Strawberry Living Mulch in an Organic Vineyard

A living mulch system can provide beneficial biodiversified phytocoenoses and spatial competition against weeds; however, it may also compete for water with the main cultivated crop under Mediterranean climate conditions. Strawberries employed as living mulch in a rain-fed hill vineyard of central Italy were evaluated for two years through a participative approach involving the farmer. A local wild strawberry was propagated by stolons to obtain small plantlets easily uprooted after the summer and then transplanted to a one-year-old vineyard. The densities of two and four strawberry plants per grapevine were compared with no living mulch in a randomized complete block design. A horizontal blade weeder was used once a year in all treatments. The results showed that strawberries as living mulch plus application of a blade weeder avoided the need for further soil tillage and assured a full soil cover during winter for both initial planting densities. The strawberry living mulch did not alter the grapevine transpiration during an incident of water stress in summer. Moreover, the yield per vine and the grape quality were comparable with those of the soil without living mulch. The growth of strawberry mulch was relevant in the area surrounding the vines. Furthermore, the living mulch guaranteed a constant soil cover reducing the risk for soil erosion while increasing the vineyard’s biological diversity. This may imply a higher resilience.

Integrated management of living mulches for weed control: A review

Living mulches are cover crops grown simultaneously with and in close proximity to cash crops. Advantages of living mulches over killed cover crops may include increased weed suppression, erosion and leaching control, soil health, and resource-use efficiency. Advantages of living mulches over synthetic mulches may include enhanced agroecosystem biodiversity and suitability for a wider range of cropping systems. A major disadvantage of this practice is the potential for competition between living mulches and cash crops. The intensity and outcome of mulch-crop competition depend on agroecosystem management as well as climate and other factors. In this review, we consider the management of living mulches for weed control in field and vegetable cropping systems of temperate environments. More than 50 years of research have demonstrated that mechanical or chemical suppression of a living mulch can limit mulch-crop competition without killing the mulch and thereby losing its benefits. Such tactics can also contribute to weed suppression. Mechanical and chemical regulation should be combined with cultural practices that give the main crop a competitive advantage over the living mulch, which in turn outcompetes the weeds. Promising approaches include crop and mulch cultivar selection, changes to planting time, density, and planting pattern, and changes to fertilization or irrigation regimes. A systems approach to living mulch management, including an increased emphasis on the interactions between management methods, may increase the benefits and lower the risks associated with this practice.

Establishing white clover (Trifolium repens) as a living mulch: weed control and herbicide tolerance

With the increasing focus on herbicide-resistant weeds and the lack of introduction of new modes of action, many producers have turned to annual cover crops as a tool for reducing weed populations. Recent studies have suggested that perennial cover crops such as white clover could be used as living mulch. However, white clover is slow to establish and is susceptible to competition from winter weeds. Therefore, the objective of this study was to determine clover tolerance and weed control in established stands of white clover to several herbicides. Studies were conducted in the fall and winter of 2018 to 2019 and 2019 to 2020 at the J. Phil Campbell Research and Education Center in Watkinsville, GA, and the Southeast Georgia Research and Education Center in Midville, GA. POST applications of imazethapyr, bentazon, or flumetsulam at low and high rates, or in combination with 2,4-D and 2,4-DB, were applied when clover reached 2 to 3 trifoliate stage. Six weeks after the initial POST application, a sequential application of bentazon and flumetsulam individually, and combinations of 2,4-D, 2,4-DB, and flumetsulam were applied over designated plots. Clover biomass was similar across all treatments except where it was reduced by sequential applications of 2,4-D + 2,4-DB + flumetsulam in the 2019 to 2020 season indicating that most treatments were safe for use on establishing living mulch clover. A single application of flumetsulam at the low rate or a single application of 2,4-D + 2,4-DB provided the greatest control of all weed species while minimizing clover injury when compared to the non-treated check. These herbicide options allow for control of problematic winter weeds during clover establishment, maximizing clover biomass and limiting canopy gaps that would allow for summer weed emergence.

Significance of herbicide order in sequential applications to target weeds in a sunn hemp living mulch

Striking a balance between the weed control capacity of living mulches and their competition with the main crop is complex. At rates that avoid severe injury to living mulch, herbicides may reduce their vigor while simultaneously contributing towards weed control. In a two-year field study carried out in Freeville, NY, USA, we evaluated the effects of various combinations consisting of two herbicides, applied sequentially at reduced rates, on the growth of a sunn hemp living mulch and weeds (including common lambsquarters, common purslane, hairy galinsoga, and Powell amaranth). When a herbicide with primarily POST activity (Type 1) (e.g., rimsulfuron, 0.005 to 0.007 kg ai ha-1) was applied first, performance of sunn hemp (1.7 to 3.9 tons ha-1 dry biomass; 10 to 88% groundcover) was poor and weed growth (25 to 62% groundcover) was high, likely because sunn hemp, severely injured at a young growth stage, was outcompeted by weeds. A follow-up application (approximately two weeks later) of a herbicide with primarily PRE and residual activities (Type 2) (e.g., metribuzin, 0.05 to 0.15 kg ai ha-1), with a surfactant to enhance its POST activity, had little effect on established weeds. However, because sunn hemp was already 20 cm tall at weed emergence, applying a Type 2 herbicide first, did not cause severe injury to sunn hemp and reduced weed pressure, thereby also enhancing sunn hemp performance (3.8 to 6.1 tons ha-1 dry biomass; 85 to 94% groundcover). Moreover, the follow-up application of a Type 1 herbicide affected the smaller weeds more (4 to 21% groundcover) than the better-established sunn hemp. Our results demonstrate that an appropriate sequence of herbicides at reduced rates may be important to control weeds while maintaining a healthy living mulch stand.

Weed Suppression Potential of Living Mulches, Newspaper Hydromulches, and Compost Blankets in Organically Managed Carrot Production

Direct seeding into strip-tilled zones (STZs) of living mulches may require weed suppression tactics for soil surfaces exposed within the STZ. Three surface mulch options (hydromulch, compost blanket, and a no-mulch control) were evaluated for their ability to suppress weeds and improve crop performance when applied in STZs seeded to carrot (Daucus carota). These STZs were located within one of five living mulch options [red clover (Trifolium pratense), white clover (Trifolium repens), perennial ryegrass (Lolium perenne), a weed-free control, and a weedy control]. From measurements spanning 2 years at two North Dakota locations, dry weed biomass was lower in STZs where hydromulch or compost blankets were applied compared with the no-mulch control (12, 13, and 82 g·m−2, respectively). The presence of a living mulch adjacent to the STZ reduced carrot root biomass by 49% to 84% compared with the weed-free control. Further research should 1) investigate methods for reducing yield loss from living mulches, and 2) develop biodegradable alternatives to plastic mulches.