm), where water content was stable. The results suggest that early vigorous root proliferation may be a useful selection trait for maintaining yield of potato under restricted irrigation or rainfall, because it rapidly secures access to water stored in deep soil layers. Although selecting for vigorous root growth may assist phenotyping screening for drought tolerance, these varieties may require particular environmental or cultural conditions to express root vigour, such as sufficiently deep soils or sufficient water shortly after emergence. [ABSTRACT FROM AUTHOR]

Practical solutions to optimise nitrogen use efficiency within modern surface irrigated cotton systems in Australia may be possible by regulating the frequency of water and reducing the N applied, compared with typical current practises. A two-year study examined the effect of irrigating at three different water deficits that applied a similar total irrigation volume: >−60 kPa (HF), between −80 and −100 kPa (IF) and between −100 and −120 kPa (LF) for a period from initial flowering throughout boll development, in combination with different nitrogen fertiliser rates on the growth, yield, nitrogen use efficiency and lint quality of cotton. It was hypothesised that shorter deficits would increase N uptake, and nitrogen use efficiency compared with longer deficits caused by consistently higher soil water potentials in the root zone. The major effects of irrigation treatment on growth was to increase plant height and number of bolls, delay crop maturity and decrease micronaire. The irrigation strategy according to yield was most consistently optimised over both seasons when soil matric potential was maintained between −80 and −100 kPa (IF treatment). Lint yield was reduced by 9–13% when the irrigation deficit was <−100 kPa. The most efficient fertiliser use varied between the two years but was always lowest in the treatment with the highest deficit. Irrigation deficit did not change nitrogen uptake or internal nitrogen use efficiency. Nitrogen, even at rates substantially lower than typically used commercially, did not affect fibre quality. There was no interaction between irrigation strategy and N fertiliser rate on yield, fibre quality and fertiliser use efficiency. • Irrigation at soil matric potential >−60 kPa delayed maturity and reduced micronaire. • Intermediate frequency of irrigation produced optimum lint yield and fibre quality. • Low frequency of irrigation advanced maturity up to 10 days but decreased lint yield. • Reduced fertiliser N rate with intermediate frequency of irrigation optimised NUE. [ABSTRACT FROM AUTHOR]

• Grapevine performance of Vertical (VSP) and West-leaned (WSP) canopies was compared. • Potted WSP vines increased morning transpiration without daily differences with VSP. • In the field, West canopy inclination increased leaf area by 13% and yield by 12%. • Water use efficiency did not statistically increase in WSP. • Canopy inclination had minor effects on berry composition. This study tested the possibility of improving whole-canopy water use efficiency (WUE) of grapevines (cv. Bobal) by maximizing radiation interception during the mornings and limiting this during the afternoons, when the vapour pressure deficit and the evaporative demand are higher. The three-year study consisted of two trials conducted in parallel on North-South row oriented potted- and field-grown grapevines. In both trials, performance in terms of vine water use, yield and WUE in a vertical shoot positioned (VSP) system was compared with that of vines leaned 30° towards West (WSP). Potted vines were fully irrigated, whereas field-grown vines were submitted to rain-fed and deficit irrigation conditions. In potted plants, there was no difference in daily transpiration between vines from the WSP and VSP treatments, but transpiration in the mornings was higher in WSP vines. Dry matter and berry size increased in WSP compared to VSP vines. In the field, watering regime had a greater effect than canopy inclination on vine performance. Nonetheless, the WSP system increased leaf area by 13%, yield by 12% and WUE by 11% compared to VSP, although differences in WUE were not statistically significant and the effect on yield was negligible under rain-fed conditions. In both trials, the WSP system did not have a major effect on grape composition (soluble solids, pH, total acidity, concentrations of anthocyanins and polyphenols). In conclusion, this pioneering three-year study proved that leaning vine canopies to the West increased grapevine performance despite the great effect that environmental conditions exerted each year on the data obtained. Further research is required to study the effects of different patterns of light interception on carbon balance and grape biochemical composition. [ABSTRACT FROM AUTHOR]