Effect of Chelates vs. Ionic Salts of Microelements and Nitrogen Form on Hydroponic Solution pH

Abstract

Microelements are supplied at low concentrations, yet have a profound effect on plant growth. These experiments explore the role of their chemical form and that of nitrogen on plant uptake. Chrysanthemum × morifolium cv. Bright Golden Anne, which is sensitive to ammonium, was the test plant. There were four hydroponic treatments with nitrogen supplied at 200 ppm as either 100% nitrate or 25:75 ammonium to nitrate. Micronutrients were supplied either in the chelate or ionic salt form. All other macro cations and anions were the same concentration. All solutions were allowed to stand for 24 h and then adjusted to pH 5.9–6.0. Once the plants were set into the solution they were allowed to adjust for 1 h before the pH was measured hourly for 24 h and then measured 4 times per day for 14 days. As expected both solutions of 100% showed an increase in pH from 6.2 and 7.1 within 5 h. As expected, the pH of the 25:75 ammonium:nitrate, with micronutrients as ionic salts decreased from 5.8 to 5.2, while the chelate solution was stable between 5.8 and 6.3. During the entire time course there was a daily oscillation within each pH range for the nitrate-based solutions.

Keywords:

• Ammonium
• Ammonia
• Chrysanthemum
• Nitrate

Acknowledgments

This research supported by plant material from Yoder Brothers, Inc. This article submitted as Nebraska Agriculture Research Division journal series number 14036.