ISHS Acta Horticulturae 156: XII Working Party on Greenhouse Cucumbers
EFFECT OF SOIL TEMPERATURE ON GROWTH OF CUCUMBER IN DIFFERENT AIR TEMPERATURE AND RADIATION REGIME - POSTER |
| Authors: | H. Krug, F. Thiel |
| Abstract:
In model experiments (s. Krug and Liebig, 1979a + b, 1984) using temperature controlled beds (figure 1) in greenhouses with different set points for the heating unit of the air, the effect of soil temperature, air temperature, irradiance and ontogenetic growth and their interactions on wilting, vegetative growth, and yielding of cucumber plants (c.v. 'Pepinex 69') were investigated. Ontogenesis was regarded by the growth phases. 1.: one week after planting, 2.: one week after planting to anthesis at the 8th node, 3.: following growth. Wilting was valued by grades from 0 (fully turgescent) to 4 (strong) wilting. Soil temperatures causing wilting ≥ 1 were 16° C during the 1. phase, close below 16° C during the 2. and 3. phase in spring and autumn and close below 14° C during the 2. phase and at 12° C during the 3. phase in summer (figure 2). There was no significant effect of air temperature caused by heating. Sensibility increased with short term high irradiance in winter, but decreased with long term high irradiance (and higher temperatures) in summer. Moreover sensibility decreased with ontogenesis. Length growth of the stems was significantly promoted by higher soil temperature (up to 23° C) only during the 1. phase (figure 3). Leaf growth was promoted by higher soil temperature during the 1. and 2. phase, especially in combination with high irradiance and high air temperature (figure 4). In the 3. phase there was no significant reaction to soil temperature. Low soil temperature causing wilting during the 1. phase showed a long term retartation of stem and leaf growth (table 1). Start of harvest (1 kg fruits) was earlier with higher air temperature (checked up to 23° C) and delayed by low soil temperature which caused wilting during the 1. phase (figure 5). Yield of stem fruits was increased by soil temperature increasing from 16 to 18° C, especially of those cucumbers planted in winter (figure 6). Market quality was not significantly effected by soil temperature (15 – 25° C). To calculate uncritical planting dates air temperatures depending on set points of the heating unit (model of Damrath, 1980) and corresponding soil temperatures were computed (figure 7). Granting that soil temperature does not drop below 18° C during the 1. phase and below 16° C during the 2 and 3 the uncritical period starts
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