Abstract:
Identical randomized-block experiments were carried out on the effects of
weed competition on weed growth, the temperature, moisture and nutrient content of
soil, and maize performance in 1997 and 1998. The treatments were a weedy check,
weeding once at 3 weeks after sowing (WAS), weeding once at 7 WAS, weeding
twice at 3 and 7 WAS, weeding thrice at 3, 7 and 10 WAS, and a post-emergence
application of atrazine 480F at 3.0 kg a.i/ha.
The weedy check and weeding once at 7 WAS treatments generally enhanced
the growth of weeds which was least when either atrazine herbicide was applied or
weeding occurred thrice at 3, 7, and lOW AS.
Both the mean temperature and moisture of soil at 5cm depth during the course
of the experiments were not affected by the various weed growths which arose from
the treatments. The presence of weeds during maize cultivation as in the weedy
check and weeding once at 7 WAS did not adversely affect soil nutrient content at
maize harvest compared to the weed-free plots in both years. A relatively low
nutrient content in the atrazine-treated soil in 1998 was attributed to a probable loss of
organic matter through erosion of the exposed soil.
Weeding thrice at 3, 7 and lOW AS enhanced the growth and yield of maize
most followed by weeding twice at 3 and 7 WAS and atrazine application
respectively. Maize performance was decreased most by the weedy check followed
by the weeding once at 7 WAS and 3 WAS respectively.
Weed removal generally enhanced the nutrient content of ear leaf at maize
harvest compared to the weedy check. Leaf N was increased by up to 3.4 % in 1997
when weed competition was reduced with either weeding thrice at 3, 7 and 10 WAS
or atrazine application.
