For stable production of open field vegetables, it is necessary to supply appropriate moisture. In this study, we clarified the influence of water supplied by a subsurface irrigation system with a liner sheet gutter on growth of the above- and below-ground parts of lettuce and spinach. In a field test, water moved rapidly for a horizontal distance of 50 cm from the water supply line. The pF value at a distance of 70 cm fell to the degree that vegetables could be grown. In the cultivation of lettuce and spinach, plants grew at distances of up to 75 and 80 cm from the water supply line, respectively, and it was thus clear that a water supply line spacing of 150 cm or less is appropriate. However, there was variation in the growth of vegetables at different distances from the water supply line, with growth at the 45- and 40-cm points being best for lettuce and spinach, respectively. Roots were the same reaction as above-ground in lettuce, but were different in spinach. Root growth was inhibited at a point with less soil moisture growth of above-ground parts were not suppressed in spinach. This variation will need further investigation for the establishment of a stable production technology in order to carry out efficient moisture management.

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