SOIL WARMING BY WASTE WATER OF IRIS HOLLANDICA CROPS CULTIVATED UNDER PLASTIC TUNNELS : THERMIC AND AGRONOMIC ASPECT.

T. Boulard, A. Mesvel, A. Baille
With the increase of energy cost, the use of low temperature waste water for soil warming in protective horticulture could be profitable. In this study, waste water at 30° C is used to heat eight different iris-crops cultivated under plastic tunnels, by mean of a soil-air heating system. This system is compared with a standard pulsed-air heating system, on both thermic and agronomic aspects.

Air temperature at 50 cm can be maintained the same in the two tunnels, with a gain of about 5°C on soil temperature at -10 cm in the soil-air heated tunnel. During the night, these temperature levels are obtained with the same energy input, but if we consider the whole day, 10% more energy is dissipated by the soil-air system.

Soil warming accelerates growth and development of leaves, stems and flowers, essentially when the plant is still growing under the soil surface. The resultant reduction of crops and heating duration is on average of 22 days (93 days against 115 days) and the energy saving reaches 45% if we do not take into account the soil warming energy (given by waste water), and 12% if we take it into account.

Boulard, T., Mesvel, A. and Baille, A. (1981). SOIL WARMING BY WASTE WATER OF IRIS HOLLANDICA CROPS CULTIVATED UNDER PLASTIC TUNNELS : THERMIC AND AGRONOMIC ASPECT.. Acta Hortic. 115, 627-636
DOI: 10.17660/ActaHortic.1981.115.70
https://doi.org/10.17660/ActaHortic.1981.115.70

Acta Horticulturae