Growth of Chrysanthemum at Low, Relatively Steady Nutrient Levels in a Commercial-style Substrate

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Nutrient solution with a molar ratio of 10 N: 1 P: 3 K was applied in scheduled intervals at rates of 0.5, 1, 4, or 20 mm N (NO3 + NH4) to Dendranthema ×grandiflorum (Ramat.) Kitamura `Sunny Mandalay' plants seven (7/day) or 14 times/day (14/day). These plants were compared to a 20 mm N control in which nutrient solution was applied when the soil moisture tension reached 30 kPa. Plants with 7/day had significant quadratic relationships for height, width, and dry weight, with the lowest responses at the low nutrient concentration. With 14/day, height and dry weight did not differ, although width did increase linearly with nutrient solution concentration. However, linear regression slopes for all three variables were much lower with 1Vday than with 7/day. At midcrop in both experiments, significant regression curves indicated that the lower concentrations of nutrient solution resulted in lower tissue N and K levels; however, slopes of the linear regressions were lower with 14/day than with 7/day. With 7/day, the water content (percentage) of plants in the schedule-fertilized treatments was higher in plants receiving higher nutrient concentrations, as indicated by the significant linear and quadratic regression curves. With 14/day, the water content was linearly related to solution nutrient concentration, but with a lower slope than with 7/day. These three trends indicate that steady-state nutrition was more closely achieved in a commercial-style substrate with 14/day applications of nutrient solution. These results suggest that plant growth that meets commercial expectations can be achieved at lower soil solution nutrient concentrations than currently applied.