Salt Tolerance of Sunflower and Lettuce in Cultivated and Uncultivated Grass Soil

We tested two hypotheses: 1) whether a vegetable crop will show greater growth under a given salinity treatment in an uncultivated grass soil than a cultivated soil and 2), if so, whether the greater growth is due to the occasional presence of relatively fresh water in macropores or the interaction between salinity and hypoxia in a soil without significant macropores. A previous study suggested uptake from. macropores was significant only for crops with high root water potential (Emerman and Dawson 1997). Hence, in this study, 21 miniature crops were grown in a greenhouse, and the ratio of root dry weight to transpiration rate was measured as a means of ranking crops in terms of root water potential. Based upon the ranking, \u27Elf’ sunflower (Helianthus annuus L.) was chosen as a crop with relatively high root water potential (ratio = (39 ± 7) mg/(g/day)) and \u27Tom Thumb\u27 lettuce (Lactuca sativa L.) as a crop with relatively low root water potential (rat10 = (0.8 ± 0.3) mg/(g/day)). The miniature cultivars of sunflower and lettuce were grown in a greenhouse in undisturbed cores of salinized, cultivated soil and salinized, uncultivated grass soil, and they were given tap water daily at the plant transpiration rate. There was no significant difference between growth in cultivated and uncultivated grass soil. With the addition of tap water, however, lettuce showed no reduction in growth from the no-salt control at NaCl concentration of 4 g/L. At the same NaCl concentration, mortality was 100% without the addition of cap water. It is suggested that daily irrigation with relatively fresh water in salinized soil may be more successful for crops with low root water potential