Masters Degrees (Agronomy)

Permanent URI for this collection

https://scholar.sun.ac.za/handle/10019.1/521

Browse

Browsing Masters Degrees (Agronomy) by browse.metadata.advisor "Brand, T. S."

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Developing management strategies to support sustainable production of lucerne in long-rotation cropping systems
    (Stellenbosch -- Stellenbosch University, 2020-03) Van der Westhuizen, Christoff George; Swanepoel, Pieter Andreas; Labuschagne, Johan; Brand, T. S.; Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy.
    ENGLISH ABSTRACT: Lucerne (Medicago sativa L.) forms part of long-rotation cropping systems integrated with livestock in the southern Cape of South Africa. The lucerne phase is five to seven years long, followed by five to seven years of cash crops. Lucerne swards allow for the integration of livestock into cropping systems, improved resource utilisation, is a high-quality animal forage, biologically fix N, break disease cycles and may improve subsequent cash crops yields. However, some farmers consider excluding lucerne from crop production cycles. The main reasons for the exclusion of lucerne swards are low summer and winter herbage production due to moisture stress and lucerne’s natural winter dormancy. Low herbage production during these periods create considerable fodder flow deficits and make the management of fodder flow programmes challenging for farmers. The oversowing of dryland lucerne swards with annual winter growing forage crops, to create lucerne-based multiple species pastures, was investigated to determine if fluctuations in fodder flow programmes could be reduced through increased winter herbage production. Field experiments were conducted at Tygerhoek Research Farm (Riversonderend) during the 2018 and 2019 growing seasons. Both single species treatments and mixes were oversown into an existing lucerne base. Single species treatments included black oats, forage barley, stooling rye, Westerwolds ryegrass, forage radish and canola. Mixes consisted of various combinations of hybrid ryegrass, Italian ryegrass, forage barley, black oats, various annual Medicago and clover species, vetch and forage radish. The effect of oversown species and mixes on herbage production, pasture and soil quality was monitored for the duration of this study. Drought conditions after oversowing restricted the performance of the oversown species and mixes and had a knock-on effect that persisted for the duration of this trial. No treatment had a higher herbage yield to that of the control at any stage in the growing season (p>0.05). Small grains and mixes that contain small grains did however show the most potential to improve herbage production, especially in late winter. Due to poor performance of oversown treatments, herbage samples mainly consisted of the lucerne base and ryegrass, both as an oversown species and weed. The relatively similar species composition from different treatments yielded no clear and or obvious treatment that improved pasture quality, however, grazing management ensured that all treatments were of a high quality at the time of sampling. Similar returns of organic matter, both quantatively and qualitatively resulted in soil quality that was similar between all treatments. Different results may be obtained if oversown species establish well and this study should be replicated in years of normal rainfall distribution to fully comprehend how changes in pasture composition will affect herbage production and pasture quality. Soil physical, chemical and biological parameters should also be monitored over an extended period of time as changes in soil quality may take several years in Mediterranean climates.