Bøger i Developments in Plant and Soil serien

The production of rice has increased considerably in recent years due to the release of improved varieties and the adoption of better fertilization practices. Nevertheless, the production and use of inorganic N fertilizer involves costly investments in terms of energy and transport, the need for complex manufacturing plants, as well as the potential for environmental pollution. The use of agricultural systems that include dinitrogen fixing organisms appears to be an economically sound cultural practice. In the particular case of rice, biological nitrogen fixation by Azolla, blue-green algae (BGA), and heterotrophic microorganisms has long been recognized, in southeast Asia, as a fertilizer for rice culture. The Azolla-Anabaena association has the unique property of being able to retain a significant amount of nitrogenase activity in the presence of combined nitrogen, making the system compatible with inorganic nitrogen fertilization. Researchers working with Azolla (N fixation) are dispersed in 2 countries of southeast Asia, Africa, Europe and Latin America, making it difficult to share ideas, concepts and research results on a more personal basis. Considering the potential positive impact of growing rice in association with Azolla, and the lack, to date, of an international gathering of scientists dedicated to Azolla research, the First International Workshop on "Practical Applications of Azolla for Rice Production" was organized by the University of Puerto Rico-Mayaguez Campus.

Soil acidity is a major limitation to crop production in many parts of the world. Plant growth inhibition results from a combination of factors, including aluminum, manganese, and hydrogen ion toxicities and deficiencies of essential elements, particularly calcium, magnesium, phosphorus, and molybdenum. Agricultural management practices and acid precipitation have increased acid inputs into the ecosystem and heightened concern about soil acidity problems. While application of lime has proved to be effective in ameliorating surface soil acidity in many areas, significant soil acidity problems still exist. Scientists from Alberta, Canada, recognized the need to provide a forum for researchers from different disciplines to exchange information and ideas on solving problems of plant growth in acid soils. As a result of their efforts, the First International Symposium on Plant-Soil Interactions at Low pH was held at Grande Prairie, Alberta, Canada, in July 1987. In many acid soil areas, liming materials are not readily available, the cost may be prohibitive, or subsoil acidity cannot be corrected by surface application of lime. New management approaches involving both the plant and the soil are needed in these situations. Progress has been made in the selection and breeding of acid-tolerant plants. However, continued progress will be limited by our lack of understanding of the physiological and biochemical basis of differential acidity tolerance among plants.

Third International Symposium on `Structure and Function of Roots', NITRA, Czechoslovakia, August 3-7, 1987

Nitrogen turnover in the soil-crop system; comparison of fourteen simulation models.- NQuantitative aspects of nitrogen nutrition in crops.- Modelling of the nitrogen cycle in farm land areas.- Nitrate leaching and soil moisture prediction with the LEACHM model.- Nitrate leaching and soil moisture prediction with the LEACHM model.- Some results of nitrogen simulations with the model ANIMO.- The distribution of water and nitrogen in the soil-crop system: a simulation study with validation from a winter wheat field trial.- Modelling water flow, nitrogen transport and root uptake including physical non-equilibrium and optimization of the root water potential.- Modelling water flow, nitrogen transport and root uptake including physical non-equilibrium and optimization of the root water potential.- Simulation of nitrogen dynamics and biomass production in winter wheat using the Danish simulation model DAISY.- Simulation of the nitrogen balance in the soil and a winter wheat crop.- Modelling nitrogen dynamics in a plant-soil system with a simple model for advisory purposes.- Simulation of nitrogen in soil and winter wheat crops: modelling nitrogen turnover through organic matter.- Simulation of nitrogen in soil and winter wheat crops: modelling nitrogen turnover through organic matter.- Simulation of nitrogen in soil and winter wheat crops: a management model that makes the best use of limited information.- Modelling water flow, nitrogen uptake and production for wheat.- WHNSIM - a soil nitrogen simulation model for Southern Germany.- A comparison of the performance of N simulation models in the prediction of Nmin on farmers' fields in the spring.- Response of wheat to nitrogen fertilization, a data set to validate simulation models for nitrogen dynamics in crop and soil.- List of participants.

In the history of the International Plant Nutrition Colloquium from its first meeting in 1954, this meeting, the 13th Colloquium, is the first to be held in Asia and will be the last in the 20th century. The 20th century has seen huge changes in the number and activities of mankind. Our population has increased from around 1. 7 billion to more than 5. 8 billion and technological innovations have completely altered our way of living. As a consequence of such rapid change, we are facing many problems including changes in our environment of a global scale. But, while food shortage has been a serious concern to mankind throughout our history, serious food shortages in the 20th century have been confined to limited times and areas. As Lester Brown discusses in this volume, farmers have increased food production heroically on demand. We, the plant nutritionists should be proud of our support to the world's farmers which has helped them make their achievement possible. During the 20th century, the science of plant nutrition also has achieved great progress as described by Jack Loneragan; it became established as a discipline firmly based in science, defined the chemical elements supporting plant growth, and has contributed to improvements in plant production and environmental quality, as readers will find in many contributions in this volume.