Crop structure in winter oats and the effect of nitrogen on quality-related characters

The relationship between panicle structure and oat grain quality characteristics was examined in a winter oat (Avena sativa) experiment, cv. Gerald, fertilized with 80 and 200 kg/ha N. Spikelets on each whorl were counted and separated into primary, secondary, and tertiary grains, which were counted and weighed, and the kernels extracted manually and weighed. Tiller and whorl rank had relatively small effects on weight per grain and kernel content. Nitrogen application significantly increased weight per primary and secondary grain on the main stem and T1, the first tiller, while spikelet and grain numbers increased only on T1. However, weight per grain and kernel contents in all whorls on both the main stem and T1 were not significantly affected by nitrogen. Although kernel contents were significantly affected by nitrogen application on some occasions, increases and decreases were less than 2.5%. Across the whole plant, numbers of primary and secondary grains increased at the higher nitrogen application, but weight per primary grain and kernel contents were unaffected. However, weight per secondary grain significantly increased at the higher nitrogen application, thus improving uniformity of grain size which is of value to millers.     

Root architecture of sorghum genotypes differing in root angles under different water regimes

Plant root architecture offers the potential for increasing soil water accessibility, particularly under water-limited conditions. The objectives of this study were to evaluate the root architecture in two genotypes of sorghum (Sorghum bicolor (L.) Moench) differing in root angles and to assess the influence of different deficit irrigation regimes on root architecture. The response of two sorghum genotypes, ‘Early Hegari-Sart’ (EH; steep root angle) and ‘Bk7’ (shallow root angle) to four irrigation treatments was investigated in two replicated outdoor studies using large pots. The results indicated that EH possessed steeper brace and crown root angles, fewer brace roots, greater root biomass, and root length density than Bk7 at deeper soil depths (i.e., 15–30 and 30–45 cm) compared with a shallower depth (i.e., 0–15 cm). Across the soil profile, EH had greater root length density and length of roots of small diameter (<1 mm) than Bk7. Accordingly, EH showed more rapid soil-water capture than Bk7. Different levels of irrigation input greatly affected root architecture. Severe deficit irrigation (25% of full crop transpiration throughout the season) increased the angle and number of crown roots, root biomass, and root length density compared with 75 and 100% of full crop transpiration treatments. Consequently, root system architecture can be effectively manipulated through both genotypic selection and irrigation management to ensure optimal performance under different levels of soil available water.     

The Warrumbungle Post‐Fire Recovery Project—raising the profile of soils

The impacts of a wildfire and subsequent rainfall event in 2013 in the Warrumbungle National Park in New South Wales, Australia were examined in a project designed to provide information on post‐fire recovery expectations and options to land managers. A coherent suite of sub‐projects was implemented, including soil mapping, and studies on soil organic carbon (SOC) and nitrogen (N), erosion rates, groundcover recovery and stream responses. It was found that the loss of SOC and N increased with fire severity, with the greatest losses from severely burnt sandstone ridges. Approximately 2.4 million t of SOC and ~74,000 t of N were lost from soil to a depth of 10 cm across the 56,290 ha affected. Soil loss from slopes during the subsequent rainfall event was modelled up to 25 t ha^?1, compared to a long‐term mean annual soil loss of 1.06 t ha^?1 year^?1. Groundcover averages generally increased after the fire until spring 2015, by which time rates of soil loss returned to near pre‐fire levels. Streams were filled with sand to bank full levels after the fire and rainfall. Rainfall events in 2015–2016 shifted creek systems into a major erosive phase, with incision through the post‐fire sandy bedload deposits, an erosive phase likely related to loss of topsoils over much of the catchment. The effectiveness of the research was secured by a close engagement with park managers in issue identification and a communications programme. Management outcomes flowing from the research included installation of erosion control works, redesign of access and monitoring of key mass movement hazard areas.     

Flow alteration and thermal pollution depress modelled growth rates of an iconic riverine fish,the Murray cod Maccullochella peelii

The serial discontinuity concept (SDC) proposes that hypolimnetic‐releasing impoundments cause major disruptions to the naturally occurring physical, chemical and biological gradients of rivers but that this impact diminishes with distance downstream. Such a gradient in discharge, flow velocity and temperature regime occurs below a large hypolimnetic‐releasing impoundment, the Hume Dam, on the River Murray in south‐eastern Australia. To examine the effects of this disturbance gradient on a warm‐water large‐bodied freshwater fish, the Murray cod (Maccullochella peelii), a bioenergetics model was developed and calibrated to explore energy expended under differing water velocities and temperature regimes. Model simulations predicted negative growth of juveniles directly downstream of the impoundment, due largely to the energetic costs associated with active and, to a lesser extent, standard metabolism outweighing the achievable energetic gains through food consumption. As flow velocity and temperature regimes became more favourable downstream, so did the simulated growth of the species. It was not until +239 km downstream of the impoundment that the model predicted that flow velocity and temperature regimes were suitable for greater weight gains. The modelled growth responses of juvenile Murray cod are consistent with the predictions of the SDC, emphasising that changes in the bioenergetics of individuals are likely to be reflected in reduced growth rates under the changed flow velocity and temperature regimes imposed by disturbance gradients. This research represents a valuable step in the biological understanding of Murray cod within variable riverine environments and emphasises the urgency required to mitigate impacts associated with hypolimnetic impoundments.     

Field scale row unit vibration affecting planting quality

Precision Agriculture - With recent developments allowing increased planter speeds, improving spatial uniformity of crop emergence will continue to be an important focus of research. Vertical...     

Development of multiple cutaneous and follicular neoplasms associated with canine papillomavirus type 3 in a dog

A 12‐year‐old spayed English pointer dog developed multiple skin lesions including pigmented viral plaques, basal cell carcinomas, squamous cell carcinomas and trichoblastomas. Canine papillomavirus type 3 was detected in multiple lesions suggesting common aetiology.

     

Modelling optimal timing and frequency of insecticide sprays for knockdown in preparation for other control measures

A modelling investigation was conducted into optimizing the number of sprays and inter-spray interval to reduce an insect population to a low level, for example, prior to pheromone trapping or the release of sterile males. The model population was age-structured and density-dependent. If spray mortality is 100% for each spray, then the ideal spraying schedule is easily determined from the durations of the various life stages. For spray mortality of less than 100%, a simulation was used to determine optimal spraying schedules. Relative length of the larval period, fertility rate and age to first oviposition were found to be the most important biotic parameters for this determination. Their importance is magnified as spray mortality decreases. The stage targeted by sprays and the percent mortality caused by each spray are also important in determining the required number of sprays. Using medfly (Ceratitis capitata Wiedmann) biotic parameters as an example when the spray targets adults, it appeared that neither the stage at which density-dependent mortality takes effect, nor the form of the adult survivorship curve are important in determining the optimal spray schedule.     

Energy Boom and Gloom? Local Effects of Oil and Natural Gas Drilling on Subjective Well‐Being

Prior to the precipitous drop in oil prices in 2014, the U.S. had experienced a substantial increase in oil and natural gas extraction due to technological advancements including horizontal drilling and hydraulic fracturing. This increased energy development likely created both benefits and costs, but the net effects for local residents are not well understood. This paper examines the effects of conventional and horizontal oil and natural gas drilling in Texas on subjective assessments of life‐satisfaction and bad mental health days for nearby residents. Horizontal drilling has statistically significant deleterious effects on well‐being, but the effects are driven by the Dallas‐Fort Worth (DFW) metropolitan area, an area with both very high levels of horizontal drilling and a large urban population.