S08 - Session P3 - Identification of variations in nutrient uptake ratios of Pak Choi as an indicator for ion specific nutrient management potential

Authors: Markus Abel *, Sabine Wittmann, Ivonne Juettner, Heike Mempel

Ion specific nutrient management (ISNM) promises to increase yields and nutrient use efficiency in hydroponic systems by solving the problems of the built-up of specific ions and the deficiency of others, which are liable to occur using the conventional method of controlling EC and pH only. Even though Ion selective electrodes are available, implementation of ISNM in horticultural practice still proves difficult. Previous works have addressed the challenge of decoupled replenishment of individual ions for a limited set of ions, NO 3 , K, and Ca and proposed effective strategies to control the ion interference effect. Nevertheless, implementation of ISNM systems in commercial agricultural operations is still missing, partially due to scarce data on the potential yield and nutrient use benefits. This paper accesses the potential applicability of an ISNM approach for Pak Choi, by closely monitoring ion ratios in two different nutrient solutions under the conventional method of EC and pH adjustment throughout the cultivation period of 21 days by ion chromatography in a Deep-Water Cultivation (DWC) system. Thus, concentration built up and preferential uptake of individual ions will be identified, while EC is to be held constant for all treatments. In a second step, an adapted nutrient recipe to minimize shifts in nutrient ratios will be applied (AR), along with the original recipe (OR). This will give a valuable insight indicating about relevant shifts in the uptake ratios of the monitored ions dependent on the physiological state of the plant and whether the crop qualifies as a potential candidate for dynamic adjustment of ion concentration by ISNM. Differences in dry matter yield between OR and AR can be interpreted as an indication for the yield increase potential of ISNM.