Utilization of plant material for remediation of herbicide-contaminated soils

Biostimulation is a successful method for remediation of soils and other matrices contaminated with a wide range of xenobiotics. Use of the appropriate soil amendments can enhance the biodegrading potential of indigenous soil microbial populations. Plant materials have been studied by others as biostimulating amendments for soils contaminated with a wide range of herbicides. Our previous studies indicated that annual ryegrass (Lolium multiforum L.) residue was the most effective amendment for enhancing cyanazine (2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2yl]amino]-2 methyl- propanenitrile) and fluometuron (N,N-dimethyl-N'-[trifluoromethyl)-phenyl]urea) degradation in soils. Thus we pursued a comparative study of various crop residues on the degradation of fluometuron in soil. In this study we investigated the effects of amending soil with hairy vetch (Viciavillosa Roth), rice (Oryza sativa L.), or ryegrass residues on the degradation of a high concentration (500 mole kg(-1) soil) of fluometuron (technical grade or commercial formulation). Initially, all three amendments enhanced fluometuron degradation in soil treated with technical material or commercial formulation. Hairy vetch transiently enhanced degradation, while the two grass residues stimulated degradation during the entire study (60 d). Rice straw had the greatest stimulation. In short term studies (21 d), ryegrass had the greatest effect on stimulating soil bacterial populations and several enzyme activities. Use of the appropriate plant residue is a promising approach for enhancing the remediation of herbicide-contaminated soils.