There are a number of agricultural field experiments producing food crops that are older than 100 years. They demonstrate the sustainability of their cropping system on a particular soil type and within one climatic zone and importantly, under one management. These long-term experiments can be considered successful. But does this success conform to currently acceptable physical, environmental and socioeconomic criteria? What do these long-term experiments contribute to our understanding of these factors and their possible interactions? Do they need to be and can they be modified to make them economically viable? Do the inputs create environmental issues and can these externalities be measured? What are the effects of external pollutants added to soil and what is the risk of them getting into the food chain? What are the risks of soil degradation? While the successful experiments contribute information on these questions there is even more information to be got from the experiments that have failed or had to be modified to make the system productive and sustainable. The large number of existing long-term experiments, including information from those that failed, at Rothamsted allow many aspects of the points raised here to be discussed in detail and this will be the purpose of this presentation.