2015 Cilt 9 Sayı 27
Permanent URI for this collectionhttps://hdl.handle.net/11452/19286
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Item Modeling yield loss in a tripartite canola-cover crop-weed system under varying nitrogen and seeding rates(Uludağ Üniversitesi, 2016-03-07) Hamzehzarghani, Habiballah; Kazemeini, Seyed-Abdolreza; Edalat, MohsenPossible use of cereal cover crops as a sustainable alternative weed control option in canola fields through optimizing cover crop and its density in canola-weed-cover cropping tripartite systems was modeled using a gamma density function with four parameters. The effect of competition between main crop (canola), cover crop (wheat or barley) and weeds on canola yield was studied in an experiment conducted in 2012/2013. Each cover crop was sown in four seeding rates: 0, 25, 50 and 75 percent under two nitrogen rates of 75 and 150 kg ha-1 . Weed suppression measured as canola relative yield was associated with the increase of seeding rate of cover crop according to a modified gamma density function. Parameters alpha, kappa, eta and lambda summarized the effect of N application on yield response under no cover crop conditions, measure of treatment effect on the curve amplitude, the plant density at which crop yield maximizes and the curve slope at the right tail which was an indication of the treatment effect on the rate of yield reduction beyond the seeding rate that maximized the crop yield, respectively. Model diagnostics and agreement analysis showed that the modified gamma density function described the functional response of the main crop to seeding rate of the cover crop equally well across a variety of treatment effects. Response curve analysis showed that in both levels of nitrogen, canola yield was more responsive to barley as cover crop when compared to winter wheat.