Variable impact of rice (Oryza sativa) on soil metal reduction and availability of pore water Fe²⁺ and Mn²⁺ throughout the growth period

ABSTRACT

Flooding of wetland or agricultural soils can result in substantial alteration of the pore water trace metal profiles and potentially also influence the bioavailability of other trace elements adsorbed to the insoluble oxides. Experimental microcosms were used to quantify the impact of rice (Oryza sativa) plants across an entire growing cycle on the concentrations of Mn²⁺ and Fe²⁺ in two soil types (red sodosol and grey vertosol). Two water management treatments were included: a standard flooded treatment and a saturated treatment (−3 kPa). Soil pore water profiles were established from samples collected at four sampling depths (2.5, 7.5, 15 and 25 cm) on 50 occasions. Fe²⁺ and Mn²⁺ concentrations were higher in flooded soil than in saturated soil and greatest at a depth of 7.5 cm. The presence of rice plants increased Mn²⁺ concentrations in flooded soils, but tended to decrease Mn²⁺ concentrations in saturated soils. The influence of rice plants on Fe²⁺ concentrations was greatest at a depth of 7.5 cm. Changes in soil pore water Fe²⁺ and Mn²⁺ concentrations due to the presence of rice plants were correlated with flowering and reproduction.

KEYWORDS:

• Manganese
• iron
• flooded soil
• saturated soil
• reducing conditions
• rice
• bioavailability

Acknowledgements

Dr Mark Conyers (Principal Research Scientist, DPI, Wagga Wagga) and Dr Geoff Beecher (Research Agronomist, DPI, Yanco) are acknowledged for accessing their facilities and technical supports.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

K. M. Shamsul Haque http://orcid.org/0000-0001-5927-9649

Additional information

Funding

This work is supported by Charles Sturt University Postgraduate Research Scholarship to the School of Agriculture and Wine Sciences.