DISCUSSION: STRUCTURE OF AGRICULTURE: THE POLICY ISSUE

Agricultural and Food Policy,

The effect of tyres and a rubber track at high axle loads on soil compaction-Part 2: Multi-axle machine studies

This paper reports on a study of the effect of the passage of multi-axle harvesting machines on the soil physical properties. In particular, it investigates the effect of the rear tyre of a combine harvester on the amount of soil compaction subsequent to the passage of the front tyre/track. The work was conducted in controlled laboratory conditions to determine the effect of a simulated self-propelled combine harvester with a total machine weight of 30–33 t. This was assessed by embedding talcum powder tracer lines in the soil to measure soil displacement and soil density changes. Dry bulk density and penetrometer resistance were also measured. The results showed that the benefit of the rubber track found by Ansorge and Godwin [2007a. The effect of tyres and a rubber track at high axle loads on soil compaction: Part 1: Single Axle Studies. Biosystems Engineering 98 (1), 115–126] was maintained after the additional passage of the rear tyre. After the passage of a track the effect of rear tyre size was insignificant, but the rear tyre size had a significant influence on soil density when following a leading tyre. This was due to a higher strength layer at the soil surface created by the track which was able to withstand the load of the subsequent passes and protect the soil below from further compaction. Results similar to those found for a tracked machine were also achieved by three passes of a 900 mm section width tyre at 5 t load and 0.5 bar inflation pressure. The track results for the 33 t machine were very similar to those of a smaller combine harvester with a total load of 11 t and similar rut width. The study confirmed the benefit of tracks with regard to soil compaction and emphasised the fact that total axle loads and machine weights are less important than how the loads are distributed to the soil

Soil and crop responses following application of biosolids-derived organomineral fertilisers to ryegrass (Lolium perenne L.) grown in pots

Biosolids-derived organomineral fertilisers (OMF) were produced using a novel technique reported in earlier studies. This technique enables addition of N and potash to biosolids granules to form a balanced NPK fertiliser. Two fertiliser products; OMF10 (10:4:4) and OMF15 (15:4:4), were formulated and tested in a glasshouse facility on pot-grown ryegrass in comparison with urea and biosolids granules at N application rates ranging from 0 to 300 kg ha-1. The aim of this research was to contribute to the understanding of nutrients management and dynamics in grass crops fertilised with OMF. The study focused upon dry matter yield (DMY) and crop responses to applied fertiliser, nitrogen use efficiency (NUE) and fertilisers’ effect on soil fertility. Results indicated that ryegrass responds linearly to application of OMF increasing DMY by about 2% to 27% compared with biosolids but to a lesser extent than urea (range: 17% to 55%). NUE was related to the concentration of readily available N in the fertiliser; urea and OMF showed significantly greater (P<0.05) N recoveries than biosolids (26% to 75%, and 19% to 29%, respectively). Total nitrogen in soil and SOM increased (P<0.05) depending on the concentration of organic-N in the fertiliser applied. DMY was lower but more sustained overtime in biosolids-treated pots. OMF application did not result in significant changes in soil extractable-P levels whereas for urea, it decreased significantly while it showed a significant increase in biosolids-treated pots, where soil-P Index changed from 5 to 6. In OMF-treated soil, soil P Index remained close to constant overtime thereby supporting the purpose of the formulations tested

Chemical composition of outdoor airborne particles at urban schools and possible implications for the air quality in classrooms

Vehicle emissions are a significant source of fine particles (Dp < 2.5 µm) in an urban environment. These fine particles have been shown to have detrimental health effects, with children thought to be more susceptible. Vehicle emissions are mainly carbonaceous in nature, and carbonaceous aerosols can be defined as either elemental carbon (EC) or organic carbon (OC). EC is a soot-like material emitted from primary sources while OC fraction is a complex mixture of hundreds of organic compounds from either primary or secondary sources (Cao et al., 2006). Therefore the ratio of OC/EC can aid in the identification of source. The purpose of this paper is to use the concentration of OC and EC in fine particles to determine the levels of vehicle emissions in schools. It is expected that this will improve the understanding of the potential exposure of children in a school environment to vehicle emissions

Resistance to powdery mildew disease in hops (Humulus lupulus L.)

The virulence of eight isolates of Sphaerotheca humuli (DC.) Burr, was examined on nine varieties of hops (Humulus lupulus L.). Genotypes determined for varieties with race specific resistance generally agreed with previous reports. Although major genes for resistance usually conferred immunity from infection the effectiveness of the gene was shown to be reduced at low temperatures, thereby allowing weak sporulation to develop. The leaf blistering response previously considered to be a consequence of Rg gene determined resistance was shown to be unrelated to the expression of this gene. Quantitative microscopical examination of isolate/variety combinations exhibiting race specific resistance revealed that incompatible fungal sporelings were restricted in the early stages of their development. The expression of the Rg, and R^ resistance genes was associated with a reduction in the frequency with which germinated spores formed haustorial initials. Histochemical and ultrastructural studies showed that the hypersensitive reaction(cell death seen as granulation) in response to epidermal cell penetration was a feature common to most interactions involving major genes for resistance. Adjacent palisade mesophyll cells 'frequently also showed signs of reaction which in severe cases resulted in cellular browning. A 1,3—glucan (probably callose) was deposited in the paramural space and lignin-like compounds appeared to accumulate in the walls and cytoplasmic contents of most reacting mesophyll cells. Callose deposition and lignification were also observed in responding epidermal cells. Infection development on partially resistant breeding lines was studied under laboratory, glasshouse and field conditions. Laboratory experiments revealed that partial resistance to S. humuli was expressed as a reduction in the number of fungal colonies established, an increase in the incubation period and reductions in both the extent and intensity of sporulation. Cellular necrosis was less obvious than in race specific resistance. Comparative studies showed that plants severely infected as seedlings in a glasshouse screen were also severely infected when adult in the hop garden. However, in overall terms there was a relatively poor correlation between the levels of sporulation on seedlings and adult plants of partially resistant breeding lines.Open Acces

Legal Complications of Repatriation at the British Museum

The British Museum has been the target of criticism around the world for its failure to repatriate controversial cultural property to their respective countries of origin. In 1753, a private collector left his collection to Great Britain if it agreed to build a public museum and designate a Board of Trustees whose duty was to protect the collection for the public. Statutorily incorporating the collector’s intent, Parliament passed legislation binding the Board of Trustees to abide by certain principles, including preserving the collection and prohibiting disposal of objects, except in very few circumstances. As such, the Museum is administrated through trust and fiduciary duty law, legally binding the Trustees to preserve the Museum’s collection. This paper argues that, despite pressing demands for the Museum to repatriate cultural property, the Board of Trustees is prohibited from repatriation