Green Manure Species for Phytoremediation of Soil With Tebuthiuron and Vinasse.

Luziane Cristina Ferreira,Rafael Simões Tomaz,Jaqueline Matos Cruz,Bruno Rafael De Almeida Moreira,Paulo Renato Matos Lopes,Ederio Dino Bidoia,Renato Nallin Montagnolli,Evandro Pereira Prado,Yanca Araujo Frias,Ronaldo Da Silva Viana

doi:10.3389/fbioe.2020.613642

Abstract

Tebuthiuron is often used to control weed growth in sugarcane cultures. This herbicide is highly toxic and can persist in soil for up to 2 years according to its degradation half-life. Hence, its residual effect is highly hazardous for the environment and local habitants via leaching, surface runoff. Screening out of species of green manure as potential phytoremediators for tebuthiuron in soil, with and with no vinasse, accordingly is the scientific point of this study. Green manure species selected for the trial in greenhouse were jack bean [Canavalia ensiformis (L.) DC.], pigeon pea [Cajanus cajan (L. Millsp.)], velvet bean [Mucuna pruriens (L.) DC.)], and millet [Pennisetum glaucum (L.) R.Br.], and Crotalaria juncea L. as bioindicator of this herbicide. The determination/quantification of height, stem diameter, and number of leaves in all plants were monitored, as well as other morphological traits for drafting any inference on biomass production. Moreover, ecotoxicity bioassays were performed from soil samples at the beginning and at the end of the experiment. Results showed preliminary evidence of effective phytoremediation capacity by M. pruriens and P. glaucum in soils with tebuthiuron, as the growth of C. juncea was sustained. Both Gompertz approach and principal component analysis predicted that these green manure species could grow healthier and for longer periods in soils containing tebuthiuron and vinasse and, thus, reduce physiological anomalies due to ecotoxicity. The implications of this study may aid in the implementation of cost-effective strategies targeting decontamination of tebuthiuron in sugarcane crops with vinasse application in fertigation.

Highlights

Sugarcane is affected by weeds, despite its highly efficient photosynthetic pathway (C4) that promotes adequate development, especially in its early stages
We argue that it is imperative to evaluate the ecotoxicological potential in a broader time-dependent approach to demonstrate the success of bioremediation strategies (Banks and Schultz, 2005)
As long as the manuring by fertilizing agents is effective in remediating the soil, the less probable tebuthiuron persists at high concentrations in soil and, becoming harmful to non-target organisms as shown in ecotoxicity bioassays

Summary

Introduction

Sugarcane is affected by weeds, despite its highly efficient photosynthetic pathway (C4) that promotes adequate development, especially in its early stages. The planting of sugarcane takes place in wide open areas so that high productivity is achieved, aided by technological tools for the proper weed management as herbicides (Kuva et al, 2008; Oliveira and Brighenti, 2011). Such chemical method is the first choice of agricultural producers due to its ease of access, availability, and low operational costs, compared to other control techniques (Kuva et al, 2008). Successive applications without proper management can make its potential for impact even greater on soil and groundwater (Christofoletti et al, 2017)

Methods

Results

Conclusion