Browsing by Author "Smit, Ernst Hendrik"
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- ItemUtilisation of cover crops : implications for conservation agriculture systems(Stellenbosch : Stellenbosch University, 2019-04) Smit, Ernst Hendrik; Swanepoel, Pieter Andreas; Strauss, Johann; Stellenbosch University. Faculty of Agrisciences. Dept. of Agronomy.ENGLISH ABSTRACT: Cover crops have the potential to address some limitations in conservation agriculture systems with a Mediterranean climate. These limitations include, but are not limited to, a lack in crop diversity, herbicide resistant weeds, insufficient soil cover, and degraded soil. Mediterranean climates restrict cover crop production to the winter growing season when crops are normally planted. This increase the financial cost of cover crops as the implementation of cover crops replace one season’s production. In order to salvage some of the costs of cover crop production, the cover crops can be utilised. It is, however, not clear how utilisation of cover crops will influence the functional role of cover crops. This study aims to investigate how cover crops and the utilisation of cover crops affect the productivity of a system. A trial was conducted in 2016 in the Swartland region of South Africa, characterised by a Mediterranean-type climate. In the first year of the trial, two cover crop mixtures (a mixture containing mainly cereal crops and another containing mainly leguminous crops) were planted. Each of the mixtures were utilised in three ways: i) mowed and removed as hay, ii) grazed by sheep and iii) rolled and left unutilised. In the succeeding year (2017), wheat was planted on all the plots and a control was included (wheat on plots where wheat was cultivated for the previous two years). Cover crop utilisation reduced (p < 0.05) the quantity of soil cover, but not necessarily (p > 0.05) the amount of minerals in the soil cover. In addition to this, grazing of cover crops improved (p < 0.05) soil N. In a dry year cover crop cultivation did not increase (p < 0.05) the succeeding wheat grain production, irrespective of cover crop utilisation in the previous year. A mainly leguminous cover crop mixture, however, can increase (p < 0.05) the wheat grain protein content. The results indicate that utilisation of cover crops improve nutrient cycling. Cover crops do not always improve succeeding cash crop yield, which in turn could increase the risk on investment for producers. The implementation of cover crops improved (p < 0.05) cash crop quality, but not (p < 0.05) the grain yield of the cash crop. This indicates that the positive effect of cover crops on succeeding cash crops will not always compensate for the financial cost involved in cultivating cover crops. The only negative effect of grazing the mainly leguminous mixture was a reduction (p < 0.05) in the quantity soil cover, but the same treatment increased (p < 0.05) soil N. Despite the reduction in soil cover following utilisation, soil was still sufficiently covered according to conservation agriculture norms. This indicates that the utilisation of cover crops can generate an additional income and improve the economic viability of cover crop production.