Research Articles (Agronomy)

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Browsing Research Articles (Agronomy) by Subject "Canola -- Yields"

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    High nitrogen rates do not increase canola yield and may affect soil bacterial functioning
    (American Society of Agronomy, 2019) Becker, Frederick; MacLaren, Chloe; Brink, Casper J.; Jacobs, Karin; Le Roux, Marcellous R.; Swanepoel, Pieter Andreas
    Nitrogen fertilization has a fundamental role in agricultural productivity. However, injudicious N applications to crops are common. It is important to ensure the minimum N required for satisfactory crop growth is applied but that excess amounts are avoided due to potential impacts on agroecosystem functioning. Nitrogen at 0, 60, and 150 kg ha-1 was applied as limestone ammonium nitrate to plots arranged in a randomized complete block design, on three farms to determine the impact of rate and temporal distribution of fertilizer on canola (Brassica napus L.) production in South Africa, and the effect of N fertilizer application on the composition and diversity of soil bacterial communities. The amount and distribution of N had only minor effects on canola growth (P < 0.05) and no effects on yield or harvest index. Splitting fertilizer into two or three applications throughout the season resulted in more mineral N available in the soil later in the season. Increasing the N rate from 60 to 150 kg ha-1 had a significant impact on bacterial community composition. The lower rate favored bacteria that are more able to break down N-containing carbon sources. No effects of fertilizer amount or distribution were observed on either N fixation potential (number of nifH gene copies) or bacterial community diversity. Overall, a low rate of N fertilizer split into multiple applications is recommended for canola production, as higher rates do not increase yield and may have a detrimental impact on soil carbon and nitrogen cycling.
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    Seed-drill opener type and crop residue load affect canola establishment, but only residue load affects yield
    (American Society of Agronomy, 2019) Swanepoel, P. A.; Le Roux, P. J. G.; Agenbag, G. A.; Strauss, J. A.; MacLaren, C.
    Core Ideas Canola establishment can be affected by the residues of the previous crop. Different planting tools may handle crop residue differently. Tine and disc furrow openers at different residue loads were tested. Canola performed best when established with tine openers and when residue load is low. Handling crop residue during planting operations is a challenge to conservation agriculture (CA) farmers worldwide. It remains unclear which tools are most effective in which conditions. Canola (Brassica napus L.), an oilseed crop widely used in rotation with cereals, is particularly sensitive to seedbed conditions, and thus may be influenced by residue loads and the choice of seed-drill openers. To identify optimal planting practices, this study compared the performance of disc and tine openers on canola establishment, growth, and yield under differing residue loads in a Mediterranean-type climate region. First, soil disturbance caused by disc and tine openers was evaluated to assess their effect on seedbed conditions; and second, the interacting effects of the openers with different residue loads was investigated. Tine openers and low crop residue loads resulted in the best (P < 0.05) canola establishment. However, canola at reduced plant populations compensated in both biomass and grain yield, so that no yield differences resulted from different opener types, and only small yield differences occurred between residue loads (P > 0.05).