Yield- and lodging-related traits are considered essential for improving rapeseed production; however, the interrelationship of these traits and their role in agronomic processes that promote rapeseed growth are not fully understood. The objective of the present study was to investigate the influence of plant density (D) and nitrogen (N) rates on morphological, physiological, and biochemical traits related to yield and lodging in rapeseed. To this end, we evaluated Huazha 9 for two consecutive growing seasons (2013–2014 and 2014–2015) under three plant densities (D15, 15 plants m−2; D30, 30 plants m−2; and D45, 45 plants m−2) and four N rates (N0, 0 kg N ha-1; N180, 180 kg N ha-1; N270, 270 kg N ha-1; and N360, 360 kg N ha-1). The experiment was laid out in a split-plot completely randomized design with three replications—plant density was applied in the main plots and N rates in the sub-plots. Our results demonstrated that the effect of plant density on seed yield and yield-related traits was inconsistent between the growing seasons, whereas that of N application was consistently positive. Lodging resistance significantly increased with increase in plant density in both growing seasons; however, the effect of N application was not consistent. Plant height was affected only by N application and reached a maximum at D15N270. The net photosynthetic rate was significantly affected by N application and D × N, reaching a peak at D15N180, whereas the radiation interception significantly increased with increasing the D × N, peaking at approximately 70–80% at D45N360.The oil content was significantly affected by N but not by plant density, whereas lignin content was significantly affected by plant density in both growing seasons and by N application in the 2013–2014 season. To the best of our knowledge, this is the first report on the correlation between lignin content and lodging resistance in rapeseed. Hence, this study implies that that D30N180 was the best combination of plant density and N rate for improving yield and lodging resistance in rapeseed.
Keywords:
Rapeseed, Yield, Lodging, Lignin, Nitrogen, Plant density
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