Abstract

This study was carried out in Botucatu, State of São Paulo, Brazil in order to evaluate the interference periods of weeds on potato crop. The experimental design was a randomized complete blocks, with four replications, and treatments were arranged in two groups: 1) the crop was kept free from weeds through the periods of 7, 14, 21, 28 and 35 days after emergence, after each period weeds were allowed to grow; 2) the crop was kept weedy for the same periods of the first group, and afterwards the crop was kept weed-free besides a control maintained weed free and another maintained in coexistence with the weeds at 98 days (harvest). Urochloa plantaginea, Cyperus esculentus, Raphanus raphanistrum, Sida rhombifolia, and Galinsoga parviflora were the main weeds in the experimental area, being U. plantaginea the weed with the highest dry matter accumulation. Tuber size and yield were affected by interference of weed community. The total period of weed interference was 35, while the period previous of interference was 7; consequently, the critical period of weed interference was from 7 to 35 after crop emergence.

Key words: Competition, Solanum tuberosum, weed periods, weed management.