Increasing sweet orange growth in the winter nursery with supplemental light and heating

Authors: BISI, RAYANE - University Of Florida; ALBRECHT, UTE - University Of Florida; Bowman, Kim

Submitted to: Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2024
Publication Date: 8/24/2024
Citation: Bisi, R., Albrecht, U., Bowman, K.D. Increasing sweet orange growth in the winter nursery with supplemental light and heating. Horticulturae. 2024. 10(9):897. https://doi.org/10.3390/horticulturae10090897.
DOI: https://doi.org/10.3390/horticulturae10090897

Interpretive Summary: In the winter, citrus nursery production faces challenges due to shorter days and lower temperatures. We conducted a study to enhance citrus nursery production during winter. We examined the influence of supplemental LED light and various temperature conditions on the growth of bud grafted citrus trees. We used Washington Navel orange budded on Carrizo citrange and Rubidoux trifoliate rootstocks. Three lighting levels were studied, along with different heat levels and preconditioning treatments. The combination of light treatment and heating significantly affected scion shoot growth. Responses varied between the two rootstocks studied, and daylength extension positively impacted scion shoot growth at higher temperatures. The findings from this study offer valuable insights for citrus nurseries aiming to enhance young tree production in winter using supplemental LED light and heat.

Technical Abstract: Optimal light and temperature conditions play a crucial role in determining the growth and quality of nursery plants. In the winter season, citrus nursery production faces challenges as shorter days, lower light levels, and lower temperatures delay vegetative budbreak and scion shoot growth. With a goal to improve the production cycle in the citrus nursery, we initiated this study to evaluate the effect of supplemental LED light, combined with different temperature regimes, on the production of bud grafted citrus trees during the winter short days. Washington Navel orange (Citrus sinensis) was budded on Carrizo citrange (C. sinensis × Poncirus trifoliata) and Rubidoux trifoliate (P. trifoliata) rootstocks in the beginning of winter. Lighting was studied at three levels: 1) no supplemental light, 2) daylength extension to 16 hours, and 3) night interruption, in combination with two different levels of supplemental heat and without heat. Preconditioning light treatments were also evaluated. Air temperature and daily light integral were monitored from preconditioning to the end of the experiment. Plants were scored periodically for scion bud survival, vegetative budbreak, and scion shoot length up until 14 weeks after budding. The combination of light treatment and level of heating significantly affected the scion shoot growth. The responses to supplemental light and temperature also differed between the rootstock cultivars. Daylength extension to 16 hours increased the scion shoot growth at higher temperatures but did not affect scion shoot growth at low temperatures. Night interruption did not affect scion budbreak or growth in any temperature conditions. Light preconditioning treatment had a positive effect on the scion shoot growth, although the effect was moderate and variable. The results from this study provide valuable information for the citrus nursery to improve young tree production during the winter by combining supplemental LED light and heat.