Three field experiments in 1998/1999 and 199912000 winter seasons were
carried out at EI·Gimmeza Agricultural Research Station, El-Gharblea Governorate to
estimate yield losses due to weed competition as well as to the role of preceding
winter crops and preceding weed control treatments in wheat on weeds and wheat
productivities. Polynomial regression was carried out to correlate the number and
weight of total weeds/m² to wheat productivities. Results indicate that 50 weedlm² at
one month from sowing decreased number of spikes by 5.4% and wheat production
by 6.7% compared to the weed free treatment. meanwhile, 100 weed specieslm²
decreased number of spikes and wheat productivity by 14.6 and 14.0%, respectivelY2
compared to the weed free treatment. Results showed that one-kilogram of weedsl m
decreased wheat yield by 24.0% compared to the weed free treatment. Preceding
winter crops or preceding weed control treatments can playa role in decreasing weed
population in succeeding wheat where Clover as a forage crop accounted for the
significant reduction in fresh weight of broad-leaved and grassy weeds by 58.7and
39.1%, respectively, and increased wheat grain yield by 156.7% compared to
untreated check. Preceding weed control treatments by isoproturon at rate of 1.25
Ufed. with one hand weeding after 45 days from sowing reduced significantly fresh
weight of annual broad-leaved and grassy weeds by 42.7 and 54.3%, respectively and
increased yield of wheat by 83.0% compared to check. Thus, it is recommend to take
in consideration the role of preceding clover and preceding weed control treatments in
wheat for improving production.