Prescott, C. E. 2014. The scientific value of long-term field trials in forest soils and nutrition research: An opportunist's perspective. Can. J. Soil Sci. 94: 255-262. Long-term field trials are essential in allowing accurate prediction of stand responses to silvicultural treatments. Less well appreciated is the added value that long-term field trials afford to science through a variety of means, often not included in the original experimental plan. Long-term field trials provide a platform upon which additional studies can be conducted; for example a suite of alternative silvicultural trials allowed assessment of influences of forest harvesting on rates of litter decomposition. Well-designed, long-term field trials can be re-purposed to address questions not related to the original research; for example, many of the common garden experiments used to discern influences of different tree species on soil were not originally intended for this purpose. Long-term trials may reveal effects on other ecosystem components such as understorey vegetation or soil organisms, which can generate new hypotheses about ecosystem functioning. Finally, including unusual or non-operational treatments can generate insights that would not occur where trials were constrained to current operational practices. Improved accounting of the additional scientific insights afforded by long-term field trials would go some way towards improved accounting of their true value to science.