Possibilities for soilless cultivation in cut chrysanthemum: Effect of irrigation frequencies and spacing schedules

Three levels of irrigation frequencies, provided by root misting, combined with three plant densities and two spacing treatments were tested to evaluate the optimum conditions during the first crop stages of chrysanthemum in a soilless cultivation system (aeroponics) in an experiment conducted in autumn. The optimum misting frequency was 3¿2’ times ¿ min h-1. A higher frequency (12¿1’) had no additional effect, whereas the lowest frequency (1¿6’) had a negative effect on total shoot dry mass (TDMs). The highest plant densities (172 and 344 plants m-2) could be used until week 2 with hardly any negative effect on TDMs, and resulted in higher light interception and higher total shoot dry mass per m2. During the period between week 2 and 4 after planting, a higher density (172 compared to 86 plants m-2) had a strong negative impact on the TDMs, while a further increase to 344 plants m-2 had only a minor effect. When spacing (week 2) from 344 to 172 plants m-2, TDMs at week 4 was not negatively affected by the high starting density, though spacing from 172 to 86 plants m-2 resulted in a 13% reduced TDMs, as compared to plants grown at 86 plants m-2 continuously. It is concluded that the irrigation frequency until week 4 after planting under these light conditions, should be three times per hour. Furthermore, very high plant densities (e.g., 344 plants m-2) are feasible until week 2 with hardly any negative effects on plant growth, while spacing schemes give several possibilities for a smaller reduction of the TDMs, than that expected by the higher initial densities.