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Data from: Liquid-applied biodegradable mulches control weeds and protect yield in organic onion production
Summary
Researchers tested a plastic-free alternative for weed control in organic onion farming, made from recycled newspaper mixed with either guar gum or camelina meal. The guar gum version worked nearly as well as traditional plastic mulch at controlling weeds and maintaining onion yields, while fully breaking down in the soil instead of leaving behind plastic fragments. This matters because plastic mulches used in farming can shed microplastics into soil and food crops, so finding effective biodegradable replacements could help reduce a hidden source of microplastic exposure in our food system.
Organic onion production relies on non-biodegradable polyethylene (PE) mulches as a weed control method. Due to plastic pollution, organic horticultural crop growers are searching for environmentally-sound and sustainable biodegradable alternatives to PE mulches. This study aimed to develop cellulose-based biodegradable hydromulches (HMs) for weed suppression and yield improvement in organic onion production. The study was conducted at two sites in North Dakota, Fargo and Absaraka, during the 2023 growing season. Hydromulches were composed of water, shredded recycled newsprint, and one of two tackifiers, guar gum (GG) or camelina meal (CM). The hydromulch treatments include 3% GG, 6% GG, 3% CM, and 6% CM, and were compared to white-on-black PE (1mil) mulch, along with a weed-free and weedy check. Hydromulches were applied to raised bed plots measuring 0.9 x 3.0 meters at a targeted application rate of 5,765 kg dry matter (DM) ha-1. PE mulch provided complete weed suppression at both locations. Among hydromulches, 6% GG showed greater weed suppression (11 plants m-2) compared to 3% and 6% CM hydromulch (48 and 66 plants m-2, respectively). Variables measured included weed density (measured at peak emergence and peak growth), weed dry biomass (measured at peak growth), onion bulb yield, onion leaf chlorophyll (measured using a SPAD meter), onion bulb Brix (measured using a Brix meter with onion bulb juice), percentage mulch deterioration (esimated visually), soil moisture and temperature (measured continuously throughoput the growing season using Meter 'Teros 11' sensors installed at 20 deep in the soil), and canopy temperature (measured continuously throughout the growing season with 'Hobo' pendant sensors). Hydromulches effectively reduced weed dry biomass, except 6% CM, compared to weedy check. Mulch deterioration was zero for PE mulch and GG formulations were the most durable hydromulch, with only 2-3% soil exposure at the end of the growing season. Onion yield was greater in PE mulch compared to CM hydromulches and weedy check at both locations. However, GG formulations showed similar onion yield as PE mulch at Fargo. In summary, the outcomes from this study confirmed the potential of GG-based hydromulches with guar gum tackifier as a sustainable and effective alternative to PE mulch in organic onion production.