Effects of Greenhouse Environmental Factors on the Productivity of Summer-cultivated Sweet Pepper and Influential Factors

This study was conducted to analyze the effects of summer greenhouse environmental factors on the productivity of sweet pepper (Capsicum annuum L.) and to determine the influential factors. Two sweet pepper export farms in Gangwon-do (FIn in Inje and FCh in Cheorwon) were surveyed during 2021. The flowering of sweet pepper started in March. FIn undertook two-stemmed cultivation for 35 weeks and FCh utilized three-stemmed cultivation for 31 weeks. The amount of accumulated solar radiation gradually increased from the first flowering period, peaking in July, after which it decreased to about 60% due to frequent rainfall in August. The temperature was high in July, with the day temperature exceeding 30°C and the night temperature being over 21°C. The night temperature increased to as high as 26°C from July 4 to August 13. An analysis of the growth characteristics showed that FIn has a shorter flower length, a thinner stem diameter, and a shorter internode compared to FCh. The relative internode ratio of FIn was 138% for group 1, which is significantly higher than that of FCh. However, the ratio became lower than that of FCh from group 2 and significantly shorter for group 4, reaching 80%. The second half productions of FIn and FCh were 36.1 and 39.9% of the total production rates, respectively. Both farms showed sharply low fruit-set rates in group 5 along with very low harvest rates in groups 4 and 5. It was noted that the low fruit-set rate and harvest rates for groups 4 and 5 led to low yields in the second half of the year. Multiple regression analysis results showed that daytime temperatures and solar radiation levels were positively linked to production levels, while night-time temperatures and growing degree days (GDD) (24h-mean temperature minus 10) were negatively linked. Greater influences were observed in the following order: night-time temperature, solar radiation, GDD, and daytime temperature. Based on the obtained results, it is recommended to keep the 24h-mean temperature in the optimal range by keeping night-time temperatures lower while minimizing the decrease in solar radiation in July when the temperature is high in order to secure production in the second half of the year for summer-cultivated sweet pepper.