Cover Crop Management in a Chardonnay/99 Richter Vineyard in the Coastal Region, South Africa. 2. Effect of Different Cover Crops and Cover Crop Management Practices on Grapevine Performance

The trial was conducted over a period of 10 years (1993/94 to 2002/03) on a medium textured soil in a Chardonnay/99 Richter vineyard near Stellenbosch (33°55’S, 18°52’E), situated in the Coastal Wine Grape Region of the Western Cape. Sixteen treatments, consisting of three grain species and five legumes, managed according to two cover crop management practices, were included. The one cover crop management practice consisted of cover crops being sown annually and full surface post-emergence chemical control being applied before bud break and when the berries reached pea size (BB). The other management practice consisted of cover crops being sown biennially and postemergencechemical control 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-emergencechemical control applied at the end of November was advanced to mid-October. These treatments were compared to a control, in which no cover crop was sown and the weeds were controlled mechanically in the work row and chemically in the vine row from bud break to harvest (approximately the first week of February). A treatment in which no cover crop was sown and full surface post-emergence chemical weed control was applied from before bud break to harvest (weedchem) was also included. During the 1994/95 season, the shoot mass of the two-year-oldgrapevines in the BB treatments was significantly higher than that of the control and the AB treatments. In the following season, the shoot mass and grape yield of the BB treatments was, with the exception of Vicia faba L. v. Fiord (faba bean) and Avena sativa L. v. Overberg, significantly higher than that of the control and weedchem. The grape yield of the control and AB treatments was significantly less than that of weedchem. Although significant differences in shoot mass (2000/01 and 2002/03) and grape yield (2002/03) were detected between treatments, no significantdifferences could be detected between the BB and AB treatments, with the exception of the shoot mass of Medicago scuttelata v. Kelson (‘Kelson’ medic). The mean petiole NO3-N concentration for the period 1994/95 to 1998/99 tended to be lower in the AB treatment of a cover crop species compared to that of the BB treatment of the same species. In the case of ‘Kelson’ medic (BB) the petiole NO3-N and juice N concentrations were significantly higher than that of the control and weedchem. The juice N concentration of the control and weedchem was significantly less than thatof the faba bean treatments during 2000/01 and 2001/02, the Vicia dasycarpa Ten (grazing vetch) and ‘Kelson’ medic treatments during 2000/01, as well as that of Medicago truncatula Gaertn. (BB) and Trifolium subterraneum L. v. Woogenellup (BB) during the 2001/02 season. Wine quality did not differ between treatments

Cover Crop Management in a Chardonnay/99 Richter Vineyard in the Coastal Region, South Africa. 3. Effect of Different Cover Crops and Cover Crop Management Practices on Organic Matter and Macro-nutrient Content of a Medium-textured Soil

The trial was conducted over a period of 10 years (1993/94 to 2002/03) on a medium-textured soil in aChardonnay/99 Richter vineyard near Stellenbosch (33°55’S, 18°52’E), which is situated in the Coastal wine graperegion of the Western Cape, South Africa. Sixteen treatments, consisting of three cereals and five legumes, managedaccording to two cover crop management practices, were included. These treatments were compared to a control,in which no cover crop was sown and the weeds were controlled mechanically in the work row and chemically inthe vine row from bud break to harvest (approximately the first week of February). A treatment in which no covercrop was sown and full-surface post-emergence chemical weed control was applied from before bud break toharvest (BB) (weedchem) was also included. After five seasons, the soil organic matter (SOM) content in the 0 to300 mm soil layer increased in all the cover crop management treatments. In weedchem and in the control, SOMremained unchanged and decreased by 16% respectively. The SOM content in the 0 to 150 mm soil layer of thecover crop treatments was, with the exception of Vicia dasycarpa Ten. (grazing vetch), significantly higher than thatof the mechanically-cultivated control after a period of 10 years. The SOM content in the 0 to 300 mm soil layer ofSecale cereale L. v. Henog and the treatments in which the N-fixing cover crops were sown (with the exception ofgrazing vetch) was significantly higher than that of weedchem. The total inorganic N (TIN) concentration of the 0to 150 mm soil layer in the BB treatments of the two Medicago species and Trifolium subterraneum L. v.Woogenellup, as measured for the 1996/97 season during full bloom of the grapevines, was significantly higher thanthat of the control, weedchem, and the treatments in which full-surface chemical control was applied after budbreak (AB). The TIN concentration of the 0 to 600 mm soil layer in the AB treatment of a species, measured afterharvest in 2002/03, tended to be higher than that of the BB treatment of that species. The applied treatments hadno significant effect on the exchangeable K, Ca and Mg

Cover Crop Management in a Chardonnay/99 Richter Vineyard in the Coastal Wine Grape Region, South Africa. 1. Effect of Two Management Practices on Selected Grass and Broadleaf Species

The trial was conducted over a period of 10 years (1993/94 to 2002/03) on a medium textured soil in a Chardonnay/99 Richter vineyard near Stellenbosch (33°55’S, 18°52’E), situated in the Coastal Wine Grape Regionof the Western Cape. Sixteen treatments, consisting of three grain species and five N-fixing broadleaf species managed according to two cover crop management practices, were included. These treatments were compared to a control treatment, in which no cover crop was sown and the weeds were controlled mechanically in the work row and chemically in the vine row from the first week of September to the end of March (grapevine growing season).  A treatment in which no cover crop was sown and full surface post-emergence chemical control was applied during the grapevine growing season was also included. The different weed control actions were carried out during the first week of September and/or at the end of November, as well as mid October (1999/00 to 2002/03). Secale cereale L. v. Henog (rye), Avena sativa L. v. Overberg (‘Overberg’ oats), Avena strigosa L. v. Saia (‘Saia’ oats) and Vicia faba L. v. Fiord [only if sown annually and controlled chemically before bud break (BB)], showed the ability to produce,on average, significantly more dry matter during winter than the weeds in the region. The dry matter production of all the cover crops increased from the end of August to the end of November if left to complete their life cycles, with the exception of rye and ‘Overberg’ oats sown in early April. None of the cover crop species were able to reestablish successfully. Continuous effective suppression of winter growing weeds (less than 20% of the weed stand in the control) was achieved with ‘Overberg’ oats (BB) and ‘Saia’ oats (BB), while total suppression was achieved for six and five of the 10 years, respectively. Effective, long-term control of the summer growing weeds was obtained with rye (BB), ‘Overberg’ oats (BB) and ‘Saia’ oats (BB)

Cover Crop Management in a Sauvignon Blanc/Ramsey Vineyard in the Semi-Arid Olifants River Valley, South Africa. 2. Effect of Different Cover Crops and Cover Crop Management Practices on Grapevine Performance

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 (31o35’S, 18o52’E), situated in the semi-arid Olifants River Valley of the WesternCape. Fourteen treatments, consisting of three grain species and four legumes, managed according to two cover cropmanagement practices, were included. One management practice consisted of cover crops which were sown annuallyand full surface, post-emergence chemical control which was applied before bud break and when the berries reachedpea size (BB). The second management practice consisted of cover crops which were sown biennially. Post-emergencechemical 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 controlapplied 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 andchemically in the vine row from bud break to harvest (MC), were also applied. These treatments were compared toa control, in which no cover crop was sown and MC was applied. A treatment in which no cover crop was sown andBB was applied (weedchem), was also included. During the third growing season of the vines (1994/95), the grapevineshoot mass of the BB treatments of grazing vetch and Medicago truncatula Gaertn. v. Paraggio (‘Paraggio’ medic) wassignificantly more than that of the AB and MC treatments, with the exception of Secale cereale L. v. Henog (AB) andgrazing vetch (MC). The first harvest (1994/95) from the grapevines in the BB treatments was significantly higher thanthat of weedchem and the MC treatments. The grape yield of the BB treatments, grazing vetch (AB) and Ornithopussativus L. v. Emena (pink Seradella) (AB) was significantly more than that of weedchem and the control during the1997/98 season. The NO3-N concentration in the leaf petioles in all the cover crop treatments was, with the exceptionof the AB treatments of rye, M. truncatula Gaertn. v. Parabinga (‘Parabinga’ medic) and grazing vetch, significantlyhigher than that in weedchem and the control, as measured during the 1994/95 season. The NO3-N concentration inthe leaf petioles of the BB and AB treatment of a species differed significantly. The N concentration in the juice of thecover 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 ofthe juice in the BB and AB treatments of grazing vetch and pink Seradella was significantly higher than that of theMC treatments, two rye treatments, weedchem and the AB treatments of the other cover crops. The concentrationof Ca in the juice of the cover crop treatments was, with the exception of the pink Seradella treatments, significantlyhigher than that of weedchem and the control. Wine quality did not differ between treatments

Cover Crop Management in a Sauvignon Blanc/Ramsey Vineyard in the Semi-Arid Olifants River Valley, South Africa. 3. Effect of Different Cover Crops and Cover Crop Management Practices on the Organic Matter and Macro-Nutrient Contents of a Sandy Soil

The trial was conducted over a period of ten years (1993/94 to 2002/03) on a sandy soil in a Sauvignon blanc/Ramseyvineyard near Lutzville (31o35’S, 18o52’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 managementpractices, were included. One management practice consisted of cover crops which were sown annually. Full surfacepost-emergence chemical control was applied before bud break and again when the berries reached pea size (BB). Thesecond management practice consisted of cover crops which were sown biennially. Post-emergence chemical controlwas 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 controlapplied at the end of November (berries at pea size) was advanced to mid-October. Two treatments in which Avenasativa L. v. Saia (‘Saia’ oats) and Vicia dasycarpa Ten. (grazing vetch) were sown annually, controlled mechanically inthe work row and chemically in the vine row from bud break to harvest (MC), were also applied. These treatmentswere compared to a control, in which no cover crop was sown and MC was applied. A treatment in which no covercrop 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 ofthe 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 grapevinesin 1995/96 and significantly higher than that of the other treatments in the 150-300 mm soil layer. The TIN measuredin the AB treatments of grazing vetch and pink Seradella as measured after the grapevine harvest (1995/96), wassignificantly higher than that of the control, weedchem and cereal treatments in the 0-300 mm and 0-150 mm soillayers, 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 March2003. The TIN in the 150-300 mm soil layers of the AB treatments of pink Seradella and the two Medicago truncatulaGaertn. varieties, namely, Parabinga and Paraggio, was significantly higher than that of the control, weedchem andthe grain treatments. Potassium concentrations in the 0-150 mm soil layer of the two pink Seradella treatments, theAB treatment of rye, Medicago truncatula Gaertn. v. Paraggio and grazing vetch, as well as the 150-300 mm soil layerof grazing vetch (BB) and pink Seradella (BB), were significantly higher than that of the control, weedchem and ‘Saia’oats (MC) during March 1997

Cover crop management in a Sauvignon blanc/Ramsey vineyard in the semiarid Olifants River Valley, South Africa. 1. Effect of management practices on selected grass and broadleaf species

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 effect of fertiliser N rates on growth of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) grown at high soil water levels under controlled conditions

The response of perennial ryegrass and white clover to fertiliser N rates of 0, 30, 60, 120 and 180 kg N ha-1 when grown at soil water potentials of -10, -20, -25 and -35 kPa were investigated. Increasing fertiliser N levels from 0 to 120 kg N ha-1 resulted in increased (P=0.05) perennial ryegrass primary dry matter production (PDM) at the end of the first regrowth cycle (31 days). Ryegrass PDM yield was influenced (P=0.05) by soil water potential, with higher yields recorded at the -10 and -20 kPa treatments compared to the -25 and -35 kPa treatments. White clover PDM production was not influenced by N rate or soil water potential. Carry-over fertiliser N caused increased (P=0.05) ryegrass residual dry matter (RDM) yields as fertiliser N rate was increased from 0, 30, or 60 kg N ha-1 to 120 and 180 kg N ha-1, while clover RDM production increased as fertiliser N rate was increased from 0 to 180 kg N ha-1. Higher (-10 and -20 kPa) soil water levels caused increased ryegrass RDM production, a response not observed in clover. Total dry matter (TDM) production (the accumulative dry matter production during a 60 day period following fertiliser N application) of ryegrass was significantly increased as fertiliser N rate was increased from 0 to 180 kg N ha-1. Higher ryegrass TDM yields at-10 kPa and -20 kPa were recorded at the higher (120 and 180 kg N ha-1) N application rates, but water content did not influence TDM production at the lower (0, 30 and 60 kg N ha-1) fertiliser N application rates. Clover TDM production was not influenced by the treatments applied.Articl

Effect of soil tillage, crop rotation and nitrogen application rates on soil mineral-N levels in the Swartland wheat producing area of South Africa

Studies on nitrogen (N) levels in soil were conducted from 1997 to 2000 in a long-term tillage and crop rotation trial, which started in 1976. Three tillage methods namely conventional tillage (CT), tine tillage (TT), and no-tillage (NT) were compared. Crop rotation systems used were continuous wheat (WW) and wheat/lupin/wheat/canola (WLWC). Three rates of N-fertilisers (60, 100 and 140 kg N ha-1) were applied. All treatments received 60 kg N ha-1 at planting, while the 100 and 140 kg N ha-1 treatments received additional top-dressings of 40 kg N ha-1 at tillering and stem elongation stages respectively. Soil samplings were done at 14-day intervals, starting immediately before planting and continued till harvesting each year. Samplings at planting were done before N-fertiliser was applied and therefore regarded as pre-planting (Pp). The effect of tillage methods on mineral-N was variable and inconsistent among the soil samplings and years. During the four-year-period of this study, higher values of total mineral-N were found with conventional tillage at the pre-planting (Pp) samplings. Crop rotation did not significantly influence total mineral-N, which may be explained by the cultivation of a legume crop (lupins) once every four years only. In general the application of N-fertiliser resulted as expected in an initial increase in the mineral-N content of the soil. However, this was soon followed by a rapid decline as crops start to utilise the added nitrogen, resulting in values of less than 10 mg kg-1 soil during the grain filling stages with application rates of 60 and 100 kg N ha-1. These values may be regarded as deficient for grain yields of 4000 to 5000 kg ha-1.Articl

The effect of low soil temperature and fertiliser N rate on perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) grown under controlled conditions

The response of perennial ryegrass and white clover to soil temperatures of 6, 12 and 18°C, and to nitrogen applications equivalent to 0, 50, 100 and 150 kg N ha-1, were investigated under controlled conditions. Ryegrass primary dry matter production (PDM) at the end of the first regrowth cycle (31 days) increased as fertiliser N rate was increased from 0 to 100 kg N ha-1. Residual dry matter production (RDM) at the end of the second regrowth cycle (60 days) and total dry matter production (TDM) over the two regrowth cycles were increased by all N application rates tested. Although yield responses were less at 6°C compared to 12 and 180°C, results clearly showed that N applications could be used to stimulate dry matter production of ryegrass during the cool season. White clover PDM, RDM and TDM were significantly influenced (P0.05) by soil temperature resulting in lower yields at 6°C. None of the fertiliser N treatments tested resulted in significant reductions in clover PDM, RDM and TDM. Increasing fertiliser N rates increased (P0.05) the number of ryegrass tillers, but stolon growing points of white clover were not affected. Leaf nitrogen content at the end of the first regrowth cycle was higher than levels regarded as adequate for optimum perennial ryegrass and white clover dry matter production. Results suggest that fertiliser N rates as high as 150 kg N ha-1 applied at low temperatures will stimulate perennial ryegrass dry matter production without any direct negative effect on white clover productivity.Articl

Effect of soil tillage, crop rotation and nitrogen application rates on plant-N content of spring wheat (Triticum aestivum L.) in the Swartland wheat-producing area of the Republic of South Africa

Studies on nitrogen content in spring wheat were conducted during the 2000 and 2001 growing seasons as part of a long-term tillage and crop rotation trial. Four tillage methods were used, namely conventional tillage (CT), tine tillage (TT), minimum tillage (MT) and no-tillage (NT). Crop rotation systems used were continuous wheat (WW) and wheat/ lupine/wheat/canola (WLWC). Three rates of nitrogen fertiliser (60, 100 and 140 kg N ha-1) were applied as sub-plots. Wheat plants were sampled at tillering stage (S1), stem elongation (S2), flag leaf (S3) (2000 growing season only) and anthesis (S4). In general nitrogen content (% of plant component) decreased as the plant reached maturity. Nitrogen content expressed as g plant-1 and kg ha-1 was affected by tillage method in both growing seasons, but the response depended on the amount of precipitation during the growing season. During the low rainfall year, highest N contents were found in the NT treatment. In contrast to this, CT resulted in the highest N content during high rainfall years. Significant differences in total nitrogen content in the plant (g plant-1) due to crop rotation were observed only at the tillering and flag leaf stages. At both stages, plants from the wheat/lupine/wheat/canola system resulted in significantly higher values than those from the monoculture (wheat/wheat) plots. A non-linear increase in the N content of the wheat crop with an increase in the N-application rate from 60 to 140 kg N ha-1 indicated a decrease in N-use efficiency at higher application rates during both years.Articl