No abstract

This trial was conducted over a period of ten years on a sandy soil in a Sauvignon blanc/Ramsey vineyard in Lutzville (31°35'S, 18°52'E), situated in the semi-arid Olifants River Valley of the Western Cape. Twenty-three treatments were applied. Eight cover crop species that received the same amount of fertilizer were controlled chemically at the end of August or at the end of November. Two treatments were also applied in which Avena sativa L. v. Saia ('Saia' oats) and Vicia dasycarpa Ten. (grazing vetch) were controlled mechanically during bud break. In addition to these eighteen treatments, two fertiliser application rates were applied to 'Saia' oats and grazing vetch. A mechanically cultivated control in which no cover crop was sown was included in the trial. Secale cereale L v. Henog and Ornithopus sativus L. v. Emena produced, on average, the highest amount of dry matter at the end of August (3.29 t/ha and 3.06 t/ha, respectively) after receiving on average 278 mm of water, of which 172 mm was supplied by means of a micro-sprinkler irrigation system. The average dry matter produced by Medicago truncatula Gaertn. v. Paraggio and 'Saia' oats at the end of August was not significantly lower than that of the firstmentioned two species. Under conditions of this experiment, it seemed that P and K at a concentration of 10 mg/kg and 78 mg/kg, respectively, in the top 300 mm soil layer supplied the needs of grazing vetch. Saia oats performed poorly unless 30 kg P, 30 kg K and 42 kg N were applied during establishment and the early growing phase. All the species, except M. truncatula Gaertn v. Parabinga, produced additional fibre from September to the end of November following a dry winter (rain and irrigation totaling 201 mm), while none produced additional fibre if the water supply was luxurious up to the end of August (rain and irrigation totaling 364 mm). The cover crops did not produce enough seeds to re-establish successfully over a period of five years. It will, however, be possible to reduce the seeding density of grazing vetch (40% after two seasons) and the two M. truncatula varieties (20% after five seasons) if the species were left to ripen their seeds.

The trial was conducted over a period of ten years (1993/94 to 2002/03) on a sandy soil in a Sauvignon blanc/ Ramsey vineyard near Lutzville (31 o 35'S, 18 o 52'E), situated in the semi-arid Olifants River Valley of the Western Cape. Fourteen treatments, consisting of three grain species and four legumes, managed according to two cover crop management practices, were included. One management practice consisted of cover crops which were sown annually and full surface, post-emergence chemical control which was applied before bud break and when the berries reached pea size (BB). The second management practice consisted of cover crops which were sown biennially. Post-emergence chemical control was applied to the vine row before bud break and full surface when the berries reached pea size (AB). From 1999/2000 to 2002/03 the cover crops were sown annually, while the full surface post-emergence control applied at the end of November was advanced to mid-October. Two treatments in which Avena sativa L. v. Saia ('Saia' oats) and Vicia dasycarpa Ten. (grazing vetch) were sown annually, controlled mechanically in the work row and chemically in the vine row from bud break to harvest (MC), were also applied. These treatments were compared to a control, in which no cover crop was sown and MC was applied. A treatment in which no cover crop was sown and BB was applied (weedchem), was also included. During the third growing season of the vines (1994/95), the grapevine shoot mass of the BB treatments of grazing vetch and Medicago truncatula Gaertn. v. Paraggio ('Paraggio' medic) was significantly more than that of the AB and MC treatments, with the exception of Secale cereale L. v. Henog (AB) and grazing vetch (MC). The first harvest (1994/95) from the grapevines in the BB treatments was significantly higher than that of weedchem and the MC treatments. The grape yield of the BB treatments, grazing vetch (AB) and Ornithopus sativus L. v. Emena (pink Seradella) (AB) was significantly more than that of weedchem and the control during the 1997/98 season. The NO 3 -N concentration in the leaf petioles in all the cover crop treatments was, with the exception of the AB treatments of rye, M. truncatula Gaertn. v. Parabinga ('Parabinga' medic) and grazing vetch, significantly higher than that in weedchem and the control, as measured during the 1994/95 season. The NO 3 -N concentration in the leaf petioles of the BB and AB treatment of a species differed significantly. The N concentration in the juice of the cover crop treatments during the 1995/96 season was, with the exception of 'Saia' oats (MC) and 'Parabinga' medic (AB), significantly higher than that of weedchem and the control. During the 1998/99 season, the N concentration of the juice in the BB and AB treatments of grazing vetch and pink Seradella was significantly higher than that of the MC treatments, two rye treatments, weedchem and the AB treatments of the other cover crops. The concentration of Ca in the juice of the cover crop treatments was, with the exception of the pink Ser...

The trial was conducted over a period of ten years (1993/94 to 2002/03) on a sandy soil in a Sauvignon blanc/Ramsey vineyard near Lutzville (31 o 35'S, 18 o 52'E), situated in the semi-arid Olifants River Valley of the Western Cape.Fourteen treatments, consisting of three cereals and four legumes, managed according to two cover crop management practices, were included. One management practice consisted of cover crops which were sown annually. Full surface post-emergence chemical control was applied before bud break and again when the berries reached pea size (BB). The second management practice consisted of cover crops which were sown biennially. Post-emergence chemical control was applied to the vine row before bud break and full surface control was applied when the berries reached pea size (AB). From 1999/2000 to 2002/03 the cover crops were sown annually, while the full surface post-emergence control applied at the end of November (berries at pea size) was advanced to mid-October. Two treatments in which Avena sativa L. v. Saia ('Saia' oats) and Vicia dasycarpa Ten. (grazing vetch) were sown annually, controlled mechanically in the work row and chemically in the vine row from bud break to harvest (MC), were also applied. These treatments were compared to a control, in which no cover crop was sown and MC was applied. A treatment in which no cover crop was sown and BB was applied (weedchem), was also included. After five years (1997/98), the soil organic matter (SOM) in the 0-150 mm soil layer of the BB and AB treatments of grazing vetch was significantly higher than that of the control and weedchem. During March 2003, the SOM content in the 0-600 mm soil layer of grazing vetch (AB), as well as the 0-150 mm soil layer of Ornithopus sativus L. v. Emena (pink Seradella) (AB) and Secale cereale L. v. Henog (rye) (BB), was significantly higher than that of the control and weedchem. The total inorganic N concentration (TiN) of pink Seradella (BB) was the highest in the 0-150 mm soil layer during the full bloom stage of the grapevines in 1995/96 and significantly higher than that of the other treatments in the 150-300 mm soil layer. The TIN measured in the AB treatments of grazing vetch and pink Seradella as measured after the grapevine harvest (1995/96), was significantly higher than that of the control, weedchem and cereal treatments in the 0-300 mm and 0-150 mm soil layers, respectively. The TIN in the 0-150 mm soil layer of the legumes was, with the exception of pink Seradella (BB), significantly higher than that of the control, weedchem and the BB treatments of the cereals during March 2003. The TiN in the 150-300 mm soil layers of the AB treatments of pink Seradella and the two Medicago truncatula Gaertn. varieties, namely, Parabinga and Paraggio, was significantly higher than that of the control, weedchem and the grain treatments. Potassium concentrations in the 0-150 mm soil layer of the two pink Seradella treatments, the AB treatment of rye, Medicago truncatula Gaertn. v. Paraggio and grazing vetch, as well a...

No abstract