Introduction Conservation tillage systems using sweep plows or field cultivators leave a high percentage of crop residues on the soil surface, which protects the soil from wind and water erosion (Johnson, 1950; Jones and Johnson, 1982; Allen and Fenster, 1986; Johnson et al., 1974). These systems have been successful in semiarid areas because meager rainfall after plowing does not allow weeds t...

Ischaemum rugosum is a competitive weed in direct-seeded rice systems. Developing integrated weed management strategies that promote the suppression of weeds by crop density, cultivar selection, and nutrition requires better understanding of the extent to which rice interferes with the growth of this weed and how it responds to resource limitation due to rice interference. The growth of I. rugo...