The aim of this study was to assess the effects of crop management practices on the diversity, structure, and composition of weed communities. A total of 30 fields (15 fields each) in low-input and conventional farming systems were surveyed in north-eastern Iran. In the conventional cropping system, both mineral fertilizers and herbicides were applied, while in the low-input cropping system, the fertilizer was mainly manure and herbicides were avoided. The results showed that the pool of species, species richness, number of unique species, and Shannon’s diversity index were greater in the low-input system than in the conventional system. Both cropping systems had more broad-leaved species than grasses and more annual species than perennial species. All the multivariate methods of analysis that were applied revealed that the weed community composition was significantly different between the two management types.The low-input cropping favored herbicide-susceptible broad-leaved weeds, legumes, and weeds with biodiversity value, whereas a high proportion of herbicide-tolerant grasses was found in the conventional fields.The results suggest that low-input cropping can sustain high weed diversity and abundance.

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