Response of maize (Zea Mays L.) cultivars to single weeding methods at different crop developmental stages

It has been reported that 50 to 95% of small-scale maize (Zea mays L.) farmers
weed their fields once during the growing season. The weeding is done at either 2-3
leaf or 7-8 leaf time of weeding. Farmers using hoes dig up the weeds, shake off the
soil and either leave the weeds to dry in the field or heap them on the side. A field
experiment to evaluate response of 3 maize cultivars weeded to single weeding methods at two different times of weeding was conducted at University of Zambia in
2000/2001. Two controls (no weeding and clean weeding) were used. The cultiv-ars
were MMV400 (open pollinated), SC 601 (single cross) and MM 604 (3- way cross). A
split -split plot design with time of weeding as main plot, weeding method as sub-plot and cultivar as sub-sub plot was used. Standard agronomic practices were employed.
Measurements were taken for growth and development parameters of both the crop and
weeds. Parameters evaluated for the crop included Leaf Area Index (LAI). Leaf Area
Ratio (LAR), and Leaf Weight Ratio (LWR), Stem Weight ratio (SWR), Specific Leaf
Weight (SLW), Root Weight Ratio (RWR), cover and biomass. For weeds parameters
included cover, density and biomass. Visual data was arcsine transformed while nonvisual
was log transformed.
The results indicated that there was no significant differences in the effect of the
two single weeding methods on LAI, LAR, LWR SWR, grain yield and stalk barrenness. Observed differences were between clean weeding (CW) and no weeding(NW) with highest values in LAI (2.13) and lower SWR (0.43) while no weeding had lowest LAI (1.33) and highest SWR (0.46). Grain yield under CW was highest at had 3744 kg /ha while NW had the lowest 1548 kg /ha. Time of the weeding exerted significant effects. The weed cover of 2-3 leaf time of weeding was higher (63.1%)than 7-8 leaf time of weeding (50.7%). Among the cultivars SC 601 showed superior qualities in LAI (1.89), with lower LAR (0.24) and LWR (0.17) and higher SWR(0.46), which exerted negative effects on weed growth. The cultivar MM 604 had relatively similar attributes to SC 601. The highest grain yield was 2956 kg/ha for SC 601. This was followed by MM604 with 2585 kg/ha and MMV 400 with 1966 kg /ha. It
can be concluded that among the cultivars evaluated SC 601 responded with the highest
growth qualities that suppressed weed growth resulting into the highest grain yield and related components at single weeding methods at different times of weeding. MM 604 was closer to SC 601 in all attributes and ranked second. However, MMV 400 responded with the least growth qualities and as such resulted into the least grain and related yield components .