Shoot and biomass reduction of perennial weeds using hydromulches and physical changes in the mulches

Hydromulch, used primarily for erosion control, is now being studied as a weed control method in perennial crops and public gardens where weed control is especially difficult; the most challenging species are perennials having powerful shoots that emerge from subterranean propagules. In a previous article, we considered rhizome sprouting capacity through three experimental hydromulches based on wheat straw (WS), rice husk (RH) and used mushroom substrate (UMS). Here, we present data for the number of emerged shoots and their biomass to test whether the mulches were able to influence outcomes affecting weed-crop competition. In addition, the mechanical resistance of these hydromulches was characterized in terms of punching stress or resistance, considering two air humidity levels and applying an artificial ageing test (AAT) to simulate an average spring rainfall for Mediterranean areas. All three mulching types were effective in reducing the weed biomass (60-85%) and RH and UMS also the number of shoots (39-64%) of the four tested weed species compared to the non-mulched control. Cyperus rotundus was capable of generating the largest shoot number and biomass, regardless of the mulch treatment. In comparison, all three hydromulches provided a more effective control of Cynodon dactylon, Sorghum halepense and Paspalum dilatatum. Air humidity levels did not cause consistent changes in the physical properties of the hydromulches, while all three showed a weakening after the AAT, more pronounced in UMS than in WS or RH-based mulches, which could compromise the duration of effective weed control. Field trials are envisaged to confirm the duration of the perennial weed control associated with these hydromulches.

Automated summary

Hydromulch, primarily used for erosion control, is being studied as a weed control method. Rice husk and used mushroom substrate hydromulches showed better inhibition on weed growth. The hydromulches may weaken after artificial aging, which could affect weed control effectiveness. Field trials are needed to further verify the duration of weed control.