Effects of potassium nutrition and water availability on iron toxicity of rice seedlings

Abstract

The aim of the study was to investigate the influence of potassium (K) nutrition and/or aeration of flooded soil through drainage on iron (Fe) toxicity of rice during the period of establishment. A hydroponic experiment with three Fe (0.1, optimal; 1, high; 2.5 mM, very high) and K levels (0.3, low; 2, optimal; 5 mM, high), and a soil experiment with two moisture levels [continuously flooded; alternate-wetting and drying (AWD)] and three Fe levels (16, low; 163, optimal; 490 mg Fe(II) kg⁻¹ soil, high) was conducted. In the hydroponic experiment, high Fe supply increased tissue concentrations of Fe, phosphorus (P) and magnesium (Mg), and reduced manganese (Mn) concentrations. Particularly Fe, K and P were maintained at root surfaces in larger amounts than taken up by the roots. Growth of rice, photosynthesis, maximum quantum yield, effective quantum yield and electron transport rate were decreased at high and very high Fe concentrations while K application had no positive effect. In the soil experiment, growth and nutrient relations under increased Fe supply were similar to those observed in the hydroponic experiment. However, comparing both moisture levels showed that soil solution Fe concentration and plant growth were reduced and tissue P, Mg and Mn concentrations were increased in the AWD system compared to flooding. Therefore, the application of K or aeration of flooded soil cannot be generalized as promising strategies to alleviate Fe toxicity in rice at the initial crop establishment stage.

Keywords:

• chlorophyll fluorescence
• crop establishment
• iron-plaque
• lowland paddy
• photosynthesis

Acknowledgments

We acknowledge the team, particularly the technical assistance of Marlies Niebuhr_, of the Section of Plant Nutrition and Crop Physiology, Department of Crop Sciences, University of Göttingen for their excellent support during experimental work. The effort of H. Meemken, B. Angulo, A. Barreto, Y. Hu, S. Junker, D. Köhler, and H. Schuhknecht is greatly acknowledged.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Georg Forster Research Fellowship of the Alexander von Humboldt Foundation, and K + S Minerals and Agriculture.