Growth Response of Chrysanthemum to Various Container Medium Moisture Tension Levels

Abstract

A computer-controlled drip irrigation system was used to implement three types of moisture regimes in the potting medium of container-grown chrysanthemum [Dendranthema × grandiflorum (Ramat.) Kitamura] plants: “constant” moisture tension treatments were maintained by setting low- and high-tension set-points to the same value; “variable” tension treatments were imposed by setting the low- and high-tension set-points to 2 and 7 kPa, respectively, “timed” irrigation consisted of irrigating once per day for a fixed (excessive) duration that resulted in fluctuations in tension ranging from O to 10 kPa. Constant moisture tension conditions in the range of 0.8 to 16 kPa showed decreasing fresh and dry weight patterns with increasing tension, decreasing average moisture content, decreasing amounts of applied irrigation solution, and, consequently, with decreasing amounts of nutrients applied. Plants grown under conditions where the moisture content fluctuated appreciably (variable and timed) tended to be larger than those grown within the narrow tension ranges (constant); for the latter, optimal plant growth occurred at the lowest tension (0.8 kpa) and highest average moisture content (71%). For fluctuating conditions, the control (with the widest fluctuations) had the highest dry weight growth. The variable tension treatments, while resulting in average moisture tensions of 4.4 to 4.9 kpa, resulted in plant growth similar to plants grown at constant low tension (0.8 to 1.6 kPa), rather than those grown at tensions between 4 and 5 kPa.