Growth and nutrition of rice seedlings when phosphorus or silicon was applied to a soil heavily contaminated with both arsenic and cadmium

Abstract

There is a lack of affordable and effective strategies to mitigate multiple heavy metal contamination in lowland rice production. We tested phosphorus (P) or silicon (Si) addition to a soil contaminated with both arsenic (As) and cadmium (Cd) for their mitigation potential in rice seedlings. Rice variety IR64 was grown in pots with either P (0, 2.5, 5, 10, 20 (recommended rate), 40 and 80 mg P kg⁻¹ soil), or Si (0, 0.15, 0.3, 0.6, 1.2 and 2.4 g Si kg⁻¹ soil) addition until the end of tillering phase (nine weeks). Over this period, growth of rice was enhanced by up to 35% with the addition of P until the recommended rate, whereas growth was reduced beyond 0.3 g Si kg⁻¹ application. Photosynthetic rate and maximum PSII quantum yield of the youngest fully expanded leaves were similar among P and Si treatments. Phosphorus addition increased shoot [As] and decreased shoot [Cd] by up to 59% and 63%, respectively, and both effects were visible only after plants reached P sufficiency. Silicon addition from 0 to 2.4 mg Si kg⁻¹ soil increased shoot [As] by up to 28% and decreased [Cd] by up to 25%. Accumulation of As and Cd in the leaves from top to bottom of the canopy increased by factors of 10 and 7.6, respectively. Therefore, P or Si application cannot generally be recommended as remedy for rice production on multiple heavy metal contaminated soil. However, rice plants have efficient mechanisms to translocate As and Cd to mature leaves.

Keywords:

• bioavailability
• mitigation
• paddy rice
• remediation
• toxicity

Author’s contributions

LS, MT and KD designed the experiment and wrote the manuscript, and LS and MT conducted the experiment.

Data availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Additional information

Funding

This work was supported by the Georg Forster Research Fellowship of the Alexander von Humboldt Foundation under the Humboldt ID: 1164603 received to the first author. Authors acknowledge the technical support of Marlies Niebuhr and Kirsten Fladung of the Section of Plant Nutrition and Crop Physiology, Department of Crop Sciences, University of Göttingen. Authors are also thankful for very helpful comments by JK Vidanarachchi to an earlier version of the manuscript.