Weed interference periods in potato crop

The aim of this research was to evaluate different weed control periods and weed coexistence periods in the potato crop 'Atlantic'. The experiment was carried out in Botucatu-SP, Brazil. The experimental design was a randomized complete block with four replications and the treatments consisted of six control periods, with weed free crop After each period the weeds were allowed to grow freely and after six coexistence periods, and after each period, the weeds were eliminated until harvest. The periods were established in 7, 14, 21, 28, 35 and 42 days after tubers were sown, besides a control maintained weed free and another maintained in coexistence with the weeds. Nine families and 15 species were identified. with Bidens pilosa, Galinsoga parviflora, Brachiaria plantaginea, Commelina benghalensis being the most prominent Tuber production results were adjusted to the non-linear regression model: y = 8.907 + (17.722/ [1 +(x/ 16.865)(8.412)]) (R-2 = 0.963*) equation for the control periods and y = 5.728 + (24.789/[1 +(x/ 39.292)(2.247) A (R-2 = 0.947*) equationfor the coexistence periods. Thus, considering a loss of 5% in productivity as acceptable, it was possible to determine that the period previous to interference (PPI) was 20 days; the total period of weed interference (TPWI), was 21 days and the critical period of weed interference (CPWI), was just one day, from 20 to 21 days after tuber planting.