Average Seasonal Conditions Research Articles

Substantial genetic gains in reducing breech flystrike and in improving productivity traits are achievable in Merino sheep by using index selection

Context The availability of effective indirect rather than direct selection criteria for genetically reducing breech flystrike is crucial for the Australian wool industry, as expression of breech flystrike is routinely suppressed by management interventions to minimise the risks to sheep health, welfare and productivity. Understanding how much genetic gain can be made in reducing breech strike, while also selecting for other key traits is important in choosing breeding objectives, particularly for Merino genetic improvement programs. Aims We predicted genetic gains from within-flock selection to reduce breech flystrike incidence (FS) and improve productivity under a range of scenarios that all used indirect selection criteria in the genetic evaluation of FS. Methods Three breeding objectives were modelled, by adding FS as a trait to the breeding objective for the Dual Purpose Plus (DP+), Fibre Production Plus (FP+) and Merino Production Plus (MP+) indexes available from MERINOSELECT. A large range of economic values were examined for FS, from 0 to –$240/strike.sheep per year in $20 increments. For all scenarios, full records of productivity traits and pedigree information were assumed to be available for use as selection criteria, as well as records of breech wrinkle, dag and breech cover scores. Predictions were conducted for scenarios assuming (a) moderate heritability for FS (b) low heritability for FS, and (c) low heritability for FS, but higher heritability for dag score than assumed for scenarios (a) and (b). Key results After 10 years of selection, under assumption (a) predicted genetic gains in FS ranged from 0, up to maximum reductions of 0.19, 0.21, and 0.20/strike.sheep per year from use of the FP+FS, MP+FS and DP+FS indexes, respectively. Under assumption (b) predictions of genetic gain for FS were considerably lower and ranged from 0 to maximum reductions of 0.04, 0.06 and 0.06/strike.sheep per year based on use of FP+FS, MP+FS and DP+FS indexes, respectively. Under assumption (c), predicted genetic gains in FS were very similar to those under assumption (b). When 70% of the maximum gains in FS studied were targeted, from 70% to 93% of genetic gains in the overall index (excluding FS) were predicted to be retained when FS had moderate heritability, and from 85% to 95% when FS had low heritability. Conclusions and implications There is a practical range of economic values for FS (from –$60 to –$80/strike.sheep per year for MP+FS and DP+FS indexes and –$60 to –$140/strike.sheep per year for a FP+FS index when the heritability of FS is moderate and –$100 to –$200/strike.sheep per year for a MP+FS index and –$140 to –$240/strike.sheep per year for FP+FS and DP+FS indexes when the heritability of FS is low), that could be used in breeding programs to genetically reduce FS, while retaining competitive levels of genetic gains for other important traits. Reduction of FS is achievable to low levels, after 10–20 years of index selection, similar to levels achieved by mulesing (0.01/strike.sheep per year in average seasonal conditions).

Seasonal performance assessment of refrigerants with low GWP as substitutes for R410A in heat pump air conditioning devices

In this study, the effect of the utilization of refrigerants with a low Global Warming Potential (GWP) instead of R410A in air conditioners on seasonal efficiency was evaluated theoretically. In the study, four different alternative refrigerants were used namely, R446A, R447A, R452B and R454B. The GWP values of all of the studied refrigerants were lower than 750. The calculations were made according to the EN 14825 standard. Average seasonal conditions were applied for heating. The results showed that R446A had the lowest heating capacity and electric consumption. R446A required electric energy consumption for extra heating due to its low heating capacity and therefore it had the lowest seasonal coefficient of performance (SCOP) value. The seasonal energy efficiency ratio (SEER) values of the refrigerants were very close to each other and their average was 6.56. R452B had the most suitable with 3.92 SCOP value among the alternative refrigerants.

Summer-growing perennial grasses are a potential new feed source in the low rainfall environment of southern Australia

In the Mallee region of southern Australia, the dry and variable climate results in frequent summer–autumn feed gaps, restricting the profitability of farms that combine livestock and crop enterprises. To assess the suitability of summer-growing perennial grasses to fill such feed gaps, two replicated field experiments comparing the persistence and productivity of several cultivars were conducted at Hopetoun and Karoonda. The data from these experiments also served to validate a C4 grass model, which was then used in a simulation experiment comparing productivity on two different soil types at three locations. Most grass cultivars established well except on sandy, non-wetting soils. At Hopetoun, four of five cultivars persisted over 6 years, demonstrating the tolerance of the selected cultivars to the typical long, dry summers and cold, wet winters of the region. Biomass production showed little difference between cultivars and a strong response to the amount of summer rainfall, ranging from 1500 to 3000 kg ha–1 under average seasonal conditions and peaking at 9000 kg ha–1 in the very wet summer of 2010–2011. Model performance was satisfactory (R2 0.85–0.93, RMSE 476–1673 kg ha–1, depending on the cultivar), in terms of predicting both the magnitude and the timing of biomass production. Simulation outputs indicated that biomass production closely followed seasonal trends in temperature and moisture availability. Grazing potential was highest from early summer to autumn, which coincides with the period of feed shortages and highest marginal value of forage. In areas with warm-season (October–April) rainfall averages of 175 and 225 mm, the grazing of C4 grass pastures on marginal soils would be possible in at least 40% of the years for 2 and 3 months, respectively. It was concluded that summer-growing perennials are a promising option to alleviate feed gaps on mixed crop–livestock farms in areas with at least 150 mm of rainfall from October to April.

Spatial patterns of soil moisture under forest and grass land cover in a suburban area, in Maryland, USA

Knowledge about the effects of changing environmental factors on stability of spatial structure of soil moisture is important in measurement design and spatial and land-atmosphere modeling, but was rarely considered. We examined the effects of soil temperature and moisture on spatial structure of daily soil moisture at 10-cm and 20-cm depth covering forest and grass sampling points (31 and 11, respectively) over 10months with a maximum between-point distance of 130m. For average seasonal conditions, the peak variance (sill) was 4.8–7.5%2, spatial correlation scale was 0–56m, and temporal scale was 5–90days depending upon season, vegetation type and depth. Changes in soil temperature and moisture moderately affected parameters of the spatial structure, the variance (heterogeneity) and correlation length (continuity), and the effects were higher at 10-cm depth compared to 20-cm depth. Increase in soil temperature by 1°C increased the correlation length by about 0.6m only at the upper depth. Heterogeneity of soil moisture was affected by interaction of variability of soil temperature and moisture so that the peak variance changed by as much as 5%2 and 0%2 under changing soil temperature and by 6%2 and 3%2 under changing soil moisture over almost a year at 10-cm and 20-cm depths, respectively. The spatial structure was relatively stable under changing soil temperature and moisture as the correlation length would not change considerably under small (e.g., inter-annual) in contrast to large (inter-seasonal) variations in soil temperature and intra-annual changes in variance were also not high.

Growth, recovery, and yield of dual-purpose canola (Brassica napus) in the medium-rainfall zone of south-eastern Australia

The effect of grazing of vegetative canola (Brassica napus) with sheep on crop growth and yield was investigated in two field experiments (Expts 1 and 2) in 2008 at Wagga Wagga, New South Wales, Australia. The experiments included a range of cultivars, sowing rates, and grazing periods to investigate the influence of these factors on grazing biomass, crop recovery, and grain yield. Three spring canola cultivars (representing triazine-tolerant, conventional, and hybrid types) were used in both experiments and were sown at three sowing rates and grazed by sheep for 7 days in midwinter in Expt 1, while two different grazing periods were compared in Expt 2. Supplementary irrigation was applied to Expt 1 to approximate average growing season conditions, while Expt 2 received no irrigation. Increased sowing rate produced greater early shoot biomass for grazing, but the-triazine tolerant cultivar produced less biomass than the conventional or hybrid cultivars in both experiments. Grazing reduced dry matter and leaf area by >50%, delayed flowering by 4 days on average, and reduced biomass at flowering by 22–52%. However, there was no impact of cultivar or sowing rate on the recovery of biomass and leaf area after grazing. Grazing had no effect on final grain yield under supplementary irrigation in Expt 1, but reduced grain yield under the drier regrowth conditions in Expt 2. The results demonstrate that grazing canola is feasible under average seasonal conditions in a medium-rainfall environment (400–600 mm) without yield penalty, provided the timing and intensity of grazing are matched to available biomass and anticipated seasonal water supply to support grain production. More broadly, we suggest that grain yield reductions from grazing could be avoided if suitable conditions for regrowth (residual dry matter, length of regrowth period, and adequate moisture) can generate biomass levels in excess of a target value of ~5000 kg ha–1 at flowering. This target value represents a biomass level where >90% of photosynthetically active radiation was intercepted in our study, and in other studies represents a biomass level above which there is little further increase in potential yield. Such a target provides a basis for more objective grazing management but awaits further confirmation with experimentation and modelling.

Major components of atmospheric organic aerosol in southern California as determined by hourly measurements of source marker compounds

Abstract. We report the first hourly in-situ measurements of speciated organic aerosol (OA) composition in an urban environment. Field measurements were made in southern California at the University of California–Riverside during the 2005 Study of Organic Aerosol at Riverside (SOAR), which included two separate measurement periods: a summer study (15 July–15 August) and a fall study (31 October–28 November). Hourly measurements of over 300 semivolatile and nonvolatile organic compounds were made using the thermal desorption aerosol gas chromatograph (TAG). Positive matrix factorization (PMF) was performed on a subset of these compounds to identify major components contributing to submicron (i.e., PM1) OA at the site, as measured by an aerosol mass spectrometer (AMS). PMF analysis was performed on an 11-day focus period in each season, representing average seasonal conditions during the summer and a period of urban influence during the fall. As a result of this analysis, we identify multiple types of primary and secondary OA (POA and SOA). Secondary sources contribute substantially to fine OA mass at Riverside, which commonly receives regional air masses that pass through metropolitan Los Angeles during the summer. Four individual summertime SOA components are defined, and when combined, they are estimated to contribute an average 88% of the total fine OA mass during summer afternoons according to PMF results. These sources appear to be mostly from the oxidation of anthropogenic precursor gases, with one SOA component having contributions from oxygenated biogenics. During the fall, three out of four aerosol components that contain SOA are inseparable from covarying primary emissions, and therefore we cannot estimate the fraction of total OA that is secondary in nature during the fall study. Identified primary OA components are attributed to vehicle emissions, food cooking, primary biogenics, and biomass burning aerosol. While a distinction between local and regional vehicle emissions is made, a combination of these two factors accounted for approximately 11% of observed submicron OA during both sampling periods. Food cooking operations contributed ~10% of submicron OA mass during the summer, but was not separable from SOA during the fall due to high covariance of sources. Biomass burning aerosol contributed a larger fraction of fine OA mass during the fall (~11%) than compared to summer (~7%). Primary biogenic aerosol was also identified during the summer, contributing ~1% of the OA, but not during the fall. While the contribution of both local and regional primary vehicle OA accounts for only ~11% of total OA during both seasons, gas-phase vehicle emissions likely create a substantial fraction of the observed SOA as a result of atmospheric processing.

Numerical Modeling of Atoll Island Hydrogeology

We implemented Ayers and Vachers' (1986) inclusive conceptual model for atoll island aquifers in a comprehensive numerical modeling study to evaluate the response of the fresh water lens to selected controlling climatic and geologic variables. Climatic factors include both constant and time-varying recharge rates, with particular attention paid to the effects of El Niño and the associated drought it brings to the western Pacific. Geologic factors include island width; hydraulic conductivity of the uppermost Holocene-age aquifer, which contains the fresh water lens; the depth to the contact with the underlying, and much more conductive, Pleistocene karst aquifer, which transmits tidal signals to the base of the lens; and the presence or absence of a semiconfining reef flat plate on the ocean side. Sensitivity analyses of steady-steady simulations show that lens thickness is most strongly sensitive to the depth to the Holocene-Pleistocene contact and to the hydraulic conductivity of the Holocene aquifer, respectively. Comparisons between modeling results and published observations of atoll island lens thicknesses suggest a hydraulic conductivity of approximately 50 m/d for leeward islands and approximately 400 m/d for windward islands. Results of transient simulations show that lens thickness fluctuations during average seasonal conditions and El Niño events are quite sensitive to island width, recharge rate, and hydraulic conductivity of the Holocene aquifer. In general, the depletion of the lens during drought conditions is most drastic for small, windward islands. Simulation results suggest that recovery from a 6-month drought requires about 1.5 years.

Response of subterranean clover, balansa clover, and gland clover to lime when grown in mixtures on an acid soil

This study compared the relative tolerances of subterranean clover (Trifolium subterraneum L.), balansa clover (T. michelianum Savi.), and gland clover (T. glanduliferum Boiss.) to acid soil conditions. Seed yield, seedling density, herbage production, N2 fixation, and herbage mineral composition of the 3 legumes were assessed when grown on an acid soil (pHCa of 4.3 and 15% exchangeable Al [0–0.10 m]) with and without the addition of lime (CaCO3). Annual legume species were sown in a mixed sward together with burr medic (Medicago polymorpha L.), and in mixtures with either lucerne (Medicago sativa L.), chicory (Cichorium intybus L.), or phalaris (Phalaris aquatica L.). Due to drier than average seasonal conditions, none of the perennial species persisted beyond the first summer. Lime increased the herbage production of annual legumes by 18–22% and total pasture production by 14% in both 2002 and 2003. Subterranean clover was the most tolerant of the annual legumes to acid soil conditions, showing no visible toxicity symptoms and no response to lime in terms of seed yield. In contrast, both balansa and gland clovers exhibited visual symptoms of manganese toxicity in the absence of lime, with Mn concentrations in the shoots of 817 mg/kg and 626 mg/kg, respectively. Both species responded positively to lime with seed yields increasing by 45% and 124%, respectively. Lime increased the proportion of herbage N derived from N2 fixation by subterranean clover from 29 to 40% and by gland clover from 30 to 43%. Lime had no effect on the proportion of N2 fixed by balansa clover (29–31%), suggesting a suboptimal symbiosis of rhizobia with that species. Adding chicory or phalaris to the pasture mix increased sward herbage production in the establishment year by 39% and 21%, respectively. Based on leaf symptoms and herbage yield responses to lime, Mn toxicity was present in lucerne with tissue levels of up to 916 mg/kg, but no symptoms were observed in chicory (1129 mg/kg) or phalaris (403 mg/kg). Chicory and phalaris were more tolerant of acidity and high levels of Mn than lucerne, gland clover, and balansa clover. The study highlighted the value of the small-seeded annual legumes, balansa clover and gland clover, to the production of mixed pasture swards even in drier than average seasonal conditions. Although more sensitive to acid soils than subterranean clover, they set a greater number of seeds and, in the case of balansa clover, a greater weight of seed under moisture stress in the establishment year than the larger seeded subterranean clover.

The first assessment, using a rangeland monitoring system, of change in shrub and tree populations across the arid shrublands of Western Australia

For the first time, a region-wide assessment of vegetation change across the southern shrublands of Western Australia is reported, using information from 965 shrubland sites of the Western Australian Rangeland Monitoring System (WARMS). The majority of sites were installed between December 1993 and November 1999, and were reassessed between July 1999 and November 2005, with an average interval of just over 5 years. Shrub and tree species density, canopy area and species richness remained the same or increased on the majority of sites. The results were similar when considered at a species level, with most species showing an increase in density, canopy area and the number of sites on which they were found. Recruitment of new individuals to the population was commonplace on virtually all sites and for virtually all species. High rates of recruitment, on many sites, were observed for long-lived species such as Acacia aneura Benth., A. papyrocarpa Benth., Eremophila forrestii F.Muell. and Maireana sedifolia (F.Muell.) Paul G.Wilson. Increases in density, i.e. where recruitment was higher than mortality, were observed for many shorter lived species which are known to decrease in response to excessive grazing (i.e. decreaser species) such as Ptilotus obovatus (Gaudich.) F.Muell., Atriplex vesicaria Benth., A. bunburyana F.Muell. and Maireana georgei (Diels) Paul G.Wilson. However, this result should be tempered by the understanding that acute degradation processes may still be occurring, especially within and surrounding drainage lines, which are away from where the WARMS sites are typically located. Grazing was implicated in decreased density on some sites, particularly those which had experienced below average seasonal conditions. On these sites, decreaser species were particularly affected.

Leaf development in relation to infection by Stagonospora nodorum and Septoria tritici in wheat

Disease and phenology were compared in 2 wheat cultivars (Aroona and Spear) differing in disease resistance and maturity, at early (April-May) to late (June) sowing dates in 1991 and 1992. The cultivars had similar rates of leaf development but the longer season cultivar Spear averaged up to one leaf more on the main stem than the midseason cultivar Aroona, depending on sowing date. The extra leaf production which delayed flag leaf emergence on Spear compared to Aroona at early sowings was associated with lower disease levels in 1991. The occurrence of leaf rust may have diminished this advantage in 1992. Resistance to Septoria tritici in Aroona did not affect disease progress compared to Spear. A comparison of disease over a segment of accumulated thermal time revealed that in 1991, under average seasonal conditions, the earliest sowing experienced the most disease. In 1992, above average late spring rainfall occurred and time of sowing had little influence on disease over the same segment of thermal time. We conclude that a cultivar appropriate for early sowing on the south coast should exhibit increasing leaf production in response to early sowing. This can result in a reduction of disease severity on the upper leaves through disease escape.

Productivity of Hereford, highgrade Simmental and Belmont Red beef herds in central Queensland. 2. Liveweight of the breeding herd and progeny up to weaning

Liveweights of Hereford, highgrade Simmental and Belmont Red calves and cows, between calving and weaning, were compared at Brigalow Research Station, Theodore, Queensland. These cattle grazed predominantly improved pastures growing on cleared brigalow country. Over the 4 calf crops, highgrade Simmental calves were heavier (P<0.05) at birth, 50, 126 and 205 (weaning) days of age (41, 83, 166, 220 kg, respectively) than Belmont Red (33, 72, 141, 191 kg) and Hereford (36, 71, 138, 184 kg) calves. Belmont Red calves were significantly heavier (P<0.05) than Hereford calves at 205 days but not at other ages, while Hereford calves were heavier (P<0.05) than Belmont Red at birth. The advantage to highgrade Simmental calves was greatest during above average seasonal conditions and under these conditions Hereford calves were similar to Belmont Red calves. Conversely, under adverse seasonal conditions Belmont Red calves were heavier than Hereford calves. The 4-year average May liveweight of highgrade Simmental cows (519 kg) was heavier (P<0.05) than Belmont Red (481 kg) which was heavier (P<0.05) than Hereford (465 kg). Highgrade Simrnental breeders were always heavier than Hereford and Belmont Red. While these differences varied according to year, highgrade Simmental were always at least 41 kg heavier than Hereford and 17 kg heavier than Belmont Red. Differences between Belmont Red and Hereford were small and not commercially significant during average to above average years, but favoured the Belmont Red by up to 30 kg following below average seasonal conditions. Production of weaner liveweight per breeder was 125, 132 and 155 kg for Hereford, highgrade Simmental and Belmont Red, respectively. These weights represented 27, 25 and 32 kg weaner production respectively per 100 kg breeder liveweight supported.