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There is evidence in the literature that decreasing soil moisture content is associated with increases in the osmotic pressure of the tissue fluids in both roots and tops of plants (26,27), decreases in rate of vegetative growth (1,9,15,30, 64), modifications in stomatal opening (16, 17), a depletion in starch reserves (15,35,52, 64), a decrease in apparent photosynthesis, and an increase in respiration (50). Many of these effects were noted even though the respective plants did not wilt, and notwithstanding the fact that there is considerable evidence (8, 24, 58, 62)

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IntroductionMany western farmers believe that soil alkali is more detrimental to crop growth during the hot weather than during the cooler seasons of the year. Other agricultural workers have noted that damage to crops due to alkali (soil salinity) is more serious in the hot interior valleys than along the coast where the climate is more moderable. It is not definitely known whether or not soil salinity concentrations are comparable between different seasons of the year or between respective areas. Yet, information on this question is pertinent to the development of management practices which would aid in ameliorating soil salinity conditions at different seasons of the year and under different climatic conditions.In order to obtain definite information on this question, Southern California is shown in figure 1. In spite of the diversity of climates the three locations were so near each other that the work could be adequately supervised and coordinated from Riverside. The stations were also in the same approximate latitude so that length of day was essentially the same at all three.The sand culture tanks have been described by EATON (4) solution drained through the sand to the reservoir below. The sand contained 0.2 per cent. magnetite to provide the iron needed by crops as suggested by CHAPMAN (2). The composition of the culture solutions used in 1941 is given in table I. They were maintained at about pH 6.5.The salts used in making up these solutions were carefully selected for low contents of boron and heavy metals.Growth responses obtained in these culture solutions are believed to be qualitatively characteristic of plant growth in soil solutions of equal salt content, but it should be borne in mind that drainage, aeration, nutrient