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Adulticides applied against mosquitoes can reduce vector populations during times of high arbovirus transmission. However, impacts of these insecticides on pollinators and other non-target organisms are of concern to mosquito control professionals, beekeepers and others. We evaluated mortality of Culex quinquefasciatus and Apis mellifera when caged insects were exposed to low and high label rates of four common adulticides (Aqua-Pursuit™ [permethrin], Duet® [prallethrin + sumithrin], Fyfanon® [malathion] and Scourge® [resmethrin]) at six distances up to 91.4 m from a truck-mounted ultra-low-volume sprayer. Honey bee mortality was both absolutely low (61 m had limited impacts on honey bee mortality while providing effective mosquito control.

The Mississippi River Delta (U.S.A.) is the major agricultural and aquacultural base where many crops and fishes are sensitive to micronutrients (Zn, Cu, Mn). Zinc is a common yield-limiting factor for rice and was reported to increase rice yields grown on some Delta soils. Soil/sediments in fish ponds of the Delta are drained and disposed for improving the conditions of bottoms. Bioavailability of micronutrients in soils is controlled by distribution between solution and solid-phase and further among various solid-phase compounds. The effects of land uses on distribution and bioavailability of micronutrients (Cu, Zn, Mn) in Mississippi River Delta have not been studied. The objectives of this study were to determine effects of land uses on solid-phase distribution of micronutrients (Cu, Zn, Mn) and Fe in selected vertisols of the Mississippi River Delta alluvial plain. Land uses include upland forest, rice fields and short- and long-term of catfish production. Micronutrients Cu and Zn and Fe and Mn in fresh soils were fractionated into seven operationally defined solid-phase components. Iron and Zn were mainly present in the stable residual fraction (60–70% of the total Zn and 50–60% of the total Fe), Mn mainly in labile fractions (70–80% of the total Mn, including soluble plus exchangeable, carbonate bound, Mn oxide bound, and organically bound fractions), and Cu in the potentially labile fractions (40–50% of the total Cu in amorphous and crystalline Fe oxide bound fractions). Partitioning of these elements into solid-phase fractions varied with land uses. Mn, Fe and Zn in catfish pond soils were higher in labile fractions and lower in potential labile fractions than paddy and forest soils. Paddy and forest soils had higher Fe, Mn and Zn in potential labile fractions. Drying caused redistribution of metals in solid-phase components with possibably lower potential bioavailability and mobility. In conclusion, land uses strongly affect micronutrient distribution in solid-phase components in the selected vertisols of the Mississippi River Delat alluvial plain. The results of the present study may be applicable to other river delta areas of the world.

White clover in New Zealand fixes nitrogen equivalent to 4.5 million tonnes of urea annually. Experiments on the tactical use of about 50 kg N ha-1 yr-1 to stimulate grass growth when clovers are less active indicate that it is generally profitable, but much heavier dressings have rarely been shown to pay at current cost/price structures. The significance of biological nitrogen fixation (BNF) cannot be measured solely by dry matter yields as the quality of herbage is influenced by the contribution of clover and affects yields of animal products and health. Our dependence on BNF gives us a relatively low energycost system of pastoral farming because of the high energy cost of producing fertiliser-N and is therefore more sustainable. The heavy use of fertiliser-N suppresses clover growth and N-fixation, increases losses of ammonia and nitrous oxide to the air and nitrate in drainage water. The extra stock carried leads to greater emission of methane. Reliance on clovers may give lower production but lessens damage to the environment. Keywords: biological nitrogen fixation, energy costs, environment, fertiliser nitrogen, pastoral agriculture, sustainability

The fate of phosphorus (P) during pedogenesis is considered with particular emphasis on vertical distribution within the profile. Information is based on P fractionation studies involving a range of soil sequences in New Zealand. Forms of P in soil parent materials are discussed in relation to soil P transformations. Soil chronosequences, developed in contrasting environments, provide useful information on the pedogenetic pathways of soil P. Although less well understood, soil toposequences can be used to elucidate the effects of slope and drainage on soil-forming processes which involve P.

The loss of total and organic phosphorus and the transformations of inorganic phosphorus fractions were investigated in a chrono-toposequence of strongly weathered and leached soils formed from granite. Over 80% of the total phosphorus originally present was lost from the system during the period of soil development studied. Non-occluded and occluded phosphorus showed a regular, and residual phosphorus an irregular, overall decline in absolute profile quantity with increasing soil development (i.e. increasing weathering and leaching). The proportion of non-occluded phosphorus in the profile declined asymptotically whereas residual phosphorus increased conversely to non-occluded phosphorus and ranged from 58% to 72% of total inorganic phosphorus in the most strongly developed profiles. Proportions of occluded phosphorus increased with increasing soil development. The relative rates of decline of the inorganic phosphorus fractions and forms were shown to be in the order: acid-extractable CaP > non-occluded P > occluded P > residual P. The final profile in the sequence is considered to represent a terminal steady-state system in which small losses of phosphorus from the system are balanced by gains of phosphorus from the atmosphere. The nature and extent of the vegetation on the sequence profiles was linked with declining acid-extractable CaP and non-occluded phosphorus contents. The tendency towards a heath-type vegetation on the later profiles of the sequence leads to a decline in many properties associated with the organic cycle, including total soil nitrogen, oxidisable carbon, and cation-exchange capacity. Declines in profile weights of several other soil properties were also observed. These included total soil calcium, magnesium, potassium, aluminium, iron, and profile clay content. In many cases the observed declines followed an asymptotic path. The declines were attributed to the completion of weathering of stones and gravels in the later profiles of the sequence whereupon no fresh minerals enter the pedogenetic process.

A surgical technique was developed to isolate the arterial supply to the periodontal ligament, pulp and gingiva of the canine mandibular 4th premolar, and to measure the pressure and flow therein. This model system was used to study the interaction between tooth loading and periodontal blood flow. Intrusive forces of less than 350 N were found to produce negligible alteration of the measured blood flow, while loads of 1050 N produced a reduction of flow equivalent to an increase in vascular resistance of approximately 10 per cent, with no effect on arterial pressure. The increase in flow on removal of load was greater than the reduction seen on application, suggesting that reactive hyperemia may occur in the periodontal tissues. The phenomenon of periodontal pulsation first studied by Parfitt ( J. dent. Res. 39 , 608–618) in humans, was examined in the dog as a part of the present work. It was found that the pulsation of the canine mandibular 4th premolar was still in evidence under applied loads 230 times that which Parfitt found to obliterate the movement of the human incisor. This may be taken to indicate that the density and architecture of the periodontal vasculature may, in part, be determined by the loads applied to the teeth during function.

Tissue fluid pressures were monitored in the periodontal ligaments of 19 mandibular canine teeth. Resting (no load) pressures were recorded and changes in the pressure which accompanied the application and removal of forces up to 500 g. All parameters were reexamined after the animals were killed by exsanguination. The resting intraperiodontal pressure (IPP) was −1.86 ± 1.00 mmHg (mean ± 95 per cent confidence limits), markedly less than values obtained by other investigators. As these dogs were positioned with their mandibular canines at a higher elevation relative to the rest of the body than other workers have used, this may indicate that the pressure in the ligament is subject to postural variation. The resting IPP was not correlated with systemic blood pressure, and did not change significantly after exsanguination. Trauma to the ligament raised the resting IPP to −0.36 ± 1.93 mmHg. Application of load resulted in an immediate increase in pressure which decayed rapidly (halving-time less than 1 s). Removal of the load produced the inverse pattern, but with a reduced peak pressure and a longer halving-time. Trauma increased the halving-time for the decay of the load-induced pressures to the point that the pressure increases were judged to be sustained rather than transient. The pressure changes produced by the application of forces to the teeth were small compared to the loads applied, suggesting that the free fluids of the periodontal ligament make only a minor contribution to tooth support.