A.H Jalali - Agricultural and Natural Resources Research Center, Isfahan, Islamic Republic of Iran.

In order to evaluate the impact of crop residues (zero, 25 and 50%) and nitrogen (zero, 125 and 250 kg ha) on weed seed bank and potato yield, two-years research was conducted as a split plot arranged in randomized complete block design in Rozveh Agriculture Research Station, Freidan-Esfahan. Numbers of weed species in seed bank, aboveground, and both seed bank and aboveground were 1, 2 and 8 respectively. Amaranthus retroflexus L. was dominant weed in seed bank in the both years. Weed seed bank was significantly lower in both N rates than control in the both years with no significant difference between the rates. Weeds biomass with increased use of nitrogen fertilizer increased. In 25 and 50 percent of crop residue treatments, weed seed density was greater than control. 125 kg N ha-1 with 25 percent of crop residue treatment produced the highest tuber yield (27850 kg ha-1), although weed biomass was also high in this treatment. The results showed that management of nitrogen fertilizer application and weed control by applying crop residue crops in rotation will change.

Redroot pigweed (Amaranthus retroflexus L.), Seed, Incorporation, Weed biomass