Rice cultivation in former rubber land without soil remediation contribute toxicity risk of heritable heavy metals contamination

Abstract

The rubber-based intercropping management system (RBIS) land management using chemical fertilizer and herbicides cause heavy metal accumulation in soil. Rice is a good heavy metal bioindicator to monitor soil quality and often integrated with RBIS while rubber trees are young as subsistence farming. Heavy metal accumulation in soil and hill paddy grown on former rubber land and specialized paddy field (control) had been assessed to determine whether harvested rice grain poses toxicity risk. Grain harvested from specialized paddy land was safer to consume as none of the selected heavy metal concentrations in rice grain had exceeded the permissible limit of Malaysia Food Regulation 1985 (MFR 1985). Meanwhile, hill paddy grown intercropping with young rubber trees on former rubber land had accumulated a high amount of heavy metals in rice grain whereby nonessential heavy metals like arsenic, cadmium and lead had exceeded the permissible limit of MFR 1985. Commonly, indigenous hill paddy belongs to tall paddy variety group can grow more than 120 cm tall. All harvested hill paddy landraces grown on specialized paddy field surpassed 120 cm. Nevertheless, all hill paddy landraces that were cultivated in former rubber land were below 100 cm tall indicated that heavy metal phytotoxicity occurred in plants. Rice grain produced in former rubber land poses toxicity risk to consumers due to unsustainable conventional agricultural management practice. Soil degradation needs to be prevented as it can impact food safety and food security. Further soil remediation requirement must be determined to ensure high productivity and safety.