Effect of wide-narrow row arrangement and plant density on yield and radiation use efficiency of mechanized direct-seeded canola in Central China

Direct-seeding is an effective canola cultivation method for saving production costs compared with transplanting seedling. The aim of this study was to understand the effects of wide-narrow row arrangement and of plant density on canola yield as well as its related parameters under mechanized direct-seeding farming system. A 3-year field experiment was conducted to evaluate the influences of different row spacing arrangements and plant densities on seed yield and canopy radiation use efficiency in three growing seasons (2009-2012). Treatments included two levels of plant densities (15 and 45 plants m−2), in combination with six levels of row spacing arrangements (three uniform row spacings and three wide-narrow row spacings). Results showed that the wide-narrow row arrangements of “20 + 20 + 40” cm (S6) increased average seed yields by 10% above the conventional 30 cm spacing (S2) in three experimental seasons. The treatment of “17.5 + 17.5 + 17.5 + 35 + 17.5 + 17.5 + 17.5 + 60” cm (S4) was exclusively designed as a wide-narrow row plantation for purpose of mechanization management, but yield of S4 did not decrease compared with S2. Meanwhile, plant density of 45 plants m−2 produced more yield than that of 15 plants m−2 by 4% in 2009-2010, by 7% in 2010-2011 and by 10% in 2011-2012. More effective pods per plant (about 17%) were achieved in wide-narrow row arrangements comparing with uniform ones, which were further supported by higher leaf area index and radiation use efficiency. S6 had 10-28% greater radiation use efficiency than S2 in three seasons. Hence an appropriate wide-narrow row arrangement could not only intercept more favorable photosynthetic active radiation, but also led to record substantially higher above-ground biomass accumulation (22%-33%) and more seed number per m2 (approximately 28%) compared with S2. Based on yield performance, the combination of 45 plants m−2 and S6 is the optimal scheme for canola production, and S4 is a promising alternative for planting mechanization under direct-seeding cropping system in Central China.