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From 1979 to 1991, Modern China, a landmark journal of Chinese studies, published a large number of articles in the field of peasant studies. These articles are of two types: studies of peasants in premodern China, which focus on the rural economy, politics, and ideology; and studies on the history of “peasant studies” itself, which focus on the problems, paradigms and directions of the field. Taken together, all these articles reveal the influence of three major approaches to history: the longue durée perspective of the French Annales school, the “bottom-up” approach to lived experience of the British new social history movement, and the time, space, and demography frame of reference of G. William Skinner.

Continuous cropping obstacle is a common problem in agriculture and autotoxicity of allelochemicals plays a major role in this problem of many crops.In field situations,allelochemicals(autotoxins) must accumulate and persist at phytotoxic levels and comes in contact with the target plant.The potential of plant allelopathy includes the combined effects of all allelochemicals released.Peanut(Arachis hypogaea L.) is a kind of oil crop and highly vulnerable to continuous cropping obstacle.In a previous study we showed the autotoxic potential of peanut root exudates.We have isolated and identified a number of compounds from the root exudates of peanut seedlings including long-chain fatty acids.Long-chain fatty acids are suggested as a group of potential allelopathic compounds.The object of this study was to discuss the relationship between the accumulation of fatty acids in field soil and peanut continuous cropping obstacle,and offer some new theoretical bases for the mechanism study of peanut continuous cropping obstacle.We investigated the synergetic effects of three long-chain fatty acids(Tetradecanoic,Hexadecanoic and Octadecanoic acids) in the root exudates of peanut(Arachis hypogaea L.) on peanut plant growth,production and soil enzyme activities.A simulation experiment in pot culture was carried out using the field soil as the growth medium.It was found that their low content(80 mg/kg soil) slightly stimulated the growth and production of peanut(P 0.05),but their high contents(160 mg/kg soil and 240 mg/kg soil) significantly decreased the growth and production(P 0.05).With increasing fatty acid content in the soil,growth of peanut plants was inhibited and the degree of inhibition increased in a dose-dependent manner.At flowering stage when fatty acids were at their highest content(240 mg/kg soil),plant height,shoot fresh weight,root fresh weight and total biomass were reduced by 14.4%,22.0%,30.9% and 23.7%,respectively.When the content of fatty acids was 160 mg/kg soil and 240 mg/kg soil,peanut pod production was significantly decreased by 15.4%(P = 0.021) and 22.4%(P = 0.005),respectively.Chlorophyll content in peanut leaves,root activity,soil enzymes(sucrase,urease and phosphatase) activities were slightly promoted at low content of fatty acids in soil but were suppressed at high conctents(P0.001).At the highest fatty acid content(240 mg/kg soil),leaf chlorophyll content and root activity were reduced by 21.0% and 31.4% at the seedling stage and 22.7% and 33.3% at the flowering stage.At the flowering stage,sucrase,urease and phosphatase activities were reduced by 25.3,25.4 and 26.1%,respectively,by fatty acids at their highest tested content(240 mg/kg soil).Decreases in photosynthates production,nutrients uptake and rhizosphere nutrients availability were one of the possible reasons which could decrease the peanut growth and production.The accumulation of three long-chain fatty acids,tetradecanoic,hexadecanoic and octadecanoic acids,in field soil has close relationship with peanut continuous cropping obstacle.