Herbicide and Mulch Interactions: A Review of the Literature and Implications for the Landscape Maintenance Industry

Abstract

Use of organic mulch is one of the most common methods of weed control in landscape planting beds and provides other benefits, including improved soil characteristics, increased growth of ornamental plants, and enhanced property aesthetics. In the landscape maintenance industry, it is common to apply mulch and herbicides concurrently to landscape beds to provide long-term, broad-spectrum weed control. It is known that herbicides behave differently when applied to different soil types and organic materials; however, research is lacking concerning which herbicides are most effective with different mulch materials in the landscape. Determining the most effective herbicide–mulch combinations could potentially improve weed control, reduce labor costs from hand weeding, and mitigate negative environmental impacts resulting from off-site herbicide movement. The objective of this paper is to review the research that has been conducted pertaining to various mulch–herbicide combinations in the landscape and in other areas of agricultural production while also identifying key knowledge gaps that should be addressed in future research. Review of the literature suggests satisfactory weed control can be achieved with high mulch depths (≥ 7 cm) regardless of herbicide use, and herbicide–mulch interactions become more pronounced as mulch depth decreases. Additionally, future research is needed to determine which herbicides are best suited for different mulch types to improve weed control and potentially reduce environmental impacts, including herbicide leaching and runoff into urban and suburban waterbodies.

Effects of sorghum residue in presence of pre-emergence herbicides on emergence and biomass of Echinochloa colona and Chloris virgata

“…In such systems, crop residue is retained on the soil surface whereby farmers gain many advantages, such as reduced soil erosion, reduced soil evaporation, increased microorganism activity and reduced weed seed germination [8][9][10]. In conservation agriculture, the application of pre-emergence (PRE) herbicides is highly recommended for the reduction of labor costs, the reduced need for costly post-emergence herbicides and an overall increase in weed suppression and control duration [11][12][13].…”

Allelopathic weed suppression in agroecosystems: A review of theories and practices

“…Satisfactory weed control can be achieved with high mulch depths (> 70 mm) (Marble, 2015). Although the mechanism responsible for weed control is not well understood for all mulch types (Chalker-Scott, 2007), for most weed species, control can be attributed predominantly to light exclusion (Teasdale and Mohler, 2000).…”

“…Although the mechanism responsible for weed control is not well understood for all mulch types (Chalker-Scott, 2007), for most weed species, control can be attributed predominantly to light exclusion (Teasdale and Mohler, 2000). Mulches can also act as a physical barrier to weed germination and growth (Marble, 2015). Certain mulch material, like rye (S. cereale L.), may also control weeds by leaching allelopathic chemicals (Chalker-Scott, 2007).…”

Different Imazethapyr Placements and Rainfall Amounts Affect Phytotoxic Activity of Imazethapyr in Combination with Oil Palm Frond Residue Mulches against Common Weeds in Landscapes

“…Organic mulches have even been shown to reduce emergence and establishment of some of the most troublesome weeds (Marble 2015). Benefits from organic mulches are well established and a wide variety of mulch products are available for landscape use (Chalker-Scott 2007).…”

“…Improved herbicide efficacy was reported from studies where herbicides were sprayed to above, under or a pretreatment on the organic mulch over nursery containers (Chen et al 2013;Somireddy 2012). However, there are no 'herbicide placement' recommendations on pre-emergence herbicide labels in terms of above or under mulch layers (Marble 2015).…”