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Dr. David Powlson, Head of Soil Science Department at AACR-Rothamsted, England, was e-mail interviewed by Dr. Noorallah Juma in 2001 Dr. David Powlson is the Head of Soil Science Department at AACR-Rothamsted. Members of the Department undertake research on a wide range of soil-related topics including nutrient dynamics, soil protection and remediation, soil microbial ecology and issues at the interface between agriculture and the wider environment. Dr. Powlson's personal research interests include: the nitrogen cycle, the nature and turnover of organic carbon in soil using techniques such as NMR spectroscopy, long-term experiments and the opportunities for sequestering carbon in soil organic matter. He is the Past-President of the British Society of Soil Science and a Visiting Professor at the Universities of Reading, Newcastle and Nottingham. [NJ] Dr. Powlson, you are currently the Head of the Agriculture and Environment Division at Rothamsted Research. Could you please tell me how has Soil Science evolved during your tenure at Rothamsted? [DP] There has been a change from purely production agriculture towards environmental aspects. For example in the 1970s we had a large multidisciplinary program of research to identify factors limiting yields of crops such as wheat, looking for ways to reach ever higher yields. This included links to a farmers group called the "Ten Tonne Club" made up of farmers who achieved wheat grain yields of 10 tonne/ha. Since then we have become more concerned with the environmental consequences of growing crops. We are still concerned with obtaining high yields of crops, but not at any cost. Thus we have research on nitrate, phosphate and pesticide leaching and on greenhouse gas emissions from agriculture. We are also much interested in crop quality, e.g. metals entering the food chain. Also in how agriculture fits into the overall landscape and interacts with semi-natural areas. In the UK (and most of Europe) we have very little truly natural areas - agriculture and other lands are in very close proximity. This is rather different from North America. We have also developed research on clean-up procedures for soils that have become polluted from industrial activity.
[NJ] You have also been the president of the British Society of Soil Science. Could you give us some examples of teaching and/or research innovations in UK? [DP] A significant change in soil science teaching and research in Universities in the UK has resulted from changes in the structure of Departments. There are now very few (one or two) Departments of Soil Science. Most now form parts of lager Departments or Schools. This has both negative and positive aspects. It probably means that fewer graduates specializing in Soil Science are being trained than, say, 20 years ago and this is a definite problem. However it also means that more undergraduates and graduate students receive some at least some teaching on soils, often as part of courses in environmental science, biology or geography. In teaching something that seems more common now is to have, within courses, lectures by external scientists or practitioners. I feel this is a useful addition to courses as it shows students how soil science concepts are used in industry, regulatory bodies or in wider aspects of research. Of course, such input has to be in addition to good regular teaching on the basics: it is not a substitute. [NJ] In your opinion, what are the critical issues facing Soil Science today? [DP] There are real risks of damaging soils through misuse. Threats come from inappropriate agricultural practices, direct pollution from industrial activity and from the results of diffuse pollution such as emissions of toxic materials into the atmosphere and their later deposition onto the soil. Although much lip-service is paid to "soil protection", I fear that in reality it is protected much less than water and perhaps air. But tackling these issues are not at all easy. Virtually all human activities (e.g., building homes, manufacturing the various goods our societies require, driving a motor car) have some impact on soils, either directly or indirectly. I think that in a future world of 8-10 billion people it will be impossible to eliminate all adverse impacts. Apart from relatively small wilderness areas and nature reserves, most soils either have to be used in some way (agriculture, building, water catchment, recreation) or are inevitably impacted through atmospheric deposition. A major challenge is to understand soil functions so that they can be protected whilst being realistic about the need for agriculture and other activities. It is totally unrealistic to believe that most soils can be retained in pristine condition - very few are now. Most of our soils need to be used in some way to serve the needs of humanity. But we need to understand how soils function, and what aspects are most fragile, so that management practices and policies can be developed to maintain these functions whilst also meeting our needs.
[NJ] Human population is increasing but the amount of arable land per person is decreasing. How do we solve the problem of producing food, fuel, fibre and feed at a regional as well as a global scale? [DP] I see no alternative to the intensification of agriculture in the areas of the world where production is now low and there are shortages of food, fuel or fiber. I know it is unfashionable to speak of intensification - in areas such as Europe and parts of North America there is scope to de-intensify to some extent, whilst still achieving sufficient production. This would have environmental benefits and could lead to ways of managing our land surface to produce food and other primary products but also deliver environmental services. I have in mind, for instance, using soils in protecting water quality and in modifying greenhouse gas emissions, as well as recreational uses of land. However in other areas this is certainly not an option and I see intensification of agriculture as the only way forward. However, intensification can be done intelligently. For example, traditional agricultural practices should be analysed and the aspects appropriate for the required level of production used or adapted - I think "good practices" have sometimes been abandoned because newer ways were easier but the consequences were not thought through. There are numerous opportunities for improved cultivation practices, water control and retention, nutrient recycling, use of legumes and animal manures, etc. But it has to be realized that some systems are incapable of delivering the necessary outputs for current populations without inputs of nutrients in fertilizers. Just because there may be some over-use of fertilizers within some parts of European and North American agriculture, this is not a reason to deny the benefits of sensible levels of inputs to those living in the Developing world. I see getting this balance right as a key challenge for soil scientists, working with others having complementary skills.
[NJ] The Rothamsted Experimental Research Plots were established in the 1840's. What is involved in maintaining such plots? [DP] Great attention to detail by farm staff and scientists responsible for them. Also the willingness to make some changes - of course continuity is essential and changes should not be made in the light of changing fashions in agriculture or science. But it is necessary to assess such experiments regularly to ensure that they are scientifically valuable and, in the case of agricultural experiments, that they continue to have some agricultural relevance even if this aspect becomes secondary to their value as a scientific resource. In our funding climate we have found that it is important to use the long-term experiments as part of shorter-term studies of topical relevance. For example, we have used them for studies nitrate and phosphate leaching, greenhouse gas fluxes, soil carbon dynamics, sulfur nutrition, accumulation of metals and organic pollutants. We have found that having an archive of stored soil and plant samples greatly enhances the value of the experiments. [NJ] What kind of results have been generated from the Rothamsted Plots? [DP] I will just give one example. Studies of nitrogen budgets in our long-term experiments showed that inputs from the atmosphere were much greater than anyone had realized: at least 40 kg N/ha/yr. This was later confirmed by direct measurements of N deposition and it has been found that inputs from gases (mainly ammonia and oxides of nitrogen) are greater than ammonium and nitrate in rainfall. This research was one element leading to the current understanding the N deposition is now one of the most significant environmental impacts on ecosystems. Other example are in the following papers: [NJ] What is the future use and these and other long-tem plots located in other parts of the world? [DP] I regard them as a vital resource for studies of the sustainability of agricultural systems (including both production and environmental aspects). They are also a scientific resource, both for detecting unexpected trends and for testing hypotheses within numerous areas of the soil, plant and environmental sciences . We have recently been using measurements of changes in soil organic carbon content in many long-term experiments to explore the potential for carbon sequestration in soils through changes in agricultural practice or land-use. I am sure that such data will be used for this in many parts of the world. It is also recognized that organic matter content is a key factor determining a range of soil properties, sometimes termed soil quality. Again, long-term experiments are valuable in studying the likely consequences of different land use and management practices on the long-term sustainability of soils. [NJ] It seems that Soil Science has been developed in agricultural faculties, especially in North America. How can the vast knowledge of Soil Science be integrated with other disciplines of Science? Should Soil Science be taught in Faculties of Science? [DP] A knowledge of soils is vitally important for those involved in many aspects of environmental science and environmental protection as well as agriculture. It is also relevant to hydrology, microbiology, surface chemistry to name only a few subjects. I would like to see some soil science taught to quite a wide range of students, not only those interested in agriculture. Links: |
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