Effective Control against Broadleaf Weed Species Provided by Biodegradable PBAT/PLA Mulch Film Embedded with the Herbicide 2-Methyl-4-Chlorophenoxyacetic Acid (MCPA).

Habib Khan,Iza Radecka,Guozhan Jiang,Grażyna Adamus,Timothy C Baldwin,Sharanjit Kaur,Inna Bretz,Khadar Duale,Marek Kowalczuk

doi:10.1021/acssuschemeng.0c00991

Abstract

Biodegradable mulches are considered a promising alternative to polyethylene-based, nonbiodegradable mulch for sustainable agriculture. In the present study, a bioactive 2-methyl-4- cholorophenoxyacetic acid/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (MCPA-PHBV) conjugate blended with biodegradable poly(butylene adipate-co-terephthalate/polylactide (PBAT/PLA) was developed and used as mulch under controlled condition greenhouse pot experiment with fava bean (Vicia faba) as the nontarget crop species. The objectives were to examine the effectiveness of sustained-release of MCPA herbicide from biodegradable mulch for broadleaf weed suppression and to assess any adverse effects of the herbicide on the nontarget species (fava bean). The energy-dispersive X-ray spectroscopy analysis (EDS) suggests that a substantial quantity of the herbicide was released from the biodegradable mulch which effectively killed the broadleaf weed species even at 1% MCPA concentration. However, the higher concentrations of the herbicide adversely affected several physiological parameters of fava bean growth and development. Stomatal conductance decreased, while leaf temperature subsequently rose (at MCPA concentrations 5, 7.5, and 10%). The quantum yield of the Photosystem II (PSII) indicates that the photosynthetic efficiency was also restricted at concentrations 7.5% and 10%. Evidently, this slow-release herbicide system worked efficiently for broadleaf weed control but at higher concentrations, resulted in adverse physiological effects on the nontarget crop species. This study has demonstrated that biodegradable mulches containing MCPA herbicide are able to effectively inhibit the growth of broad leaf weed species and may be of potential importance in a wide variety of horticultural and agricultural applications.

Highlights

Agricultural mulches are used worldwide to control weeds, alter soil temperature, and conserve soil moisture, which subsequently improves both the yield and quality of food crops.[1−3] mulching material helps to protect delicate crop species from unfavorable biotic and abiotic stress conditions, resulting from extreme weather, insects, and weeds
Data on the weed population recorded 3 weeks after the planting of the fava beans indicated that the soil used in the greenhouse pot experiment was heavily infested predominantly with seeds of broadleaf weeds (Table 2)
The weed population counted at the time of bioactive mulch film application demonstrated nonsignificant statistical differences in weed numbers between the experimental treatments, which is an important point to determine the validity of the present study on weed infestation and suppression caused by the MCPA-PHBV bioactive film (Table 2)

Summary

Introduction

Agricultural mulches are used worldwide to control weeds, alter soil temperature, and conserve soil moisture, which subsequently improves both the yield and quality of food crops.[1−3] mulching material helps to protect delicate crop species from unfavorable biotic and abiotic stress conditions, resulting from extreme weather, insects, and weeds. The commercial use of plastic mulches, mainly for vegetable production, started in the early 1960s.4. These plastic products included polyethylene (PE), polyvinyl chloride, and ethylene vinyl acetate, Most of which have been produced from petroleum-based plastics, usually PE polymers, which are nonbiodegradable.[4]. The global application of plastic films for use in greenhouses and mulching was expected to grow by 69% from 4.4 million tons in 2012 to 7.4 million tons in 2019.5 the use of PE film in agriculture often entails environmental problems, because it comprises high molecular weight molecules with hydrophobic properties. The degradation of polyethylene mulch in the soil may lead to the formation of environmentally harmful chemical products, such as aldehydes and ketones.[6] Due to high chemical stability, polyethylene requires about 100 years for its complete decomposition.[1]

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