The extension of life does not appear to be slowing, representing a great achievement for mankind as well as a challenge for ageing populations. As we move towards an increasingly older population we will need to find novel ways for individuals to make the best of the challenges they face, as the likelihood of encountering some form of adversity increases with age. Resilience theories share a common idea that individuals who manage to navigate adversity and maintain high levels of functioning demonstrate resilience. Traditional models of healthy ageing suggest that having a high level of functioning across a number of domains is a requirement. The addition of adversity to the healthy ageing model via resilience makes this concept much more accessible and more amenable to the ageing population. Through asset-based approaches, such as the invoking of individual, social and environmental resources, it is hoped that greater resilience can be fostered at a population level. Interventions aimed at fostering greater resilience may take many forms; however, there is great potential to increase social and environmental resources through public policy interventions.
S U M M A R YInvestigations are reported of root and shoot growth in semi-dwarf and taller winter wheat varieties grown in contrasting soils over three years. Comparisons were made of the distribution with depth of roots, estimated by injecting rubidium-86 into stem bases and counting the content in soil cores. The relative ability to absorb phosphate from different zones was
SUMMARY
The leaching of nitrate‐N under autumn‐sown arable crops was measured using hydro‐logically isolated plots, about 0.24 ha in area, from 1984–1988. Fluxes of water and nitrate moving over the soil surface (surface runoff), at the interface between topsoil and subsoil (interflow), and in the subsoil (drainflow) were monitored in plots with mole‐and‐pipe drain systems (drained plots); surface runoff and interflow only were monitored in ‘undrained’ plots. Half the drained and undrained plots were direct‐drilled, and on the other half seedbeds were prepared by tillage to 200 mm. Tillage increased the total leaching loss of nitrate by 21 % compared with direct drilling in drained plots. About 95% or the nitrate moving from the soil was present in the water intercepted by the subsoil drains in these plots. In undrained plots less water and nitrate were collected in total; more of the nitrate was present in interflow on ploughed plots and in surface runoff in direct‐drilled land.
Losses of nitrate for the whole experiment from 1978‐1988 were analysed. This showed that, between the harvest of one crop and the spring application of fertilizer to the next, loss of nitrate‐N from ploughed land (Lp) was approximated by Lp=22+Fkg N ha−1, where F was the autumn fertilizer‐N applied. After fertilizer was applied in spring, loss of nitrate‐N depended on rainfall such that for 100 mm rainfall about 30% of the fertilizer‐N was lost by leaching. About 18% more nitrate‐N was lost from direct‐drilled land than from ploughed land in spring, but the total loss was generally small compared to that over winter.
The apparent net mineralization of organic‐N was measured in 1988. In autumn and winter there was little effect of tillage treatment (26 and 31 kg N ha−1 on direct drilled and tilled plots respectively). However, over the year 83 kg N ha−1 were mineralized in tilled plots, and 67 kg N ha−1 in direct‐drilled plots.
Five factors governing the leaching of nitrate are assessed and this identified that fertilizer nitrogen application to the seedbed of winter sown crops and the mineralization of nitrogen from the residues of the previous crop are the most significant factors for nitrogen leaching in the UK.
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