Abstract:
Field studies were conducted at research field of grain legumes and oil crops research and development
centre at Angunakolapelessa in 2011/12 Maha, 2012 Yala and 2012/13 Maha seasons to evaluate the
effects of mixed weed species on peanut yield. The naturally occurring weeds co-exists in the crop plant
field were allowed to interfere for various intervals to determine the critical weed-free period. Weeds
were broadly categorized into 3 categories grasses, broadleaves and sedges. Two sets of treatments were
maintained in the experiments, first set of treatment consisted of weed free periods [WFP] of 2 (Tl), 4
(T2), 6[T3), 8 (T4), 10 (T5) weeks from planting, total weed free [T6) and full season weedy (T7). The
plots were maintained weed-free until the beginning of the period as treatments, and then weeds were
allowed to germinate and compete until the end of the cropping period. The second set of treatments
consisted of weedy periods (WP) of 2(T8), 4 (T9), 6 (T10), 8 (T il), and 10(T12) weeks from planting
were compared with total weedy and total weed free treatments. The effects of weed existence in various
intervals and weed free periods on peanut yield were investigated. Weed free condition was maintained
by hand-weeding. The crop was maintained according to the recommendations of Department of
Agriculture. The predicted critical period of weed control, in the presence of a mixed population of weeds,
was found to be from 3 to 8 weeks after planting (WAP). Peanut yield decreased as weed interference
intervals increased, demonstrating the need for weed control throughout the growing season in the
presence of mixed weed populations.
