Effects of winter greenhouse microclimate on butterhead lettuce (Lactuca sativa var. capitata)

A study was conducted to establish appropriate microclimate conditions in tunnel greenhouses during the winter period located at Pietermaritzburg, KwaZulu-Natal, South Africa.
In this study, two polyethylene covered tunnels having open-ended naturally-ventilation system (NVT) and a fan-pad evaporative cooling system (FPCT) were compared in terms of inside microclimatic conditions.
Temperature and RH were monitored from the 6^th May 2013 to the 23^rd June 2013. Two butter-head lettuce cultivars, ‘Ballerina’ and ‘Nadine’ were used to determine the effects of two microclimates on crop growth, yield and quality.
The results indicated that daytime temperature inside the tunnels was between 4 and 10°C higher than outside.
The air temperature in the NVT was between 4 and 6°C higher than in the FPCT. RH was extremely low in the NVT, but was within the crop optima for most crops, including lettuce in the FPCT. The high temperatures in the NVT did not negatively influence the growth of the lettuce.
The growth of the cultivar ‘Ballerina’ was faster than ‘Nadine’ under both microclimates.
The yield of ‘Ballerina’ was enhanced by the optimum environmental conditions provided by the FPCT, but the cultivar was more susceptible to leaf tip-burn, which was more prevalent under the FPCT conditions, compared to the NVT conditions.
With the right choice of cultivar, the NVT could be used during winter for lettuce production.

XXX International Horticultural Congress IHC2018: III International Symposium on Innovation and New Technologies in Protected Cultivation

E.L. Thipe, T.S. Workneh, A.O. Odindo, M.D. Laing

natural ventilation, fan-pad evaporative cooling, temperature, RH

https://doi.org/10.17660/ActaHortic.2020.1271.3