A recirculating resin‐buffered hydroponic system for controlling nutrient ion activities

Abstract

A recirculating resin‐buffered hydroponic system was developed to control the activities of nutrient ions in solution at concentrations similar to those found in soil solution. The recirculating hydroponic system was designed to supply adequate buffering and timely replenishment of nutrients during the course of long‐term experiments. Nutrient solution was recharged by circulating it through columns of ion exchange and chelating resins before its return to plant culture vessels. The recirculating resin‐buffered system consisted of four different types of ion exchange and chelating resins housed in separate columns: strong‐acid resin to buffer Ca, Mg, K and Mn in solution; weak‐acid resin to buffer pH; partially‐neutralized Al on strong‐acid resin to buffer P in solution; and chelating resin to buffer Zn, Cu, Mn, and Ni and to supply Fe to EDDHA in solution. Control of nutrients and pH was begun at the time of seed germination.

The recirculating resin‐buffered system was especially designed to limit Ni contamination in studies of the essentiality of Ni in higher plants. Concentrations of Ni²⁺ in solution were successfully maintained at treatment levels that differed by four orders of magnitude, with the lowest level < 10¹⁴ M. The exchange resins maintained the supply and activities of other nutrients at levels sufficient for the growth of plants. Tomato plants (Lycopersicon esculentum Mill., cv. Wisconsin 55) were successfully grown for six weeks without discarding the nutrient solution in which the plants grew. The pH of recirculating nutrient solutions was well maintained throughout the study. Guard columns protected the primary resin columns from plugging and were replaced during the course of this study to restore flow rates of the nutrient solutions. Maintenance of flow rates, in conjunction with successful reloading of resins with nutrients, assures the feasibility of even longer term plant culture experiments.

Notes

Contribution of the USDA Agricultural Research Service, and the Department of Soil, Crop, and Atmospheric Sciences, Cornell University (Paper No. 1710). This research was part of the program of the Center for Root‐Soil Research.

Current address of senior author: Chemical Research Development & Engineering Center, Attn: SMCCR‐RST‐E, Aberdeen Proving Ground, MD 21010.