Summary: | Thesis (PhD(Agric) (Agronomy))--University of Stellenbosch, 2007 === A selection of species suitable for cover crop management in the different wine grape
regions is required to enable more producers to apply this environment friendly practice
in a sustainable manner as part of an integrated production strategy. The correct
management practice(s) to be applied to these species over both the short and long
term in a cooler and warmer wine grape region needed clarification.
The effect of seeding date on the dry matter production (DMP) and weed control efficacy
of seven grasses and sixteen legumes, as well as varieties of three of these species,
was determined during 1991 and 1992. The decomposition rate of the mulches was
determined. In the cooler climate of Stellenbosch (33o55'S, 18o52'E), the Medicago
species, subterranean clovers, pink Seradella and three Vicia species did not compete
effectively with the winter weeds if the weekly precipitation from mid-March to mid-May
(autumn) exceeded 18 mm. The two oat species, as well as rye and triticale produced
more than five t/ha of dry matter if the precipitation exceeded 18 mm per week. The
DMP of the above-mentioned species indicated that these species could be considered
for cover crop management in Lutzville (31o35'S, 18o52'E), if full surface irrigation of 18
mm per week could be applied for 10 weeks directly after sowing, followed by 18 mm
fortnightly. Seeding date had a significant effect on DMP in both regions. A highly
significant correlation (r = 0.85, p ≤ 0.0001) existed between the decomposition rate of
the mulches and the initial amount of dry matter present on the soil surface.
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