| dc.description.abstract | Maize is a major food and forage crop in Kenya and planting density and weeding
regime influence yield. The effects of weeding regimes and maize planting density on
maize forage, grain yield and quality were evaluated during the 200112 short rains and
long rains of2002 at Kenya Agricultural Research lnsitute, Muguga in Central Kenya.
Weeding regimes were weed free (WI), weedy (W2), herbicide (W3) and hand
weeding twice (W4). Maize densities were 9 (01) and 18 plants m-2 (02) intercropped
with beans. Maize was thinned at 98 OAE at tasseling stage and assessed for forage
yield and quality. Stover and edible weeds biomass yield and quality were also
assessed. Soil moisture content down the profile, PAR interception, weed density,
maize height and rate of tasseling was determined gradually over the season. Maize
yield and bean biomass was also determined. The collected data was anaJysed using
GENST AT software and their means separated with LSD at P = 0.05.
Percent interception of photosynthetically active radiation (PAR) was significantly
higher in 02 than in OJ before thinning time but was significantly higher in 01 than
in 02 after thinning in both seasons. Interception of PAR was significantly higher in
W2 compared to WI, W3 and W4, which were similar in both experiments. Soil
moisture content was significantly lower in W2 but similar in WI, W3 and W4. 02
had significantly lower soil moisture content than Dl in season two through out the
season. Thinnings biomass was higher where weeds were controlled and least in the
weedy regime in both seasons. Thinnings biomass was significantly higher in 02 than
01 in both seasons and 01 had significantly higher maize grain yield than 02 in both
seasons. Stover biomass was significantly higher in 0 J than 02 in season one but was
similar in season two. Total forage biomass from Dl was same as in D2 in season one
whereas in season two was significantly higher in D2 than Dl. Beans performed
poorly due to low planting density and shading effects due to maize in both seasons.
The tasseling rate was significantly lower in D2 than DI while W2 had significantly
lowest tasseling rate as compared to WI, W3 and W4, which had similar tasseling rate
in both seasons. Maize plants were significantly short in W2 compared to WI, W3
and W4, which were similar. They were also shorter in D2 than in DI in both seasons.
Total weed biomass at 126 DAE was significantly higher in W4 than in W3 and in DI
than in D2 in both seasons. The cattle-edible weed biomass at the end of the two
seasons was at least 55 % of the total. Thinnings had significantly higher digestibility
(76 %) and crude protein (7 %) than stover. Two times hand weeding (W4) was two
to three times more expensive than using herbicide (W3). Weeds competed for light
and water leading to reduced thinnings, stover and grain yield but increased weed
biomass, which was significantly lower than maize biomass in the weeded plots. High
maize density increased intraspecific-competition (of maize in the hills) for water and
light before thinning time (98 DAE) and significantly reduced plant height, tasseling
rate and grain yield. Hand weeding is labour intensive and thus led to increased
expenses than herbicide use. Planting maize at high density significantly increased
forage quality and quantity, and overall light capture especially before thinning, but
reduced weed biomass and grain yield. | en |
