Abstract:
No information is available on the effect of cover crops on weed growth in maize production
in KwaZulu-Natal, South Africa. In a field experiment, the influence of two preceding cover
crops, stooling rye and annual ryegrass, on the growth of maize and the weed Cyperus
esculentus were compared with herbicides and weed control by hoeing. Maize emergence and
early growth were delayed in the presence of physical residues of both cover crop species,
especially in annual ryegrass residues. Growth of C. esculentus was significantly inhibited in
the inter-row maize planting lines by the cover crops for the first 16 days after maize
emergence, but this effect had diminished by day 28. In a pot experiment, the influence of the
same two cover crops on maize and C. esculentus growth was evaluated together with oats
and two additional annual ryegrass cultivars. Here the growth of maize and C. esculentus
growth was suppressed, especially by the root residues of the annual ryegrass, in particular
the cultivar Midmar. Chemical analysis of the leachate of the root residues indicated the
presence of phenolic acids and benzoxazolin-2(3H)-one (BOA). In order to achieve effective
weed control, a weed management strategy combining the mulch retained on the soil surface
with a possible reduction in the type and amount of herbicide(s) should be implemented.
