Chapter 17: economy-because of the decay of urban centers industrial production and trade suffered, but the western Europeans began to trade more during the middle ages because of: Agriculture-with establishment of Frankish kingdom and Carolingians the land of the northern lands, and this led to harder soils and the heavy plows Developed watermills and a horse collar and crop rotation Sustains lords and retainers Local markets and fairs for small scale exchange while peddlers shopped from one settlement to another. Maritime trade flourishes in Mediterranean