Rhizosphere and green manure effects on soil chemical attributes and metal bioavailability as a function of the distance from plant roots in mono and mixed corn and canola cultures

ABSTRACT

A rhizobox experiment was conducted to study the effects of alfalfa green manure (GM) and the culture system on the dry matter yield and metal uptake in corn (Zea mays) and canola (Brassica napus) grown in rhizobox systems containing a metal-rich agricultural soil. The results showed that GM application increased soil organic matter (SOM), dissolved organic carbon (DOC), and electrical conductivity (EC) by 41%, 82%, and 35%, respectively, while the soil pH decreased by ~0.3 units. These changes were associated with enhanced soil bioavailability of Zn (14%), Cu (26%), and Ni (20%) and improved shoot dry matter yield of the plants. Soil metal bioavailability was also found to be enhanced due to the presence of plant roots. Canola intercropped with corn produced greater individual plant dry weights (IPDWs) of 96% and 59% in the untreated and GM-amended rhizoboxes, respectively. The intercropped corn, however, recorded 25% and 6.4% lower IPDW values in unamended and GM-amended soils, respectively, as compared to the monocropped corn. Enhanced Zn, Cu, and Ni uptakes were observed in canola shoots, while they decreased in corn shoots. The results demonstrate the importance of organic amendment and intercropping strategies for managing metal uptake by plants grown in metal-rich soils.

KEYWORDS:

• Heavy metals
• rhizobox
• organic amendment
• intercropping

Disclosure statement

No potential conflict of interest was reported by the authors.