A multiple-regression model of bulb onion yield in response to meteorological conditions in Gyeongsangnam province, Republic of Korea
Climate change is a challenge for onion growers because it has caused many physiological disorders and pest problems, resulting in unstable onion bulb productivity. We evaluated climate change from 1973 to 2017 in Gyeongsangnam province, Republic of Korea and analyzed the relationship between weather conditions and onion bulb yield from the 1991/1992 to the 2016/2017 growing seasons. The mean and maximum air temperatures significantly increased in all growth stages except for the root establishment stage (from early November to early December, phase II). During the plant vegetative stage (mid-February to mid-April, phase IV), the mean temperature increased at 0.35°C decade‑1. Precipitation was widely fluctuated year-to-year. Bulb yield rapidly increased during the 1980s with 2.51 Mg ha‑1 year‑1 (R2=0.683, P=0.003) and was stabilized during the 1990s and until the 2005/2006 growing season with 0.51 Mg ha‑1 year‑1 (R2=0.441, P=0.003). However, the yield was notably unstable and was inclined to decrease from 2006/2007 to 2016/2017 with -0.68 Mg ha‑1 year‑1 (R2=0.101, P=0.341). The bulb yield peaked in the 2008/2009 growing season at 83.9 Mg ha‑1, but was reduced to 60.8 Mg ha‑1 in 2016/2017. According to linear regression analysis of onion bulb yield, temperature, and precipitation in different growth stages from 1991/1992 to 2016/2017, onion bulb yield was positively related with mean and maximum temperature during the seedling stage (early September to late October, phase I) at P≤0.05 and P≤0.01, respectively, and mean temperature during the vegetable growth stage and bulb development stages (late April to mid-June, phase V) at P≤0.05. Higher mean, maximum, and minimum temperatures during the overwintering stage decreased onion bulb yield, but this trend was non-significant. Precipitation was not significantly related with onion bulb yield. Among multilinear regression models estimated from mean temperature, maximum temperature, minimum temperature, and/or precipitation from the phase I to phase V, a model of the best accuracy and high applicability with a root mean squared error of 5.012 Mg ha‑1 and a coefficient of determination (R2) of 0.768 and an adjusted R2 of 0.613 can be written as follows: Yield=5.419Tmax (I) - 1.847Tmax (II) - 5.138Tmax (III) + 3.817Tmax (IV) + 0.513Tmax (V) + 0.003P (I) - 0.027P (II) + 0.004P (III) + 0.056P (IV) - 0.016P (V).
Lee, J., Min, B., Yoon, S., Lee, M., Kim, H. and Hong, K. (2019). A multiple-regression model of bulb onion yield in response to meteorological conditions in Gyeongsangnam province, Republic of Korea. Acta Hortic. 1251, 81-90
climate change, yield prediction, growth stages, Allium cepa L