Improvement of Utilization Efficiency and Ion Balance of Recycled Nutrient Solution in Closed Soilless Culture of Paprika (Capsicum annuum L.)

Abstract

Improvement of Utilization Efficiency and Ion Balance of Recycled Nutrient Solution in Closed Soilless Culture of Paprika (Capsicum annuum L.)

Myat Thaint Ko Department of Plant Science Graduate School of Seoul National University

ABSTRACT Although closed soilless culture is useful for saving water and fertilizers with minimizing environmental pollution, adequate management of nutrient solutions is still not stabilized in greenhouse cultivation. However, ion imbalance in recycled nutrient solution and the accumulation of nutrients in root medium are serious problems affecting plant growth. For efficient nutrient management, an adjustment of the recycled nutrient solution at an appropriate analysis interval is required considering the nutrient and water demands of plants. The aims of this study are to compare the ion balance, yield, and use of water and fertilizers between the closed and open soilless culture systems, to find out the proper renewal period reducing ion imbalance in the recycled nutrient solution, to investigate the nutrient and water uptake and the yield and mineral contents of the plants by the renewal period of recycled nutrient solution, and to determine the effect of renewal pattern on ion balance in the recycled nutrient solution and substrate, and nutrient uptake of paprika plants. Yield reduction by 19% was observed in the closed system compared with that in the open system after four harvests. Water use efficiency (WUE) and fertilizer use efficiency (FUE) were 68% and 78% higher in the closed system than those in the open system. The ion imbalance in the recycled nutrient solution appeared after 4 weeks even though the EC and pH were maintained within acceptable ranges. Among the different renewal periods, the changes in cation and anion ratios in the recycled nutrient solution could be reduced by renewing every 4 weeks. Although 50 to 51% WUE and 61 to 67% FUE were higher in the closed system using different renewal periods than those in the open system, the lowest fruit yield was observed in the closed system at a 12-week renewal period. Considering nutrient balance and yield, an adequate renewal period of the recycled nutrient solution was suggested as 4 weeks, but it can be extended to 8 weeks practically. The ion balances change in the recycled nutrient solution was reduced at the renewal pattern of 4-4-4 weeks, and followed by 6-4-2 and 8-2-2 weeks. Particularly the accumulation of Ca2+ and Mg2+ was reduced as the same trend as above. No significant differences in nutrient uptake, yield and plant growth were observed among all the renewal patterns. Chemical analysis indicated that paprika needs less Ca and Mg in the fruits than in the leaves during fruit growth. It can be concluded that renewal period and pattern play important roles in the ion balances of the recycled nutrient solution and root medium and the uptakes of water and nutrients by plants in closed soilless culture. For more efficient management of nutrient solution in closed soilless culture, adjustment (or renewal) of recycled nutrient solution considering growing stage and environmental conditions are required as further study.

Key words: closed rockwool culture, ion imbalance, recycled nutrient solution, renewal period, water and nutrient uptake,

Student Number: 2010-31333