Masters Degrees (Agronomy)

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Browsing Masters Degrees (Agronomy) by browse.metadata.advisor "Denner, Freddie"

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    The use of a starch-based superabsorbent polymer to support and optimise potato production in the sandy soils of the Sandveld production region in South Africa.
    (Stellenbosch : Stellenbosch University, 2023-03) Smit, Lome; Swanepoel, Pieter Andreas; Steyn, Martin; Denner, Freddie; Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy.
    ENGLISH ABSTRACT: Trends in agriculture are rapidly shifting towards more sustainable approaches. This is no different for the ecologically sensitive Sandveld region, where agricultural activities put pressure on the indigenous biodiversity and available resources. Potato production in the Sandveld region is highly reliant on groundwater resources for irrigation purposes, due to the low annual precipitation coupled with very high evaporative demands, especially in summer months. Additionally, potato crops are sensitive to water stress and the crop’s poorly developed rooting system is inefficient in extracting the already low plant available water in sandy soils. The aim of this study was to evaluate the potential of the biodegradable superabsorbent polymer, Zeba™, to support and improve potato production systems in semi-arid, drought prone areas. This study was approached by means of a field trial as well as a supplementary pot trial. In the field trial, four rates of Zeba™, were applied in- furrow at planting, and compared to a control. Soil water content measurements showed that the soil layers from the treatments contained more moisture than the control. Generally, increased potato tuber yield (P<0.05) was observed with increasing rates of Zeba™, except for the highest treatment rate, which had a similar yield as the control (P>0.05). The application of Zeba™ did not adversely affect the tuber quality. The increased tuber yields resulted in improved resource-use efficiencies. The water-use efficiencies, as well as nutrient-use efficiencies were either higher, or equivalent, to values reported for previous research in the area. Three application rates, similarly as three of the rates in the field trial but adjusted for a 15 cm pot, were compared to a control in a pot trial. The water holding capacity of the soil and polymer system was assessed one day, and three days after a weekly irrigation event. The trial was run over a twelve week period. The results showed that both the treatment rate and the time intervals had a significant influence on the water holding capacity of the soil. Similar to the findings of the field trial, the water holding capacity increased with an increase in product applied. The use of the superabsorbent polymer had a more pronounced effect on the water holding capacity as the soil dried out after the irrigation event, due to its superior ability to retain water compared to the large pores of sandy soils. In comparison to the control, the use of this product retained more water on the third day after irrigation than on the first day after irrigation. Although a decrease in water holding capacity was observed as the trial progressed, there was no clear indication that it was due to a reduction in the polymer's absorption ability from degradation. The decrease observed is ascribed to the increase in temperature, which led to a higher evaporation rate. Zeba™ successfully improved potato production in the Sandveld by increasing the water holding capacity of the sandy soils, leading to an increase in fresh tuber yield and improved resource use efficiencies. A treatment rate of 10 kg ha⁻¹ of Zeba™ is recommended as optimal to support and optimise potato production in the Sandveld region. This product could also be used to sustain production in other semi-arid regions and drought prone areas, with similar soil textures, when water stress limits production.