01791naa a2200241 a 450000100080000000500110000800800410001910000150006024500880007526000090016352010320017265300300120465300380123465300310127265300250130365300250132865300330135365300220138665300200140870000160142870000240144477300810146810227042002-12-12       1999    bl uuuu     u00u1 u    #d1 aBEDMAR, F.  aDetermination of the critical period of weed control in corn using a thermal basis.  c1999  aField studies were conducted over 3 years in southeast Buenos Aires, Argentina, to determine the critical period fo weed control in maize (Zea mays L.). The treatment consisted of two different periods of weed interference, a critical weed-free period, and a critical time of weed removal. The Gompertz and logistic equations were fitted to relative yields representing the critical weed-free and the critical time of weed removal, respectively. Accumulated thermal units were used to describe each period of weed-free or weed removal. The critical weed-free period and the critical time of weed removal ranged from 222 to 416 and 128 to 261 accumulated thermal units respectively, to prevent yield losses of 2.5%. Weed biomass proved to be inverse t the crop yield for all the years studied. When weeds competed with the crop from emergence, a large increase in weed biomass was achieved 10 days after crop emergence. However, few weed seedling emerged and prospered after the 5-6 leaf maize stage (10-20 days after emergence)  aAccumulated thermal units  aInterferencia de plantas daninhas  aManejo de plantas daninhas  aNonlinear regression  aRegressao nao-linear  aUnidades termicas acumuladas  aWeed interference  aWeed management1 aMANETTI, P.1 aMONTERUBBIANESI, G.  tPesquisa Agropecuaria Brasileira, Brasiliagv.34, n.2, p.187-193, fev. 1999.