MANAGEMENT OF LONG-TERM FIELD EXPERIMENTS

Long-term field experiments play an essential role in understanding the complex interactions of plants, soils, pests, climate and management, and their effects on sustainable crop production. This paper outlines the management problems associated with long-term field studies and highlights design characteristics and management techniques to ameliorate these problems. Management of new long-term studies includes selecting a suitable site, designing the experiment to facilitate statistical analyses and future expansion, collecting data commensurate with the objectives of the experiment, and incorporating nondestructive changes in the experiment as technology and objectives change. All of the old long-term experiments that we studied have experienced various changes during their existence. Technological advances in areas such as plant populations, varieties, and fertilizer sources must be incorporated into long-term experiments to maintain interest and generate useful data. Incidental changes, such as soil erosion, soil and fertility creep between plots, development of soil acidity, build-up of weeds, and weather effects, are an inevitable feature of long-term experiments. These are often management problems that must be reckoned with, but they usually do not violate the long-term integrity or invalidate the results of the experiment. Primary treatments, e.g., tillage method and cropping system, cannot be changed without jeopardizing the long-term status of the experiment. If properly managed, long-term experiments generate unique, interesting, and valuable information that provides not only a link to the past but also insights into agronomic practices for sustainable future crop production.