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Title The effect of soil residue cover on medicago pasture establishment and production under conservation agricultural practices
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Publication Date
Date Available
Degree MSc
Discipline/Department Agronomy
Degree Level masters
University/Publisher Stellenbosch University
Abstract ENGLISH ABSTRACT: Annual medic pastures play an important role in conservation agriculture (CA) practices in the Western Cape, because of the beneficial role it plays in rotation systems and the fact that it can re-establish on its own. In the Overberg medic pastures are the main pasture short rotation crop, but farmers in recent years shifted away from including medics. This was due to unsuccessful re-establishment and a visible decrease in dry matter production. This trend started after CA practices were implemented for a few years. A field study conducted during 2013 investigated medic re-establishment and production following a wheat, barley, oat and medic pasture production year ( WM, BM, OM and MM) of which residues were left on the soil surface at different cover percentage levels (100%, 75%, 50%, 25% and 0%). The objective of this study was to determine what the effect of different amounts of residues was on annual medic re-establishment and production. Data from this study suggest that management of annual medic pastures should aim to re-sow the medic pasture if plant count drops below 78 pants per square meter. Weed management is of cardinal importance as it competes for resources, light and space and decrease medic pasture re-establishment and production. The data also indicates that the wheat/medic sequence is the best option when applying a short cash crop/annual pasture cropping system. Producers should manage their animals to ensure that a 50% to 75% cover is left on top of the soil following the grazing of residues during the summer months. The study in 2013 should have been replicated, but due to the low levels of re-establishment and production a decision was made to re-plant the trial sites. The field study conducted during 2014 investigated the medic/clover establishment and production following a re-plant. Medics were replanted following a W, B, O and M season, respectively. Residues again were manipulated to different cover percentages (100%, 75%, 50%, 25% and 0%). The objective was again to look at the amount and type of residues on medic/clover establishment and production following re-plant. Data from this study indicated that it might be advisable for annual medic/clovers to be re-sown after a cereal production year rather than a medic pasture year. With the production of medic/clover pastures not being affected by the residue cover percentage, a 100% residue cover following re-plant is best in rotations, if the optimal effect of CA wants to be observed. If animals are included in the production cycle, grazing of residues during summer months can occur until 50% cover is left. Soils will take longer to reach its potential, but by including animals the gross margin is more stable year on year. Two supplementary studies were conducted to investigate the germination of annual medics under controlled conditions. The objectives of the first supplementary study was to investigate the physical barrier effect of residues at different percentage cover (100%, 75%, 50%, 25% and 0%) and a possible…
Subjects/Keywords Conservation agriculture; Allelopathy; Medicago; UCTD
Contributors Strauss, Johann A.; Pieterse, P. J.; Stellenbosch University. Faculty of Agrisciences. Dept. of Agronomy
Language en
Rights Stellenbosch University
Country of Publication za
Format x, 110 pages : illustrations
Record ID handle:10019.1/97055
Repository stellenbosch
Date Indexed 2018-01-05

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