Abstract:
A survey of maize-dairy farmers in the Central Kenyan Highlands
showed that thinnings, green stover, dry stover and weeds from
the maize crop respectively comprised 6%, 10%, 8% and 5% of
the total forage. Nevertheless, most weed research of maize
completely ignores the use of maize crop residues as forage. The
value of weeds from the maize crop is similarly ignored in
assessing the costs and benefits of weed control. The effects of
maize weeding regimes on maize forage and grain yields were
therefore evaluated over three growing seasons in a bimodal
rainfall area (Kiambu). Weeding regimes were weed free (W1),
weedy (W2), pre-emergence herbicide (W3) and hand weeding
twice (W4). Edible weeds had a dry matter digestibility of 65% and
20% crude protein (CP) – higher than in the maize stover (62 and
4%, respectively). The weedy regime (W2) reduced maize forage
quality: the CP was lower in maize stover and thinnings. Although
weeds provided a measurable source of forage for resource poor
farmers, they directly reduced grain yields and the quality and
quantity of maize forage. Long-term costs and benefits were also
evaluated. During the third season (short rains 2002/3), effects of
applying the weeding regimes for the two previous seasons were
quantified by weed emergence and hand weeding times. The
weedy regime (W2) needed 81 man-days ha-1 for weeding,
significantly more than W1, W3 and W4 (67, 63 and 63 man-days
ha-1, respectively). Failure to control weeds thus meant that more
labour was needed to hand-weed subsequent crops.
