Abstract:
Light and water are among essential resources required for production of photosynthates in plants. A study on the
effects of weeding regimes and maize planting density on light and water use was conducted during the 2001/2
short and 2002 long rain seasons at Muguga in - the central highlands of Kenya. Weeding regimes were: weed
free (W1), weedy (W2), herbicide (W3) and hand weeding twice (W4). Maize planting densities were 9 (D1) and
18 plants m-2
(D2) intercropped with Phaseolus vulgaris (beans). The experiment was laid as randomized
complete block design replicated four times and repeated twice. All plots were thinned to 4 plants m-2
at tasseling
stage (96 DAE) and thinnings quantified as forage. Soil moisture content (SMC), photosynthetically active
radiation (PAR) interception, evapo-transpiration (ET crop), water use efficiency (WUE), and harvest index (HI),
were determined. Percent PAR was higher in D2 than in D1 before thinning but higher in D1 than in D2 after
thinning in both seasons. PAR interception was highest in W2 but similar in W1, W3 and W4 in both seasons.
SMC was significantly lower in W2 but similar in W1, W3 and W4. D2 had lower SMC than D1 in season two.
Weeding regime significantly influenced ET crop, while planting density and weeding regime significantly
influenced WUE and HI. D2 maximizes water and light use for forage production but results to increased
intra-specific plant competition for water and light severely before thinning (96 DAE) that reduce grain yield in
dual purpose maize, relative to D1.
