Masters Degrees (Agronomy)

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Browsing Masters Degrees (Agronomy) by Subject "Arid regions agriculture -- South Africa"

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    The influence of seed-drill choice on soil physical properties and crop performance in a semi-arid production region of South Africa
    (Stellenbosch : Stellenbosch University, 2020-03) Truter, Karen Joane; Swanepoel, Pieter Andreas; Strauss, J. A.; Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy.
    ENGLISH ABSTRACT: Producers following conservation agriculture principles rely on seed-drill equipment that place seed directly in the soil. Most producers are currently using tine openers to establish their crops but the interest in disc openers is increasing. The aim of this study was to determine the influence of the seed-drill opener on seedbed properties and crop performance. The study was conducted 35 km south of Swellendam in the Napky region of the southern Cape, South Africa in two production seasons (2018 and 2019). Barley (Hordeum vulgare L.), canola (Brassica napus L.) and wheat (Triticum aestivum L.) were seeded with seed-drills mounted with either double disc, tine or a combination of tines and single disc openers. Soil bulk density, gravimetric soil water content and unsaturated hydraulic conductivity were used as an indication of the influence of the seed-drill openers on the soil physical properties. Soil bulk density and gravimetric soil water content were determined 7, 30, 60, 90 and 120 days after seeding for a depth of 100 mm on the seeding row, while unsaturated hydraulic conductivity was only determined on days 7 and 60 after seeding. Soil bulk density varied between the tested seed-drills (p < 0.05), especially directly following the seeding operation. A tendency was noted that a decrease in soil disturbance, at the time of seeding, conserve more gravimetric soil water in the seed-furrow. Unsaturated hydraulic conductivity showed inconsistent results over the first growing season. Various crop parameters were evaluated to draw conclusions about the influence of seed-drill choice on crop performance. Seeding depth was determined on a few sampling dates from 16 days after seeding to calculate an average seeding depth. Seedlings were counted approximately every four days to determine the rate of emergence and survival. Biomass production was measured respectively 30, 60, 90, 120 and 150 days after seeding. By the end of the growing season, yield components were used to estimate the potential yield for each of the seed-drills, except for canola. Seeding depth was most accurate where the tine seed-drill was used for seeding purposes (p < 0.05). However, the direct influence of seeding depth on seedling emergence is not prevalent. Barley and wheat plant populations did not differ between the different seeddrills (p > 0.05), but lower canola populations were established with a double disc seed-drill (p < 0.05). Increased biomass production (p < 0.05) was noted towards the end of the growing seasons, where seeding took place with less soil disturbance (i.e. double disc seed-drill). The type of seed-drill and its associated opener will influence soil physical properties and crop performance to different extents, depending on the prevailing climatic conditions and the inherent soil physical properties.