• Authors:
    • Fourie, J.
    • Joubert, M.
    • Freitag, K.
  • Source: SA Fruit Journal
  • Volume: 10
  • Issue: 1
  • Year: 2011
  • Summary: Five soil management practices applied in a micro-sprinkler irrigated 'Pink Lady' (Cripps Pink/M7) orchard established on a loam soil near Grabouw were evaluated from October 2003 to March 2010. Dry matter production by the cover crops at the end of September was higher under integrated soil management (IP) than under organic soil management (Organic) during 2004, 2007 and 2008, with the same trend being observed during 2005, 2006, and 2009. Cover crops in the IP and Organic treatments suppressed the winter growing weeds significantly over all seasons compared to treatments in which no cover crop was sown and weeds were slashed during the growing season of the trees (Weeds (IP) and Weeds (Organic) treatments). Except for September 2004, a similar result was achieved where a full surface straw mulch was packed out annually during October, followed by hand weeding during the growing season of the trees (Straw Mulch (Organic) treatment). Summer growing weeds were controlled effectively by the Cover Crop (IP) and Straw Mulch (Organic) treatments. Weeds (IP) and Weeds (Organic) caused broad leaf weeds to disappear and perennial grasses to dominate the weed spectrum. Although not as drastic, a similar trend developed in the Cover Crop (Organic) treatment. In contrast, annual weed species became dominant where Cover Crop (IP) was applied. All soil cultivation practices caused changes in the weed spectrum, with species dominance shifting with time. This aspect of weed control should be studied more extensively in future.
  • Authors:
    • Muchaonyerwa, P.
    • Chiduza, C.
    • Murungu, F. S.
  • Source: African Journal of Agricultural Research
  • Volume: 6
  • Issue: 24
  • Year: 2011
  • Summary: Use of legume cover crops has been reported to improve maize productivity through various mechanisms that include improved soil mineral N supply and weed control. However, in the smallholder irrigation farming sector, where maize is the staple crop, strategies for intercropping summer legume cover crops are often a challenge for farmers. Field experiments were conducted in a warm-temperate region of South Africa during the summer season of 2007/08 and 2008/09 to investigate the effects of strip intercropping patterns (3:2; 4:2 and 6:2 patterns) on the productivity of maize (cv. PAN 6479) together with mucuna or sunnhemp. The strip-intercrop patterns did not result in improved soil mineral N or weed control. Maize yields from rows adjacent to the cover crop strips were significantly (P
  • Authors:
    • Odhiambo, J. J. O.
  • Source: African Journal of Agricultural Research
  • Volume: 6
  • Issue: 1
  • Year: 2011
  • Summary: Much of the smallholder farming sector in Limpopo province of South Africa is located on infertile degraded soils, with nitrogen being one of the predominantly deficient nutrient. The use of green manure legume cover crops in combination with Nitrogen (N) fertilizers is one option for improving N inputs into such farming systems. The objectives of this study were to (1) screen a number of green manure legume cover crop species, mucuna (Mucuna pruriens); sunhemp (Crotalaria juncea), lab-lab (Lablab purpureus); cowpea (Vigna unguiculata) and butterfly pea (Clitoria ternatea) in order to determine their suitability for the region and (2) to determine the effect of the green manure and nitrogen fertilizer on maize yield. The legumes were screened during the winter seasons of 2005 and 2006 and the summer seasons of 2005 - 2006 and 2006 - 2007. The best-bet legumes (mucuna, sunhemp and lab-lab) were then evaluated to determine their effect on maize grain yield with or without nitrogen fertilizer. The treatments imposed were mucuna, sunhemp, lab-lab, and a control with (75 kg N ha(-1)) or without (0 kg N ha(-1)) N fertilizer. Maize was harvested at maturity to determine the grain yield. In the screening trials, legume biomass yield ranged between 41 to 1,672 kg ha(-1), while the N content ranged between 2 to 58 kg N ha(-1) in the winter trials. In the summer trials, biomass yield ranged from 899 to 13,586 kg ha(-1), while the N content ranged between 27 to 302 kg N ha(-1). Maize yield ranged between 4.0 to 6.4 tons ha(-1) in the 2006 - 2007 seasons and between 5.8 to 8.4 tons ha(-1) in the 2007 - 2008 season. Control (-N) treatment had the lowest yield in both seasons. Overall, legume treatments, with or without N fertilizers produced between 19 to 58% more grain yield than control (-N). Of the green manure legumes screened, mucuna, lablab and sunhemp seem to be the most suitable green manure legume cover crops for this area and should be planted in the early summer season to maximize biomass production and N accumulation. Use of green manure legumes has the potential to increase maize yield in smallholder farms in Limpopo province.
  • Authors:
    • Merwe, S. van der
    • Verreynne, S.
  • Source: SA Fruit Journal
  • Volume: 10
  • Issue: 2
  • Year: 2011
  • Summary: Sunburn is a major problem on early maturing mandarins such as 'Miho Wase' Satsuma. Currently, optimal irrigation during critical periods and shade nets are the only measures to reduce losses due to sunburn. Previous work using particle film technology (kaolin) on citrus to reduce sunburn was very effective, but the formulation used resulted in insect repercussions. The objective of the study was to determine if products such as Screen TM, Vapor Gard, Silicon and Raynox TM can reduce tree canopy temperature and thereby reduce sunburn on 'Miho Wase' Satsuma mandarins. All treatments were applied three times between December 2009 and January 2010. Screen TM reduced the sunburn incidence (fruit per tree) by 50%, possibly due to reductions in leaf temperature by 2.53C and fruit temperature by 1.73C, without a negative effect on fruit quality. Screen TM increased the sugar content of fruit. Vapor Gard increased fruit temperature, reduced the sugar content of the fruit, and increased sunburn incidence by 16%. Raynox TM, Silicon, and the combination of Screen TM and Vapor Gard had no effect on sunburn incidence.
  • Authors:
    • Risede, J.-M.
    • Foster, J.
    • Rhodes, R.
    • Berry, S. D.
    • van Antwerpen, R.
  • Source: International Journal of Pest Management
  • Volume: 57
  • Issue: 4
  • Year: 2011
  • Summary: Plant-parasitic nematodes cause significant yield losses to sugarcane crops in South Africa. The currently available chemicals for nematode control are both expensive and potentially detrimental to the environment. Various alternative crops have been reported to reduce the numbers of plant-parasitic nematodes. Mindful of this, we evaluated 27 cover crops in pot trials to assess their host status to important plant-parasitic nematodes of sugarcane. All of the crops tested in pots hosted significantly lower numbers of Pratylenchus than did sugarcane. Crops such as cowpeas, tomato and grazing vetch were good hosts for Meloidogyne and would not be good choices as part of a sugarcane rotation system in heavily-infested soils. Conversely, crops such as oats, wheat, forage peanuts and marigolds reduced numbers of Meloidogyne. Velvet beans increased the abundance of Helicotylenchus, a beneficial nematode genus. A field trial was also conducted to study the effect of different cover cropping sequences. Our results show that changes in nematode communities occurred within three months of growing these crops and often remained low for the duration (the remaining 15 months) of the crops' growth. Nematodes such as Pratylenchus and Tylenchorhynchus were significantly lowered and remained so for the duration of the trial.
  • Authors:
    • Lecler, N. L.
    • Tweddle, P. B.
  • Source: Proceedings of the Annual Congress - South African Sugar Technologists' Association
  • Issue: 83
  • Year: 2010
  • Summary: Many guidelines and recommendations for sugarcane farming are aimed at achieving a large number of ratoon crops. One of the reasons for this is that the replanting costs can be considerable when a field is conventionally tilled and replanted. Thus, delaying reestablishment makes financial sense provided the cost savings are greater than any yield and revenue penalties. An alternative is to introduce a controlled traffic and zero-till farming system (CTF), thereby lowering re-establishment costs and potentially allowing for fewer ratoon crops and more frequent green manure or break crops. A rigorous yield, sucrose content, costing and cash-flow analysis, based on published research findings and detailed costing of representative machinery, showed that a CTF system with only three ratoon crops was far more profitable than a conventional farming system involving eight ratoon crops and more intensive tillage operations. A doubling in profitability was shown when the yield benefits reported with break crops and the yield decline rates reported under conventional farming systems were included in the analysis. Substantial gains in water use productivity were also shown, up to nearly 80% improvement over a conventional farming system. Adoption of a CTF system with only three ratoon crops is therefore highly recommended and should be taken very seriously by decision-makers in the sugarcane industry.
  • Authors:
    • Heerden, P. S. van
    • Singels, A.
    • Rensburg, L. D. van
    • Annandale, J. G.
    • Jager, J. M. de
    • Inman-Bamber, N. G.
    • Durand, W.
    • Gree, G. C.
    • Crosby, C. T.
    • Schulze, R. E.
  • Source: South African Journal of Plant and Soil
  • Volume: 27
  • Issue: 1
  • Year: 2010
  • Summary: Mathematical simulation of crop growth and water relations has become indispensable to agricultural science and practice. A critical assessment of how modelling has contributed to the development of crop science and to the management of crop production and natural resources in South Africa (SA) over the past 25 years could give new perspectives on the benefits derived from modelling, the appropriateness of approaches employed and the best way forward. The initial objectives of the major SA modelling initiatives (ACRU, BEWAB, CANEGRO, CERES, PUTU, SAPWAT, SWB) dictated the approaches that were followed and determined their impacts. Significant advances were made with regard to improved understanding of crop growth and water use and adapting models for local conditions such as dryland grain crop production under very low rainfall. Modelling provided invaluable support for strategic investigations into the impacts of climate change, land use and water use. Many of the models succeeded in providing much-needed information to improve tactical and operational management of irrigated and dryland agriculture. Some models have been (and are being) used operationally to forecast crop production (maize, wheat and sugar) and to monitor droughts in natural vegetation, adding value to the respective industries. Modelling has formed, in some cases, an integral part of tertiary education in crop science and hydrology. This should be strengthened to build more capacity to address the ever-increasing complexity of challenges in agriculture. The review identified factors that are crucial for modelling to maintain effective impacts on the science and practice of crop production and natural resource use. These were excellent scientific leadership, long term funding, effective collaboration between local and with international groups, expertise on local agronomy and high quality experimental data for model testing and adaptation. Future modelling efforts should explore opportunities to integrate information obtained from technologies such as remote sensing and genomics.
  • Authors:
    • Przybylowicz, W.
    • Mesjasz-Przybylowicz, J.
    • Cramer, M.
    • Hawkins, H.
    • Louw, E.
    • O'Brien, C.
  • Source: Acta Horticulturae
  • Issue: 869
  • Year: 2010
  • Summary: Utilisation of previously cultivated land for Proteaceae crops is a viable alternative to using pristine land. However, cultivated lands have usually been fertilized and typically have soil [P] unsuitably high for Proteaceae, resulting in P toxicity. After establishing that the main effects of P toxicity on the shoot were increased leaf P and Mn, but reduced leaf Fe and Zn, it was hypothesized that binding soil P and providing additional Fe and Zn to leaves would ameliorate P toxicity. Various soil and leaf amendments were tested for their efficacy in reducing soil P in unplanted lands, or ameliorating or preventing P toxicity in lands or pots planted with Protea 'Sylvia'. In an unplanted field, deep ploughing to 50 cm reduced available P from 16213 to 8.82.6 mg P kg -1 soil, i.e. by 95%. Sowing two seasons of the cover crops oat and lupin also greatly reduced available P (80%) whilst Al 2(SO 4) 3 application (278 g m -2) reduced available soil P by 80-65% depending on initial soil [P]. Ploughing was associated with disadvantages such as reduced cations and possible disruption of microbial populations. Thus use of cover crops or, for more immediate reduction in available soil P, aluminium application may be preferable. Application of Al 2(SO 4) 3 was also shown to be effective in prevention and amelioration of P toxicity symptoms in Protea 'Sylvia' in the field, while a Fe-containing compound 'OX' and a Fe/Zn containing foliar spray were only effective in preventing P toxicity in a pot experiment. Calcium sulphate was not effective as a P-binder in the field. Different agents may be used for different requirements but Al 2(SO 4) 3 application was effective in both prevention and amelioration of P toxicity.
  • Authors:
    • Muchaonyerwa, P.
    • Chiduza, C.
    • Murungu, F. S.
  • Source: African Journal of Agricultural Research
  • Volume: 5
  • Issue: 13
  • Year: 2010
  • Summary: Production of large biomass yields and weed suppression from cover crops have been major constraints affecting success and uptake of conservation agriculture technologies by smallholder irrigation farmers. A field study was undertaken to evaluate biomass accumulation and N uptake by oats ( Avena sativa), grazing vetch ( Vicia dasycarpa), faba bean ( Vicia faba), forage peas ( Pisum sativum) and Lupin ( Lupinus angustifolius) and their winter weed suppression efficacy in the 2007 and 2008 winter seasons. Cover crops were grown at two fertiliser levels: no fertiliser and fertilized. Control plots were included where no cover crop was grown. At the end of each winter season, glyphosate was applied to kill the cover crops and maize planted. Oats, grazing vetch and forage pea's cover crops produced mean dry weights of 13873, 8945.5 and 11073 kg ha -1 respectively while lupin had the lowest dry weight of 1226 kg ha -1. Oats responded to fertilisation while, there was little or no response from the other cover crops. Oats and grazing vetch also reduced weed density by 90 and 80% respectively while lupin only reduced weed density by 23% compared with the control plots. Grazing vetch fixed a mean of 112 kg N ha -1. The results suggest that legumes such as grazing vetch and forage peas may be grown to maximise biomass yields with minimal fertilizer inputs. Amount of biomass produced was a major factor in controlling winter weeds, while there was a progressive decline in the winter weed burden from the first to the second season. The low C:N ratio of grazing vetch (
  • Authors:
    • Kalungu, J. W.
    • Monteiro, R. O. C.
    • Coelho, R. D.
  • Source: Ciência Rural
  • Volume: 40
  • Issue: 10
  • Year: 2010
  • Summary: This paper reviews various irrigation technologies in both South Africa and Kenya that enable improvements in their socio-economic conditions. The two countries are located in semi-arid areas that experience extreme fluctuations in the availability of rain water for plant growth. Population growth exceeds the ability to produce food in numerous countries around the world and the two countries are not an exception. This experiment examined the constraints that farmers face and the role of government and nongovernmental organization in the uptake of modern technologies for irrigation. Detailed mechanisms and options to secure sustainable irrigation which are economically viable are considered. Despite the higher production of cereals and grains, fruits, and flowers also thrive in the two countries. Total irrigated area, crops grown and irrigation systems used in the two countries are discussed.