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Laboratory and field
Agricultural Meteorology Elsevier PublishingCompany,Amsterdam-Printed in The Netherlands Editorial L A B O R A T O R Y AND F I E L D One writes most easily and all going well, most usefully, on matters with which there has been close contact and hence continued thinking. Hence these comments concerning interrelationships of field microclimate and controlled climate studies. They are now best developed as closely complementary and each needing the others information for its own full development; if within the one operational group, this is all for the better. At the extremes, the microclimate work has been concerned with the manner in which the weather with all the complexities and exquisite unpredictabilities nature provides interacts with crop vegetation. The controlled climate has been concerned with plants growing in rooms or cabinets with all features of their environment provided "artificially". Both have been developed vigorously and fruitfully in the last 20-25 years. Both have their protagonists, sorm of whom have at times given the impression regarding information from the other side as scarcely respectable. The field microclimate can give quantitative recording and description of the interactions of the crops and their environments as they occur in "real world" situations. It has shown potential for techniques measuring crop water use and growth rate over short hourly terms. In terms of understanding response to varying weather conditions this is a valuable advance over previous procedures. However, when it comes to recording for short intervals (but continuously) over extended periods of time and irrespective of weather changes, the precision and certainty of the results still leave room for improvement. Improvement is needed for them to become efficient tools of prediction to other environments, other seasons and other crops. They give an impression of the complexities of the theory and of the computation procedures still outrunning the precision of the answers. Similarly there are still considerable restrictions on type of site which can be used. The old problem of separating the interactions of a series of interacting and continuously changing variables is still with us. The controlled climate approach offers quantitative measurement of growth and other performance criteria under defined and stable conditions. It further allows factorial studies of interactions of various climate factors, temperature, humidity, light etc. From this should come quantitative prediction of performance to a range of field conditions. Its limitations have been in the ability to set up combinations of conditions which resemble those in the field, whilst controlled and defined. In so many cases its operations have been with installations in which important factors are well away from field levels, e.g., many units lit with fluorescent tubes; or in which several are neither controlled nor known, e.g., light and air humidity in temperature-regulated glasshouses.
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EDITORIAL
In summary, adherents of both studies have definite faith in their own approach. Both have substantial limitations in the information which they can gather. Both are moving rapidly to reduce the major limitations of their techniques. Above all, both must increasingly call on data from the other side if the full end-use potential of their own work is to be realised. The question is how can this be enhanced and accelerated. From experience of operating the two aspects in a research division three features stand out as of particular importance. The first is the development and use of common and comprehensive instrumentation and terms for description of the operating environment of the plant. For example, both should routinely measure features such as air temperature, leaf temperature, vapour pressure deficit, and wind speed past the leaf rather than just one or two which appear most relevant to the immediate work. The second is that the micro-meteorologist break past the limitation to one-hour or one-day runs under selected weather conditions and get the continuing response of the crop to an extended and non-selective pattern of weather conditions. The techniques then become a flexible tool for the agronomist. The third is that due regard be given to the manner in which the conditions in which a plant is grown do frequently change substantially its response to subsequent light, temperature, moisture conditions, etc. Much of the work which has been done in leaf chambers probably suffers for lack of this. These have been developed as an economic intermediary between the two sides, but where quantitative values based on a series of measurements on single leaves are being used to predict crop responses, sizeable uncertainties can be present. The same probably applies to a number of growth cabinet and climate room measurements. The vehicle for the integration and from that development to wider production situations is the crop modelling now being developed for computer programming. However, the complexity to which these do easily grow can easily inhibit people in fields we are discussing getting access to the basic assumptions. Having these basic assumptions and values readily accessible and comprehensible can allow people working in fields we are discussing to judge when new and improved values their work is producing are ready to be put into sectors of a model, and the calibre of the model appropriately improved. Equally, it can facilitate the continued checking of the relative contribution of various sectors to achieving final sensible and accurate answers, and hence ability to eliminate some sectors as redundant. Sector redundancies will vary as measurement data and understanding grows and flexes. Such data and understanding will provide a continuing check by a wide audience on the basis of the simplicity and power of the assumption data fed in, and a continuing restraint on the computer capacity required to handle such models. It is on this basis that the two sides will become close allies. Each will be providing the data support required to bring the potential of the others work to full and proper utilisation in enhanced crop productivity and guidance of the environment. K. J. MITCHELL
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EDITORIAL
In summary, adherents of both studies have definite faith in their own approach. Both have substantial limitations in the information which they can gather. Both are moving rapidly to reduce the major limitations of their techniques. Above all, both must increasingly call on data from the other side if the full end-use potential of their own work is to be realised. The question is how can this be enhanced and accelerated. From experience of operating the two aspects in a research division three features stand out as of particular importance. The first is the development and use of common and comprehensive instrumentation and terms for description of the operating environment of the plant. For example, both should routinely measure features such as air temperature, leaf temperature, vapour pressure deficit, and wind speed past the leaf rather than just one or two which appear most relevant to the immediate work. The second is that the micro-meteorologist break past the limitation to one-hour or one-day runs under selected weather conditions and get the continuing response of the crop to an extended and non-selective pattern of weather conditions. The techniques then become a flexible tool for the agronomist. The third is that due regard be given to the manner in which the conditions in which a plant is grown do frequently change substantially its response to subsequent light, temperature, moisture conditions, etc. Much of the work which has been done in leaf chambers probably suffers for lack of this. These have been developed as an economic intermediary between the two sides, but where quantitative values based on a series of measurements on single leaves are being used to predict crop responses, sizeable uncertainties can be present. The same probably applies to a number of growth cabinet and climate room measurements. The vehicle for the integration and from that development to wider production situations is the crop modelling now being developed for computer programming. However, the complexity to which these do easily grow can easily inhibit people in fields we are discussing getting access to the basic assumptions. Having these basic assumptions and values readily accessible and comprehensible can allow people working in fields we are discussing to judge when new and improved values their work is producing are ready to be put into sectors of a model, and the calibre of the model appropriately improved. Equally, it can facilitate the continued checking of the relative contribution of various sectors to achieving final sensible and accurate answers, and hence ability to eliminate some sectors as redundant. Sector redundancies will vary as measurement data and understanding grows and flexes. Such data and understanding will provide a continuing check by a wide audience on the basis of the simplicity and power of the assumption data fed in, and a continuing restraint on the computer capacity required to handle such models. It is on this basis that the two sides will become close allies. Each will be providing the data support required to bring the potential of the others work to full and proper utilisation in enhanced crop productivity and guidance of the environment. K. J. MITCHELL