Masters Degrees (Horticulture)

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Browsing Masters Degrees (Horticulture) by Author "Burger, Jani"

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    Quantifying the role of soil microbial activity in cover crops on newly established fruit trees in the Western Cape
    (Stellenbosch : Stellenbosch University, 2022-04) Burger, Jani; Lotze, Elmi; Le Roux, Marcellous; Stellenbosch University. Faculty of Agrisciences. Dept. of Horticulture.
    ENGLISH ABSTRACT: Limited research is available on the role of cover crops in newly established deciduous fruit orchards in South Africa. Thus, three field studies were conducted to evaluate the contribution of cover crops towards soil health/fertility. The effect of cover crop combinations on soil characteristics (mineral composition, soil moisture, soil compaction, water holding capacity, microbial activity and tree performance) and the contribution towards weed suppression and biomass production for mulching in a perennial orchard were quantified during two and three consecutive seasons in two locations. In addition, soil microbial activity and diversity were quantified with three locally available methods (Molecular fingerprinting, CO 2-burst test and gas chromatography). A two-year field study (Trial 1 and 2) was conducted in Stellenbosch, (33°56'51.27" S 18°52'19.29" E) and a three-year field study (Trial 3), in Elgin (34°09’16.83’ S, 19°02’28.01” E), Western Cape. Trial 1 (Multi species: forage rye, radish and white mustard) and trial 2 (Single specie: forage rye) comprised four treatments each: i) Control (natural vegetation), ii) Cover crop with no fertilizer application (MNFA; SNFA), iii) Cover crop with a single organic fertilizer application (MSFA; SSFA) and iv), Cover crop with a double organic fertilizer application (MDFA; SDFA). Trial 3 consisted of five annual winter cover crop treatments: i) Phacelia (PC) ii) Forage rye & vetch (FRVC) iii) Forage radish & white mustard (FRWMC), iv) Forage barley & peas (FBPC) v), Forage rye (FRC). Cover crops provided a significantly higher above- and below ground biomass compared to natural vegetation in trial 1 and 2, however, biomass differed amongst cover crop treatments. Biomass production differed significantly between cover crop treatments in trial 3. FRC performed the best, followed by FRVC and FRWMC. Crop species were the primary factor in plant performance and other factors contributed less towards biomass. However, weed suppression efficiency was affected by cover crop biomass and species. In trial 3, Forage rye, in combination or monoculture, performed the best in terms of consistency, biomass for mulching purposes, root length and weed suppression. Cover crops did not affect tree performance at this stage but should be monitored in future when tree roots will reach the work row. Cover crops directly contributed towards stimulation of the microbial community and conserved soil moisture compared to the control (natural vegetation) during spring. However, from our results it was evident that soil is an interlinking system and that it should be managed holistically in terms of soil physical, chemical and biological components. A long-term study should be initiated to evaluate the effect of using cover crops to improve soil health (Soil physical, chemical and biological interrelationship) and how improving the soil biological component will contribute to an alternative system such as farming with nature, minimizing external inputs, building soil structure and providing nutrient dense food.