What levels of soil Mn2+ can pulse and legume crops tolerate when grown in rotation with paddy rice?

Shamsul Haque, Julia Howitt, Mike Dyall-Smith, Leslie Ann Weston, Philip Eberbach

Research output: Contribution to journalArticlepeer-review


Elevated concentrations of manganese (Mn 2+) can persist after drainage in soil following wetland rice production, leading to toxicity in subsequent legume crops. To evaluate Mn 2+ concentration causing adverse impacts on crop establishment and growth, a controlled environment experiment using hydroponics was designed. Germination and growth of field pea, faba bean and mung bean were evaluated over 21 d with an increase in Mn 2+ (0 − 50 mg Mn 2+L −1). Germination of all crops was impacted significantly with an increase in concentration of Mn 2+. Leaf chlorophyll content as well as all plant growth parameters assessed (dry weight, height) were negatively impacted (p < 0.05) by increasing concentrations of Mn 2+. Field peas and faba beans proved more sensitive to Mn 2+ than did mung beans at concentrations of 5 − 10 mg L −1. Field pea and faba bean specifically exhibited reduced height (30 − 60% and 4 − 41%, respectively), root length (12 − 30% and 20 − 25%, respectively), and shoot weight (41 − 69% and 47 − 81%, respectively). Mung bean was less impacted in terms of plant height with 23% reduction at 25 mg Mn 2+ L −1 and shoot dry weight reduced by 48% at 50 mg Mn 2+ L −1. Total chlorophyll content of mung bean was severely affected (86% reduction at 50 mg Mn 2+ L −1), with field pea least impacted. Our findings suggest that significant Mn 2+ toxicity could potentially occur in terms of legume germination and overall growth if legume crops are sown into post-rice soils with ≥5 mg Mn 2+L −1. Soil Mn 2+ level must be considered when developing cropping strategies following flooded rice.
Original languageEnglish
Pages (from-to)1-15
JournalJournal of Plant Nutrition
Publication statusPublished - 2022


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